chapter 2 part b: general engine overhaul procedures overhaul - general information . . . . . . . ....

22
2B General Cylinder compression pressure (all engines) . . . . . . . . . . . . . . . . . . . . . 10 to 11 bars Oil pressure (all engines) At idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 2.0 bars Running (for example, at 4000 rpm) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 bars or above (typically) Cylinder head warpage limit Except M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.10 mm M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 mm Minimum cylinder head thickness (do not resurface the head to a thickness less than listed) M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128.6 mm M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.7 mm M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140.55 mm Valves Valve stem diameter (standard) M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 mm M20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 mm M40 engine Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.975 mm Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.960 mm Minimum valve margin width Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.191 mm Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.98 mm Valve stem maximum lateral movement (see text) . . . . . . . . . . . . . . . . . 0.787 mm Valve face angle Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45° Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45° Chapter 2 Part B: General engine overhaul procedures Compression check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Crankshaft - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Crankshaft - refitting and main bearing oil clearance check . . . . . . . 24 Crankshaft - removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Crankshaft rear oil seal - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Cylinder head and components - cleaning and inspection . . . . . . . 9 Cylinder head - dismantling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Cylinder head - reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Cylinder honing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Engine - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Engine block - cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Engine block - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Engine overhaul - alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Engine overhaul - dismantling sequence . . . . . . . . . . . . . . . . . . . . . 7 Engine overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2 Engine overhaul - reassembly sequence . . . . . . . . . . . . . . . . . . . . . 21 Engine removal - methods and precautions . . . . . . . . . . . . . . . . . . . 4 General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Initial start-up and break-in after overhaul . . . . . . . . . . . . . . . . . . . . 27 Intermediate shaft - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 Intermediate shaft - removal and inspection . . . . . . . . . . . . . . . . . . . 14 Main and connecting big-end bearings - inspection . . . . . . . . . . . . 20 Piston rings - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 Pistons/connecting rods - inspection . . . . . . . . . . . . . . . . . . . . . . . . 18 Pistons/connecting rods - refitting and big-end bearing oil clearance check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Pistons/connecting rods - removal . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 2B•1 Easy, suitable for novice with little experience Fairly easy, suitable for beginner with some experience Fairly difficult, suitable for competent DIY mechanic Difficult, suitable for experienced DIY mechanic Very difficult, suitable for expert DIY or professional Degrees of difficulty Specifications Contents

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Page 1: Chapter 2 Part B: General engine overhaul procedures overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2 Engine overhaul - reassembly sequence

2B

GeneralCylinder compression pressure (all engines) . . . . . . . . . . . . . . . . . . . . . 10 to 11 barsOil pressure (all engines)

At idle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.5 to 2.0 barsRunning (for example, at 4000 rpm) . . . . . . . . . . . . . . . . . . . . . . . . . . 4 bars or above (typically)

Cylinder head warpage limitExcept M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.10 mm M40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 mm

Minimum cylinder head thickness (do not resurface the head to a thickness less than listed)M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128.6 mmM20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124.7 mmM40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140.55 mm

ValvesValve stem diameter (standard)

M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8.0 mmM20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.0 mmM40 engine

Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.975 mmExhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.960 mm

Minimum valve margin widthIntake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.191 mmExhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.98 mm

Valve stem maximum lateral movement (see text) . . . . . . . . . . . . . . . . . 0.787 mmValve face angle

Intake . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45°Exhaust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45°

Chapter 2 Part B:General engine overhaul procedures

Compression check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3Crankshaft - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19Crankshaft - refitting and main bearing oil clearance check . . . . . . . 24Crankshaft - removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13Crankshaft rear oil seal - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . 25Cylinder head and components - cleaning and inspection . . . . . . . 9Cylinder head - dismantling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8Cylinder head - reassembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11Cylinder honing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Engine - removal and refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5Engine block - cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15Engine block - inspection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16Engine overhaul - alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6Engine overhaul - dismantling sequence . . . . . . . . . . . . . . . . . . . . . 7

Engine overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2Engine overhaul - reassembly sequence . . . . . . . . . . . . . . . . . . . . . 21Engine removal - methods and precautions . . . . . . . . . . . . . . . . . . . 4General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1Initial start-up and break-in after overhaul . . . . . . . . . . . . . . . . . . . . 27Intermediate shaft - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23Intermediate shaft - removal and inspection . . . . . . . . . . . . . . . . . . . 14Main and connecting big-end bearings - inspection . . . . . . . . . . . . 20Piston rings - refitting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22Pistons/connecting rods - inspection . . . . . . . . . . . . . . . . . . . . . . . . 18Pistons/connecting rods - refitting and big-end bearing oil

clearance check . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Pistons/connecting rods - removal . . . . . . . . . . . . . . . . . . . . . . . . . . 12Valves - servicing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

2B•1

Easy, suitable fornovice with littleexperience

Fairly easy, suitablefor beginner withsome experience

Fairly difficult,suitable for competentDIY mechanic

Difficult, suitable forexperienced DIYmechanic

Very difficult,suitable for expertDIY or professional

Degrees of difficulty

Specifications

Contents

Page 2: Chapter 2 Part B: General engine overhaul procedures overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2 Engine overhaul - reassembly sequence

Camshaft and rocker armsCamshaft bearing oil clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.033 to 0.076 mmCamshaft endfloat

M10 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.13 mmM20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.2 mm maximumM30 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.18 mmM40 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.065 to 0.150 mm

Rocker arm radial clearance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.015 to 0.051 mm

CrankshaftEndfloat

M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.085 to 0.174 mmM20 and M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.080 to 0.163 mm

Main bearing journal diameter (standard)M10 engines

Red classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.98 to 54.99 mmBlue classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54.97 to 54.98 mm

M20 enginesRed classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.98 to 59.99 mmBlue classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.97 to 59.98 mm

M30 and M40 enginesYellow classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.984 to 59.990 mmGreen classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.977 to 59.983 mmWhite classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59.971 to 59.976 mm

Main bearing journal diameter undersizes1st undersize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25 mm2nd undersize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.50 mm3rd undersize (where applicable) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.75 mm

Main bearing oil clearanceM10 and M20 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.030 to 0.070 mmM30 and M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.020 to 0.046 mm

Connecting rod journal diameter (standard)M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47.975 to 47.991 mmM20 and M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44.975 to 44.991 mm

Connecting rod journal diameter undersizes1st undersize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25 mm2nd undersize . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.50 mm3rd undersize (where applicable) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.75 mm

Connecting rodsConnecting rod side play (all engines) . . . . . . . . . . . . . . . . . . . . . . . . . . 0.041 mmConnecting big-end bearing oil clearance

M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.030 to 0.070 mmM20 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.020 to 0.055 mmM40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.010 to 0.052 mm

Engine blockCylinder bore - diameter (standard)

M10/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89.00 to 89.01 mmM20/B20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80.00 to 80.01 mmM20/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.00 to 84.01 mmM30/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86.00 to 86.01 mmM30/B28 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86.00 to 86.01 mmM30/B30M engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89.00 to 89.01 mmM30/B34 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 00 to 92.01 mmM30/B35M engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92.00 to 92.01 mmM40/B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.000 to 84.014 mmM40/B18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.000 to 84.014 mm

Cylinder out-of-round limit (maximum)M20/B20 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 mmM20/B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 mmAll other engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01 mm

Cylinder taper (maximum)M20/B20 and M20/B25 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 mmAll other engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01 mm

2B•2 General engine overhaul procedures

Page 3: Chapter 2 Part B: General engine overhaul procedures overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2 Engine overhaul - reassembly sequence

Pistons and piston ringsPiston diameter (standard)

M10 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88.97 mmM20 engines

B20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79.98 mmB25 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.98 mm

M30 enginesB30M

Alcan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88.970 mmKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88.980 mm

B35MAlcan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.972 mmMahle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91.980 mm

M40 enginesFactory stage 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83.985 mmFactory stage 00 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84.065 mm

Piston-to-cylinder wall clearanceNew

M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.05 mmM20 and M40 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.01 to 0.04 mm

Service limitExcept B25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.15 mmB25 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.12 mm

Piston ring end gapM10 engine

Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 to 0.70 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.40 mmOil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.25 to 0.50 mm

M20 engineAll rings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.50 mm

M30 engineTop compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 0.45 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 to 0.65 mmOil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.30 to 0.60 mm

M40 engineTop compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 1.00 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 1.00 mmOil ring

B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.20 to 1.00 mmB18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.40 to 1.40 mm

Piston ring side clearanceM10 engine

Top compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.06 to 0.09 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.072 mmOil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.06 mm

M20 engineTop compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.04 to 0.08 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.07 mmOil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.05 mm

M30 engineTop compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.04 to 0.072 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.03 to 0.062 mmOil ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.055 mm

M40 engineTop compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.20 mmSecond compression ring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.10 mmOil ring

B16 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 0.02 to 0.10 mmB18 engine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Not measured

Torque wrench settings NmMain bearing cap-to-engine block bolts*

M10, M20 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60M40 engines

Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 50°

General engine overhaul procedures 2B•3

2B

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Torque wrench settings (continued) NmConnecting rod cap bolts/nuts

M10 and M30 engines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55M20 and M40 engines

Stage 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20Stage 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Angle-tighten an additional 70°

Camshaft bearing caps (M40 engine) . . . . . . . . . . . . . . . . . . . . . . . . . . . 10Intermediate shaft sprocket-to-shaft bolt (M20 engine) . . . . . . . . . . . . . 60Oil supply tube bolt(s)

M6 (normal) and M8 (banjo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10M5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

* BMW recommend that the main bearing bolts are renewed as a matter of course.

2B•4 General engine overhaul procedures

1 General information

Included in this Part of Chapter 2 are thegeneral overhaul procedures for the cylinderhead and engine internal components.

The information ranges from adviceconcerning preparation for an overhaul andthe purchase of new parts to detailed,paragraph-by-paragraph procedures coveringremoval and refitting of internal componentsand the inspection of parts.

The following Sections have been writtenbased on the assumption that the engine hasbeen removed from the vehicle. Forinformation concerning in-vehicle enginerepair, as well as removal and refitting of theexternal components necessary for theoverhaul, see Chapter 2A, and Section 7 ofthis Part.

The Specifications included in this Part areonly those necessary for the inspection andoverhaul procedures which follow. Refer toPart A for additional Specifications.

2 Engine overhaul - general information

It’s not always easy to determine when, orif, an engine should be completelyoverhauled, as a number of factors must beconsidered.

High mileage is not necessarily anindication that an overhaul is needed, whilelow mileage doesn’t preclude the need for anoverhaul. Frequency of servicing is probablythe most important consideration. An enginethat’s had regular and frequent oil and filterchanges, as well as other requiredmaintenance, will most likely give manythousands of miles of reliable service.Conversely, a neglected engine may requirean overhaul very early in its life.

Excessive oil consumption is an indicationthat piston rings, valve seals and/or valveguides are in need of attention. Make surethat oil leaks aren’t responsible beforedeciding that the rings and/or guides areworn. Perform a cylinder compression checkto determine the extent of the work required(see Section 3).

Check the oil pressure: Unscrew the oilpressure sender unit, and connect an oilpressure gauge in its place. Measure the oilpressure with the engine at its normaloperating temperature. Compare yourreadings to the oil pressures listed in thisChapter’s Specifications. If the readings aresignificantly below these (and if the oil and oilfilter are in good condition), the crankshaftbearings and/or the oil pump are probablyworn out. On M10 and M30 engines, the oilpressure sender unit is located high on the leftrear of the cylinder head. On M20 engines, thesender unit is threaded into the side of theengine block, below the oil filter. On M40engines, the sender unit is threaded into therear of the oil filter housing.

Loss of power, rough running, knocking ormetallic engine noises, excessive valve trainnoise and high fuel consumption may alsopoint to the need for an overhaul, especially ifthey’re all present at the same time. If acomplete tune-up doesn’t remedy thesituation, major mechanical work is the onlysolution.

An engine overhaul involves restoring theinternal parts to the specifications of a newengine. During an overhaul, new piston ringsare fitted and the cylinder walls arereconditioned (rebored and/or honed). If arebore is done by an engineering works, newoversize pistons will also be fitted. The mainbearings and connecting big-end bearings aregenerally renewed and, if necessary, thecrankshaft may be reground to restore thejournals. Generally, the valves are serviced aswell, since they’re usually in less-than-perfectcondition at this point. While the engine isbeing overhauled, other components, such asthe distributor, starter and alternator, can berebuilt as well. The end result should be a like-new engine that will give many thousands oftrouble-free miles. Note: Critical coolingsystem components such as the hoses,drivebelts, thermostat and water pump MUSTbe renewed when an engine is overhauled.The radiator should be checked carefully, toensure that it isn’t clogged or leaking (seeChapters 1 or 3). Also, we don’t recommendoverhauling the oil pump - always fit a newone when an engine is rebuilt.

Before beginning the engine overhaul, readthrough the entire procedure to familiariseyourself with the scope and requirements of

the job. Overhauling an engine isn’t difficult ifyou follow all of the instructions carefully,have the necessary tools and equipment andpay close attention to all specifications;however, it is time consuming. Plan on thevehicle being tied up for a minimum of twoweeks, especially if parts must be taken to anautomotive machine shop for repair or recon-ditioning. Check on availability of parts andmake sure that any necessary special toolsand equipment are obtained in advance. Mostwork can be done with typical hand tools,although a number of precision measuringtools are required for inspecting parts todetermine if they must be replaced. Often anautomotive machine shop will handle theinspection of parts and offer adviceconcerning reconditioning and renewal. Note:Always wait until the engine has beencompletely disassembled and all components,especially the engine block, have beeninspected before deciding what service andrepair operations must be performed by anautomotive machine shop. Since the block’scondition will be the major factor to considerwhen determining whether to overhaul theoriginal engine or buy a rebuilt one, neverpurchase parts or have machine work done onother components until the block has beenthoroughly inspected. As a general rule, timeis the primary cost of an overhaul, so it doesn’tpay to refit worn or substandard parts.

As a final note, to ensure maximum life andminimum trouble from a rebuilt engine,everything must be assembled with care, in aspotlessly-clean environment.

3 Compression check 21 A compression check will tell you whatmechanical condition the upper end (pistons,rings, valves, head gaskets) of your engine isin. Specifically, it can tell you if thecompression is down due to leakage causedby worn piston rings, defective valves andseats, or a blown head gasket. Note: Theengine must be at normal operatingtemperature, and the battery must be fully-charged, for this check. 2 Begin by cleaning the area around thespark plugs before you remove them(compressed air should be used, if available,

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otherwise a small brush or even a bicycle tyrepump will work). The idea is to prevent dirtfrom getting into the cylinders as thecompression check is being done.3 Remove all the spark plugs from the engine(see Chapter 1).4 Block the throttle wide open, or have anassistant hold the throttle pedal down.5 On carburettor models, disconnect the LTlead from the coil. On fuel injection models,disable the fuel pump and ignition circuit byremoving the main relay (see illustration).This is to avoid the possibility of a fire fromfuel being sprayed in the enginecompartment. The location of the main relay isgenerally near the fuse panel area under thebonnet, but refer to Chapter 12 for thespecific location on your model.6 Fit the compression gauge in the No 1spark plug hole (No 1 cylinder is nearest theradiator).7 Turn the engine on the starter motor over atleast seven compression strokes, and watchthe gauge. The compression should build upquickly in a healthy engine. Low compressionon the first stroke, followed by gradually-increasing pressure on successive strokes,indicates worn piston rings. A lowcompression reading on the first stroke, whichdoesn’t build up during successive strokes,indicates leaking valves or a blown headgasket (a cracked head could also be thecause). Deposits on the undersides of thevalve heads can also cause low compression.Record the highest gauge reading obtained.8 Repeat the procedure for the remainingcylinders, and compare the results to thecompression listed in this Chapter’s Specifi-cations.9 If compression was low, add some engineoil (about three squirts from a plunger-type oilcan) to each cylinder, through the spark plughole, and repeat the test.10 If the compression increases after the oilis added, the piston rings are definitely worn.If the compression doesn’t increase

significantly, the leakage is occurring at thevalves or head gasket. Leakage past thevalves may be caused by burned valve seatsand/or faces or warped, cracked or bentvalves.11 If two adjacent cylinders have equally lowcompression, there’s a strong possibility thatthe head gasket between them is blown. Theappearance of coolant in the combustionchambers or the crankcase would verify thiscondition.12 If one cylinder is 20 percent lower than theothers, and the engine has a slightly roughidle, a worn exhaust lobe on the camshaftcould be the cause.13 If the compression is unusually high, thecombustion chambers are probably coatedwith carbon deposits. If that’s the case, thecylinder head should be removed anddecarbonised.14 If compression is way down, or variesgreatly between cylinders, it would be a goodidea to have a leak-down test performed by agarage. This test will pinpoint exactly where the leakage is occurring and howsevere it is.

4 Engine removal - methods and precautions

If you’ve decided that an engine must beremoved for overhaul or major repair work,several preliminary steps should be taken.

Locating a suitable place to work isextremely important. Adequate work space,along with storage space for the vehicle, willbe needed. If a workshop or garage isn’tavailable, at the very least a flat, level, cleanwork surface made of concrete or asphalt isrequired.

Cleaning the engine compartment andengine before beginning the removalprocedure will help keep tools clean andorganised.

An engine hoist or A-frame will also benecessary. Make sure the equipment is ratedin excess of the combined weight of theengine and accessories. Safety is of primaryimportance, considering the potential hazardsinvolved in lifting the engine out of the vehicle.

If the engine is being removed by a novice,a helper should be available. Advice and aidfrom someone more experienced would alsobe helpful. There are many instances whenone person cannot simultaneously perform allof the operations required when lifting theengine out of the vehicle.

Plan the operation ahead of time. Arrangefor or obtain all the tools and equipment you’llneed prior to beginning the job. Some of theequipment necessary to perform engineremoval and refitting safely and with relativeease are (in addition to an engine hoist) aheavy-duty trolley jack, complete sets ofspanners and sockets as described in the

front of this manual, wooden blocks, andplenty of rags and cleaning solvent formopping up spilled oil, coolant and fuel. If thehoist must be hired, make sure that youarrange for it in advance, and perform all ofthe operations possible without it beforehand.This will save you money and time.

Plan for the vehicle to be out of use forquite a while. A machine shop will be requiredto perform some of the work which the do-it-yourselfer can’t accomplish without specialequipment. These establishments often havea busy schedule, so it would be a good ideato consult them before removing the engine,in order to accurately estimate the amount oftime required to rebuild or repair componentsthat may need work.

Always be extremely careful when removingand refitting the engine. Serious injury canresult from careless actions. Plan ahead, takeyour time and a job of this nature, althoughmajor, can be accomplished successfully.

Warning: The air conditioningsystem is under high pressure.Do not loosen any fittings orremove any components until

after the system has been discharged by aqualified engineer. Always wear eyeprotection when disconnecting airconditioning system fittings.

Caution: If removing the M40engine, it is important not to turnthe engine upside-down forlonger than 10 minutes since it is

possible for the oil to drain out of thehydraulic tappets. This would render thetappets unserviceable, and damage couldpossibly occur to the engine when it isnext started up.

5 Engine - removal and refitting 3Caution: If the radio in yourvehicle is equipped with an anti-theft system, make sure you

have the correct activation code beforedisconnecting the battery.Note: If, after connecting the battery, thewrong language appears on the instrumentpanel display, refer to page 0-7 for thelanguage resetting procedure.

Removal1 Relieve the fuel system pressure (seeChapter 4), then disconnect the negativecable from the battery. 2 Cover the wings and front panel, andremove the bonnet (see Chapter 11). Specialpads are available to protect the wings, but anold bedspread or blanket will also work.3 Remove the air cleaner housing and intakeducts (see Chapter 4).4 Drain the cooling system (see Chapter 1).5 Label the vacuum lines, emissions systemhoses, wiring connectors, earth straps andfuel lines, to ensure correct refitting, then

General engine overhaul procedures 2B•5

3.5 As a safety precaution, beforeperforming a compression check, remove

the cover and the main relay (arrowed)from the left side of the engine

compartment to disable the fuel andignition systems (525i model shown, other

models similar)

2B

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detach them. Pieces of masking tape withnumbers or letters written on them work well(see illustration).

6 Label and detach all coolant hoses from theengine (see Chapter 3).7 Remove the cooling fan, shroud andradiator (see Chapter 3). Note: On the M40engine, it is only necessary to remove thecooling fan and shroud; however, preventdamage to the radiator by covering it with apiece of wood or cardboard.8 Remove the drivebelts (see Chapter 1).9 Disconnect the fuel lines from the fuel rail(see Chapter 4).

Warning: Fuel is extremelyflammable, so take extraprecautions when you work onany part of the fuel system. Don’t

smoke, or allow open flames or bare lightbulbs, near the work area, and don’t workin a garage where a natural gas-typeappliance (such as a water heater orclothes dryer) with a pilot light is present.If you spill any fuel on your skin, rinse it offimmediately with soap and water. Whenyou perform any kind of work on the fuelsystem, wear safety glasses, and have afire extinguisher on hand.10 Disconnect the accelerator cable (seeChapter 4) and kickdown linkage/speedcontrol cable (see Chapter 7B), if applicable,from the engine.11 Where fitted, unbolt the power steeringpump (see Chapter 10). Leave the lines/hosesattached, and make sure the pump is kept inan upright position in the engine compartment(use wire or rope to restrain it out of the way).12 On air-conditioned models, unbolt thecompressor (see Chapter 3) and set it aside,or tie it up out of the way. Do not disconnectthe hoses.13 Drain the engine oil (see Chapter 1) andremove the filter. Remove the engine splashguard from under the engine.14 Remove the starter motor (see Chapter 5).

15 Remove the alternator (see Chapter 5).This is not essential on all models, but it is agood idea in any case to avoid accidentaldamage.16 Unbolt the exhaust system from theengine (see Chapter 4).17 If you’re working on a vehicle with anautomatic transmission, remove the torqueconverter-to-driveplate fasteners (seeChapter 7B). On the M40 engine, unbolt theautomatic transmission fluid coolant pipesfrom the sump.18 Support the transmission with a jack.Position a block of wood between them, toprevent damage to the transmission. Specialtransmission jacks with safety chains areavailable - use one if possible.19 Attach an engine sling or a length of chainto the lifting brackets on the engine. If thebrackets have been removed, the chain canbe bolted directly to the intake manifold studs,but place a flat washer between the chain andthe nut, and tighten the nut all the way up tothe chain, to avoid the possibility of the studsbending.20 Roll the hoist into position and connectthe sling to it. Take up the slack in the sling orchain, but don’t lift the engine.

Warning: DO NOT place any partof your body under the enginewhen it’s supported only by ahoist or other lifting device.

21 On M10, M20 and M30 engines, removethe transmission rear crossmember, andslightly lower the rear of the transmission.22 Remove the transmission-to-engine blockbolts using a Torx socket. Note: The boltsholding the bellhousing to the engine blockwill require a swivel at the socket, and a verylong extension going back towards thetransmission.23 Remove the engine mounting-to-framebracket nuts. On the M40 engine, unbolt thedampers from the mountings.24 Recheck to be sure nothing is stillconnecting the engine to the transmission orvehicle. Disconnect anything still remaining.25 Raise the engine slightly. Carefully work itforwards to separate it from the transmission.If you’re working on a vehicle with anautomatic transmission, you may find thetorque converter comes forward with the

engine. If it stays with the transmission, leaveit, but you may find it easier to let it comeforward until it can be grasped easier and bepulled from the crankshaft. Note: Whenrefitting the torque converter to thetransmission before the engine is refitted, besure to renew the transmission front pumpseal, which will probably be damaged whenthe converter comes out with the engine.Either method is acceptable, but be preparedfor some fluid to leak from the torqueconverter if it comes out of the transmission. Ifyou’re working on a vehicle with a manualtransmission, draw the engine forwards untilthe input shaft is completely disengaged fromthe clutch. Slowly raise the engine out of theengine compartment. Check carefully to makesure everything is disconnected.26 Remove the flywheel/driveplate (andwhere applicable, the engine rear plate), andmount the engine on an engine stand (seeillustration). Do not turn the M40 engineupside-down (see Caution in Section 4).

Refitting27 Check the engine and transmissionmountings. If they’re worn or damaged, renewthem.28 Refit the flywheel or driveplate (seeChapter 2A). If you’re working on a manualtransmission vehicle, refit the clutch andpressure plate (see Chapter 7A). Now is agood time to fit a new clutch.29 If the torque converter came out with theengine during removal, carefully refit theconverter into the transmission before theengine is lowered into the vehicle.30 Carefully lower the engine into the enginecompartment - make sure the enginemountings line up.31 If you’re working on an automatictransmission vehicle, guide the torqueconverter onto the crankshaft following theprocedure outlined in Chapter 7B.32 If you’re working on a manualtransmission vehicle, apply a dab of high-melting-point grease to the input shaft, andguide it into the clutch and crankshaft pilotbearing until the bellhousing is flush with theengine block.. Do not allow the weight of theengine to hang on the input shaft.

33 Refit the transmission-to-engine bolts,and tighten them securely.

Caution: DO NOT use the bolts toforce the transmission andengine together.

34 Refit the remaining components in thereverse order of removal.35 Add coolant, oil, power steering andtransmission fluid as needed.

2B•6 General engine overhaul procedures

5.26 Removing the engine rear plate - M40 engine

5.5 Label each wire before unplugging theconnector

If there’s any possibility ofconfusion, make a sketch ofthe engine compartment andclearly label the lines, hosesand wires.

It may be necessary to rockthe engine slightly, or to turnthe crankshaft, to allow theinput shaft splines to matewith the clutch plate

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36 Run the engine and check for leaks andproper operation of all accessories, then refitthe bonnet and test drive the vehicle.37 Where necessary, have the airconditioning system recharged and leak-tested.

6 Engine overhaul - alternatives

The do-it-yourselfer is faced with a numberof options when performing an engineoverhaul. The decision to renew the engineblock, piston/connecting rod assemblies andcrankshaft depends on a number of factors,with the number one consideration being thecondition of the block. Other considerationsare cost, access to machine shop facilities,parts availability, time required to completethe project, and the extent of prior mechanicalexperience on the part of the do-it-yourselfer.

Some of the alternatives include:Individual parts - If the inspection

procedures reveal that the engine block andmost engine components are in re-usablecondition, purchasing individual parts may bethe most economical alternative. The block,crankshaft and piston/connecting rodassemblies should all be inspected carefully.Even if the block shows little wear, thecylinder bores should be surface-honed.

Crankshaft kit - A crankshaft kit (whereavailable) consists of a reground crankshaftwith matched undersize new main andconnecting big-end bearings. Sometimes,reconditioned connecting rods and newpistons and rings are included with the kit(such a kit is sometimes called an “enginekit”). If the block is in good condition, but thecrankshaft journals are scored or worn, acrankshaft kit and other individual parts maybe the most economical alternative.

Short block - A short block consists of anengine block with a crankshaft andpiston/connecting rod assemblies alreadyfitted. New bearings are fitted, and allclearances will be correct. The existingcamshaft, valve train components, cylinderhead and external parts can be bolted to theshort block with little or no machine shopwork necessary.

Full block - A “full” or “complete” blockconsists of a short block plus an oil pump,sump, cylinder head, valve cover, camshaftand valve train components, timing sprocketsand chain (or belt) and timing cover. Allcomponents are fitted with new bearings,seals and gaskets used throughout. Therefitting of manifolds and external parts is allthat’s necessary.

Give careful thought to which alternative isbest for you, and discuss the situation withlocal machine shops, parts dealers andexperienced rebuilders before ordering orpurchasing new parts.

7 Engine overhaul - dismantling sequence

1 It’s much easier to dismantle and work onthe engine if it’s mounted on a portableengine stand. A stand can often be hired quitecheaply from a tool hire shop. Before theengine is mounted on a stand, theflywheel/driveplate should be removed fromthe engine.2 If a stand isn’t available, it’s possible todismantle the engine with it blocked up on thefloor. Be extra-careful not to tip or drop theengine when working without a stand.3 If you’re going to obtain a rebuilt engine, allthe external components listed below mustcome off first, to be transferred to the newengine if applicable. This is also the case ifyou’re doing a complete engine overhaulyourself. Note: When removing the externalcomponents from the engine, pay closeattention to details that may be helpful orimportant during refitting. Note the fittedposition of gaskets, seals, spacers, pins,brackets, washers, bolts and other small items.

Alternator and bracketsEmissions control componentsDistributor, HT leads and spark plugsThermostat and housing coverWater pumpFuel injection/carburettor and fuel systemcomponentsIntake and exhaust manifoldsOil filter and oil pressure sending unitEngine mounting brackets (see illustration)Clutch and flywheel/driveplateEngine rear plate (where applicable)

4 If you’re obtaining a short block, whichconsists of the engine block, crankshaft,pistons and connecting rods all assembled,then the cylinder head, sump and oil pumpwill have to be removed as well. See Section 6for additional information regarding thedifferent possibilities to be considered.5 If you’re planning a complete overhaul, theengine must be dismantled and the internalcomponents removed in the following generalorder:

Valve coverIntake and exhaust manifoldsTiming belt or chain coversTiming chain/beltWater pumpCylinder headSumpOil pumpPiston/connecting rod assembliesCrankshaft and main bearingsCamshaftRocker shafts and rocker arms (M10, M20and M30 engines)Cam followers and hydraulic tappets (M40 engine)Valve spring retainers and springsValves

6 Before beginning the dismantling and

overhaul procedures, make sure the followingitems are available. Also, refer to Section 21for a list of tools and materials needed forengine reassembly.

Common hand toolsSmall cardboard boxes or plastic bags forstoring partsCompartment-type metal box for storingthe hydraulic tappets (M40 engine)Gasket scraperRidge reamerVibration damper pullerMicrometersTelescoping gaugesDial indicator setValve spring compressorCylinder surfacing honePiston ring groove cleaning toolElectric drill motorTap and die setWire brushesOil gallery brushesCleaning solvent

8 Cylinder head - dismantling 41 Remove the cylinder head (see Chapter 2A).2 Remove the oil supply tube from itsmounting on top of the cylinder head (seeillustrations). Note: It’s important to renewthe seals under the tube mounting bolts.

General engine overhaul procedures 2B•7

7.3 Engine left-hand mounting bracket -M40 engine

8.2a Remove the oil tube from the top ofthe cylinder head (M10 engine). Be sure to

note the location of all gaskets andwashers for reassembly

2B

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M10, M20 and M30 engines3 Adjust all valves to their maximum clearanceby rotating the eccentric on the valve end ofthe rocker arm towards the centre of the head(see Chapter 1, if necessary).4 Before removing the thrustplate, measurethe camshaft endfloat by mounting a dialindicator to the front end of the cylinder head,with the probe resting on the camshaft (seeillustration). Prise the camshaft back-and-forth in the cylinder head. The reading is thecamshaft endfloat. Compare the reading tothis Chapter’s Specifications.5 Unbolt and remove the camshaftthrustplate. Note: There are two differentlocations for the thrustplate. On M10 and M30engines, it is attached on the front of thecylinder head, behind the timing gear flange.On M20 and M40 engines, the thrustplate islocated inside the head, by the rocker shafts,at the forward end of the cylinder head.6 Remove the rear cover plate from the backof the cylinder head (see illustration).7 Remove the retaining clips from each of therocker arms. Note: There is more than onestyle of clip. The wire-type clips (seeillustration) are fitted one each side of therocker arm; the spring-steel-type goes overthe rocker arm, and clips onto either side of it.8 Before removing the rocker arm shafts,measure the rocker arm radial clearance,using a dial indicator, and compare yourmeasurement to the Specifications at the

beginning of this Chapter. Without sliding therocker arm along the shaft, try to rotate therocker arm against the shaft in each direction(see illustration). The total movementmeasured at the camshaft end of the rockerarm is the radial clearance. If the clearance isexcessive, either the rocker arm bush, rockerarm shaft, or both, will need to be renewed.9 Remove the rubber retaining plugs, or thethreaded plugs, at the front of the cylinderhead, as applicable. There is a plug in front ofeach rocker shaft.

Caution: If your engine haswelded-in retaining plugs at thefront of the rocker shafts, takethe cylinder head to a machine

shop for plug removal, to avoid possibledamage to the cylinder head or the rockerarm shafts.10 Rotate the camshaft until the most rockerarms possible are loose (not compressingtheir associated valve springs).11 For the remaining rocker arms that are stillcompressing their valve springs, BMWrecommends using a special forked tool tocompress the rocker arms against the valvesprings (and therefore take the valve springtension off the camshaft lobe). If the tool is notavailable, insert a standard screwdriver into thegap above the adjuster eccentric at the valve-end tip of each rocker arm. Using the

screwdrivers, prise the rocker arms against thevalve springs, and hold them in place as thecamshaft is removed (see the next paragraph).At least one assistant will be necessary for thisoperation, since three or four valve springsusually need compressing. If no assistance isavailable, you could try retaining thescrewdrivers that are compressing the valvesprings to the bench with lengths of sturdy wire.

Warning: Be sure the wire issecurely attached to the benchand screwdrivers, or the

screwdrivers could fly off the cylinderhead, possibly causing injury.12 When all the rocker arms are no longercontacting the camshaft lobes, slowly andcarefully pull the camshaft out the front of thecylinder head. It may be necessary to rotatethe camshaft as it is removed.

Caution: Be very careful not toscratch the camshaft bearingjournals in the cylinder head asthe camshaft is withdrawn.

13 After removing the camshaft, carefullyremove the rocker arm shafts. On modelswithout threaded holes at the front of theshafts, drive them out from the rear of thecylinder head with a hammer and hardwooddowel that is slightly smaller in diameter thanthe rocker arm shaft (see illustration). For

2B•8 General engine overhaul procedures

8.13 Removing a rocker arm shaft fromthe front of the cylinder head - the shaft

must be either driven out from the rear ofthe head with a hardwood dowel or, on

models where the rocker shaft is threadedat the front, pulled out from the front with

a slide-hammer-type puller

8.8 Check the rocker arm-to-shaft radialclearance by setting up a dial indicator asshown, and trying to rotate the rocker armagainst the shaft - DO NOT slide the rocker

arm along the shaft

8.7 Remove the retaining clips from therocker arms - the wire-type clip is shown

here

8.6 Remove the cover from the rear of thecylinder head - be sure to note the

locations of any washers, gaskets andseals while you are removing the cover

8.4 To check camshaft endfloat, mount adial indicator so that its stem is in-line with

the camshaft and just touching thecamshaft at the front

8.2b Removing the oil tube from thecamshaft bearing caps on the top of the

cylinder head (M40 engine)

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rocker shafts with a threaded front hole,screw in a slide hammer to pull the shaft fromthe head.14 As each rocker arm shaft is slid out of thecylinder head, the rocker arms will bereleased, one by one.15 Drop each rocker arm into a labelled bag,so they can be returned to their originallocations on reassembly. While you’reremoving the rocker arm shafts, note theirorientation. The guide plate notches and thesmall oil holes face in; the large oil holes facedown, toward the valve guides. Also, label therocker shafts so they can be returned to theiroriginal locations in the cylinder head.

M40 enginesCaution: Keep the cylinder headupright until all of the hydraulictappets have been removed. Ifthis precaution is not taken, the

oil may drain out of the tappets and renderthem unserviceable.16 Check that the camshaft bearing caps arenumbered or identified for location.17 Progressively unscrew and remove thecamshaft bearing cap retaining bolts, thenremove the caps (see illustrations).18 Lift the camshaft from the top of thecylinder head, and remove the oil seal fromthe timing end.19 Have ready a compartmentalised boxfilled with engine oil to receive the hydraulictappets so that they are kept identified fortheir correct location (see illustration). Alsohave a further box ready to receive the camfollowers.

20 Remove the cam followers and thrustdiscs, then lift out the hydraulic tappets fromtheir bores in the cylinder head (seeillustrations).

All engines21 Before the valves are removed, arrange tolabel and store them, along with their relatedcomponents, so they can be kept separateand reinstalled in the same valve guides fromwhich they’re removed (see illustration).22 Compress the springs on the first valvewith a spring compressor, and remove thecollets (see illustration). Carefully release thevalve spring compressor, and remove theretainer, the spring and the spring seat (ifused). 23 Pull the valve out of the head, thenremove the oil seal from the guide.

General engine overhaul procedures 2B•9

8.19 Compartmentalised box to hold thehydraulic tappets (M40 engine)

8.17b . . . and camshaft - M40 engine8.17a Removing the camshaft bearingcaps . . .

8.22 Using a valve spring compressor tocompress a valve spring

8.21 A small plastic bag, with anappropriate label, can be used to store the

valve components so they can be kepttogether and refitted in the original position

8.20b . . . and thrust discs . . .8.20a Remove the cam followers . . .

8.20c . . . then lift out the hydraulic tappets

2B

If the valve binds in the guide (won’tpull through), push it back into thehead, and deburr the area around thecollet groove with a fine file orwhetstone.

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24 Repeat the procedure for the remainingvalves. Remember to keep all the parts foreach valve together, so they can be refitted inthe same locations.25 Once the valves and related componentshave been removed and stored in anorganised manner, the head should bethoroughly cleaned and inspected. If acomplete engine overhaul is being done,finish the engine dismantling proceduresbefore beginning the cylinder head cleaningand inspection process.

9 Cylinder head andcomponents - cleaning and inspection

41 Thorough cleaning of the cylinder head(s)and related valve train components, followedby a detailed inspection, will enable you todecide how much valve service work must bedone during the engine overhaul. Note: If theengine was severely overheated, the cylinderhead is probably warped (see paragraph 10).

Cleaning2 Scrape all traces of old gasket material andsealing compound off the cylinder head,intake manifold and exhaust manifold sealingsurfaces. Be very careful not to gouge thecylinder head. Special gasket removalsolvents are available at motor factors.3 Remove all built-up scale from the coolantpassages.4 Run a stiff brush through the various holesto remove deposits that may have formed inthem.5 Run an appropriate-size tap into each of thethreaded holes, to remove corrosion andthread sealant that may be present. Ifcompressed air is available, use it to clear theholes of debris produced by this operation.

Warning: Wear eye protectionwhen using compressed air!

6 Clean the cylinder head with solvent, anddry it thoroughly. Compressed air will speedthe drying process, and ensure that all holes

and recessed areas are clean. Note:Decarbonising chemicals are available, andmay prove very useful when cleaning cylinderheads and valve train components. They arevery caustic, however, and should be usedwith caution. Be sure to follow the instructionson the container.7 Clean all the rocker shafts/arms/followers,springs, valve springs, spring seats, keepersand retainers with solvent, and dry themthoroughly. Clean the components from onevalve at a time, to avoid mixing up the parts.

Caution: DO NOT clean thehydraulic tappets of the M40engine; leave them completelyimmersed in oil.

8 Scrape off any heavy deposits that mayhave formed on the valves, then use amotorised wire brush to remove deposits fromthe valve heads and stems. Again, make surethe valves don’t get mixed up.

InspectionNote: Be sure to perform all of the followinginspection procedures before concluding thatmachine shop work is required. Make a list ofthe items that need attention.

Cylinder head9 Inspect the head very carefully for cracks,evidence of coolant leakage, and otherdamage. If cracks are found, check with anmachine shop concerning repair. If repair isn’tpossible, a new cylinder head should beobtained.10 Using a straightedge and feeler gauge,check the head gasket mating surface forwarpage (see illustration). If the warpageexceeds the limit listed in this Chapter’sSpecifications, it may be possible to have itresurfaced at a machine shop, providing thehead is not reduced to less than the specifiedminimum thickness.11 Examine the valve seats in each of thecombustion chambers. If they’re badly pitted,cracked or burned, the head will requireservicing that’s beyond the scope of the homemechanic.

12 Check the valve stem-to-guide clearanceby measuring the lateral movement of thevalve stem with a dial indicator (seeillustration). The valve must be in the guideand approximately 2.0 mm off the seat. Thetotal valve stem movement indicated by thegauge needle must be divided by two, toobtain the actual clearance. After this is done,if there’s still some doubt regarding thecondition of the valve guides, they should bechecked by a machine shop (the cost shouldbe minimal).

Valves13 Carefully inspect each valve face foruneven wear, deformation, cracks, pits andburned areas (see illustration). Check thevalve stem for scuffing and the neck forcracks. Rotate the valve, and check for anyobvious indication that it’s bent. Look for pitsand excessive wear on the end of the stem.The presence of any of these conditionsindicates the need for valve service asdescribed in the next Section.14 Measure the margin width on each valve(see illustration). Any valve with a marginnarrower than specified will have to bereplaced with a new one.

Valve components15 Check each valve spring for wear on theends. The tension of all springs should bechecked with a special fixture before deciding

2B•10 General engine overhaul procedures

9.14 The margin width on each valve mustbe as specified (if no margin exists, the

valve cannot be reused)

9.13 Check for valve wear at the pointsshown here

9.12 A dial indicator can be used todetermine the valve stem-to-guide

clearance (move the valve as indicated bythe arrows)

9.10 Check the cylinder head gasketsurface for warpage by trying to slip a

feeler gauge under the straightedge (seethis Chapter’s Specifications for the

maximum warpage allowed, and use afeeler gauge of that thickness)

1 Valve tip2 Collet groove3 Stem (least-worn

area)

4 Stem (most-worn area)

5 Valve face6 Margin

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that they’re suitable for use in a rebuilt engine(take the springs to a machine shop for thischeck).16 Stand each spring on a flat surface, andcheck it for squareness (see illustration). Ifany of the springs are distorted or sagged, orpossibly have a broken coil, fit new parts.17 Check the spring retainers and keepersfor obvious wear and cracks. Anyquestionable parts should be renewed, asextensive damage will occur if they fail duringengine operation.

Rocker arms (M10, M20 and M30 engines)Note: The rocker arms for the exhaust valvesare the most subject to wear, and should bechecked with particular care.18 Inspect all the rocker arms for excessivewear on the tips that contact the valve stemand camshaft (see illustration). 19 Check the rocker arm radial clearance(see Section 8). If it’s excessive, either therocker arm bush or the shaft (or both) isexcessively worn. To determine which is moreworn, slide the rocker arm onto an unwornportion of the rocker arm shaft, and check theradial clearance again. If it’s now within speci-fications, the shaft is probably the most-worncomponent. If it’s not within specifications,the rocker arm bushes should be renewed.

Rocker arm shafts (M10, M20 andM30 engines)20 Check the shafts for scoring, excessivewear and other damage. The areas where the

rocker arms contact the shafts should besmooth. If there is a visible ridge at the edgeof where the rocker arm rides, the shaft isprobably worn excessively.

Cam followers and hydraulic tappets(M40 engines)21 Check the cam followers where theycontact the valve stems and pivot posts forwear, scoring and pitting. If there is excessivewear on both the followers and camshaft,then a new camshaft, complete with camfollowers, must be obtained.22 Similarly check the hydraulic tappets wherethey contact the bores in the cylinder head forwear, scoring and pitting. Occasionally, ahydraulic tappet may be noisy and requirerenewal, and this will have been noticed whenthe engine was running. It is not easy to check atappet for internal damage or wear once it hasbeen removed; if there is any doubt, a completeset of new tappets should be fitted.Camshaft23 Inspect the camshaft journals (the roundbearing areas) and lobes for scoring, pitting,flaking and excessive wear. Using amicrometer, measure the height of eachexhaust and intake lobe. Compare the heightsof all the exhaust lobes and intake lobes. If thereadings among the exhaust valve lobes orintake valve lobes vary more than about 0.08 mm, or if the camshaft is exhibiting anysigns of wear, renew the camshaft.24 Inspect the camshaft bearing surfaces inthe cylinder head for scoring and otherdamage. If the bearing surfaces are scored ordamaged, you’ll normally have to renew thecylinder head, since the bearings are simply amachined surface in the cylinder head. Note:A machine shop (particularly one thatspecialises in BMWs) or dealer servicedepartment may be able to provide analternative to fitting a new cylinder head, if theonly problem with the head is mildly-scoredcamshaft bearing surfaces.25 Using a micrometer, measure the journalson the camshaft, and record themeasurements (see illustration). Using atelescoping gauge or inside micrometer,

measure the camshaft bearing diameters in thecylinder head (on the M40 engine, refit thebearing caps first). Subtract the camshaftjournal measurement from its correspondingbearing inside diameter to obtain the oilclearance. Compare the oil clearance to what’slisted in this Chapter’s Specifications. If it’s notwithin tolerance, a new camshaft and/orcylinder head will be required. Note: Beforefitting a new cylinder head, check with amachine shop (particularly one that specialisesin BMWs). They may be able to repair the head.

10 Valves - servicing 41 Examine the valves as described in Sec-tion 9, paragraphs 13 and 14. Renew anyvalve that shows signs of wear or damage.2 If the valve appears satisfactory at thisstage, measure the valve stem diameter atseveral points using a micrometer (seeillustration 9.13). Any significant difference inthe readings obtained indicates wear of thevalve stem. Should any of these conditions beapparent, the valve(s) must be renewed.3 If the valves are in satisfactory condition theyshould be ground (lapped) into their respectiveseats to ensure a gas-tight seal. If the seat isonly lightly pitted, or if it has been re-cut, finegrinding compound should be used to producethe required finish. Coarse valve-grindingcompound should not normally be used,unless a seat is badly burned or deeply pitted.If this is the case, the cylinder head and valvesshould be inspected by an expert, to decidewhether seat re-cutting or even the renewal ofthe valve or seat insert is required.4 Valve grinding is carried out as follows.Place the cylinder head upside-down on abench, with a block of wood at each end togive clearance for the valve stems.5 Smear a trace of the appropriate grade ofvalve-grinding compound on the seat face,and press a suction grinding tool onto thevalve head. With a semi-rotary action, grindthe valve head to its seat, lifting the valveoccasionally to redistribute the grindingcompound (see illustration).

General engine overhaul procedures 2B•11

9.25 Measure each camshaft bearingjournal and its corresponding bearing

diameter in the cylinder head, then subtractthe journal diameter from the bearing

inside diameter to obtain the oil clearance

9.18 Look for signs of pitting, discolorationor excessive wear on the ends of therocker arms where they contact the

camshaft and the valve stem tip

10.5 Grinding-in a valve - do not grind-inthe valves any more than absolutely

necessary, or their seats will beprematurely sunk into the cylinder head

2B

9.16 Check each valve spring forsquareness

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6 If coarse grinding compound is being used,work only until a dull, matt even surface isproduced on both the valve seat and thevalve, then wipe off the used compound andrepeat the process with fine compound. Whena smooth, unbroken ring of light grey mattfinish is produced on both the valve and seat,the grinding operation is complete. Do notgrind in the valves any further than absolutelynecessary.7 When all the valves have been ground-in,carefully wash off all traces of grindingcompound using paraffin or a suitable solventbefore reassembly of the cylinder head.

11 Cylinder head - reassembly 51 Make sure the cylinder head is spotlessly-clean before beginning reassembly.2 If the head was sent out for valve servicing,the valves and related components willalready be in place. Begin the reassemblyprocedure with paragraph 8.3 Starting at one end of the head, apply

molybdenum disulphide (“moly”) grease orclean engine oil to each valve stem, and refitthe first valve.4 Lubricate the lip of the valve guide seal,carefully slide it over the tip of the valve, thenslide it all the way down the stem to the guide.Using a hammer and a deep socket or seal-fitting tool, gently tap the seal into place untilit’s completely seated on the guide (seeillustrations). Don’t twist or distort a sealduring fitting, or it won’t seal properly againstthe valve stem. Note: On some engines, theseals for intake and exhaust valves aredifferent - don’t mix them up.5 Drop the spring seat or shim(s) over thevalve guide, and set the valve spring andretainer in place.6 Compress the spring with a valve springcompressor and carefully refit the collets inthe upper groove, then slowly release thecompressor and make sure the collets seatproperly (see illustration).

7 Repeat paragraphs 3 to 6 for each of thevalves. Be sure to return the components totheir original locations - don’t mix them up!

M10, M20 and M30 engines8 Refit the rocker arms and shafts byreversing the dismantling sequence. Be sureto refit the rocker shafts in the correctorientation. The guide plate notches and thesmall oil holes face inwards; the large oil holesface down, toward the valve guides. 9 Lubricate the camshaft journals and lobes

(see illustration), then carefully insert it intothe cylinder head, rotating it as you go so thecamshaft lobes will clear the rocker arms. Itwill also be necessary to compress the rockerarms against the valve springs, as describedin Section 8, so they’ll clear the camshaftlobes. Be very careful not to scratch or gougethe camshaft bearing surfaces in the cylinderhead.

M40 engines10 Lubricate the bores for the hydraulictappets in the cylinder head, then insert thetappets in their original positions.11 Locate the thrust discs and cam followerson the valves and pivot posts in their originalpositions.12 Lubricate the bearing surfaces of thecamshaft in the cylinder head.13 Locate the camshaft in the cylinder headso that the valves of No 1 cylinder are bothopen, and the valves of No 4 cylinder are“rocking” (exhaust closing and inlet opening).No 1 cylinder is at the timing belt end. 14 Lubricate the bearing surfaces in thebearing caps, then locate them in their correctpositions and insert the retaining bolts.Progressively tighten the bolts to the specifiedtorque.15 Fit a new oil seal to the camshaft frontbearing cap (see Chapter 2A, Section 11).

All engines16 Refit the oil supply tube to the top of thecylinder head together with new seals, thentighten the bolts to the specified torque.17 The cylinder head may now be refitted(see Chapter 2A).

12 Pistons/connecting rods -removal 5

Note: Before removing the piston/connectingrod assemblies, remove the cylinder head andthe sump. On M10, M20 and M30 enginesonly, remove the oil pump. Refer to theappropriate Sections in Chapter 2A.1 Use your fingernail to feel if a ridge hasformed at the upper limit of ring travel (about 6 mm down from the top of each cylinder). If

2B•12 General engine overhaul procedures

11.9 Lubricate the camshaft bearingjournals and lobes with engine assemblypaste or molybdenum disulphide (“moly”)

grease

11.6 With the retainer fitted, compress thevalve spring and refit the collets as shown

11.4b . . .then lightly drive on the seal witha socket or piece of tubing

11.4a Lubricate the valve guide seal, andplace it on the guide (the valve should be

in place too) . . .

A light spring placed underthe valve head will greatlyease the valve grindingoperation.

Apply a small dab of grease to eachcollet to hold it in place, if necessary.

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carbon deposits or cylinder wear haveproduced ridges, they must be completelyremoved with a special tool called a ridgereamer (see illustration). Follow themanufacturer’s instructions provided with thetool. Failure to remove the ridges beforeattempting to remove the piston/connectingrod assemblies may result in piston ringbreakage.2 After the cylinder ridges have beenremoved, turn the engine upside-down so thecrankshaft is facing up.3 Before the connecting rods are removed,check the side play with feeler gauges. Slidethem between the first connecting rod andcrankshaft web until no play is apparent (seeillustration). The side play is equal to thethickness of the feeler gauge(s). If the sideplay exceeds the service limit, newconnecting rods will be required. If new rods(or a new crankshaft) are fitted, ensure thatsome side play is retained (if not, the rods willhave to be machined to restore it - consult amachine shop for advice if necessary). Repeatthe procedure for the remaining connectingrods.4 Check the connecting rods and caps foridentification marks. If they aren’t plainlymarked, use a small centre-punch to makethe appropriate number of indentations (seeillustration) on each rod and cap (1, 2, 3, etc.,depending on the cylinder they’re associatedwith).5 Loosen each of the connecting rod capnuts/bolts a half-turn at a time until they canbe removed by hand. Remove the No 1connecting rod cap and bearing shell. Don’tdrop the bearing shell out of the cap.6 Where applicable, slip a short length ofplastic or rubber hose over each connectingrod cap stud to protect the crankshaft journaland cylinder wall as the piston is removed(see illustration).7 Remove the bearing shell, and push theconnecting rod/piston assembly out throughthe top of the engine. Use a wooden hammerhandle to push on the upper bearing surfacein the connecting rod. If resistance is felt,double-check to make sure that all of theridge was removed from the cylinder.

8 Repeat the procedure for the remainingcylinders.9 After removal, reassemble the connectingrod caps and bearing shells in their respectiveconnecting rods, and refit the cap nuts/boltsfinger-tight. Leaving the old bearing shells inplace until reassembly will help prevent theconnecting big-end bearing surfaces frombeing accidentally nicked or gouged.10 Don’t separate the pistons from theconnecting rods (see Section 18).

13 Crankshaft - removal 5Note: The crankshaft can be removed onlyafter the engine has been removed from thevehicle. It’s assumed that the flywheel ordriveplate, vibration damper, timing chain orbelt, sump, oil pump and piston/connectingrod assemblies have already been removed.The rear main oil seal housing must beunbolted and separated from the block beforeproceeding with crankshaft removal.1 Before the crankshaft is removed, checkthe endfloat. Mount a dial indicator with thestem in line with the crankshaft and touchingthe nose of the crankshaft, or one of its webs(see illustration).2 Push the crankshaft all the way to the rear,

and zero the dial indicator. Next, prise thecrankshaft to the front as far as possible, andcheck the reading on the dial indicator. Thedistance that it moves is the endfloat. If it’sgreater than the maximum endfloat listed inthis Chapter’s Specifications, check thecrankshaft thrust surfaces for wear. If no wearis evident, new main bearings should correctthe endfloat.3 If a dial indicator isn’t available, feelergauges can be used. Identify the main bearingwith the thrust flanges either side of it - this isreferred to as the “thrust” main bearing (seeSection 24, paragraph 6). Gently prise or pushthe crankshaft all the way to the front of theengine. Slip feeler gauges between thecrankshaft and the front face of the thrustmain bearing to determine the clearance.4 Check the main bearing caps to see ifthey’re marked to indicate their locations.They should be numbered consecutively fromthe front of the engine to the rear. If theyaren’t, mark them with number-stamping diesor a centre-punch (see illustration). Mainbearing caps generally have a cast-in arrow,which points to the front of the engine.Loosen the main bearing cap bolts a quarter-turn at a time each, working from the outerends towards the centre, until they can beremoved by hand. Note if any stud bolts areused, and make sure they’re returned to theiroriginal locations when the crankshaft isrefitted.

General engine overhaul procedures 2B•13

12.4 Mark the big-end bearing caps inorder from the front of the engine to therear (one mark for the front cap, two for

the second one and so on)

12.3 Check the connecting rod side playwith a feeler gauge as shown

12.1 A ridge reamer is required to removethe ridge from the top of each cylinder - do

this before removing the pistons!

13.1 Checking crankshaft endfloat with adial indicator

12.6 To prevent damage to the crankshaftjournals and cylinder walls, slip sections of

rubber or plastic hose over the rod boltsbefore removing the pistons

2B

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5 Gently tap the caps with a soft-facedhammer, then separate them from the engineblock. If necessary, use the bolts as levers toremove the caps. Try not to drop the bearingshells if they come out with the caps.6 Carefully lift the crankshaft out of theengine. It may be a good idea to have anassistant available, since the crankshaft isquite heavy (see illustration). With thebearing shells in place in the engine block andmain bearing caps, return the caps to theirrespective locations on the engine block, andtighten the bolts finger-tight.

14 Intermediate shaft - removal and inspection 5

Note: The intermediate shaft is used on theM20 engine only. The shaft rotates in theengine block parallel to the crankshaft. It isdriven by the timing belt, and its only purposeis to drive the oil pump.1 Remove the timing belt (see Chapter 2A).2 With the belt removed, unbolt the gear fromthe intermediate shaft and unbolt the frontcover.3 Remove the oil pump driveshaft (seeChapter 2A).4 The shaft is held in the cylinder block by aretaining plate with two bolts. Remove thebolts, and pull the shaft forwards and out ofthe block.5 Look for any signs of abnormal wear on thebearing surfaces or the gear at the back endof the shaft, which drives the oil pump shaft. Ifthe bearing surfaces in the engine block showwear, they’ll have to be attended to by amachine shop.

15 Engine block - cleaning 2Caution: The core plugs may bedifficult or impossible to retrieveif they’re driven into the blockcoolant passages.

1 Remove the core plugs from the engineblock. To do this, knock one side of each pluginto the block with a hammer and punch,grasp the other side by its edge with largepliers, and pull it out.2 Using a gasket scraper, remove all traces ofgasket material from the engine block. Be verycareful not to nick or gouge the gasket sealingsurfaces.3 Remove the main bearing caps, andseparate the bearing shells from the caps andthe engine block. Tag the bearings, indicatingwhich cylinder they were removed from andwhether they were in the cap or the block,then set them aside.4 Remove all of the threaded oil gallery plugsfrom the block. The plugs are usually verytight - they may have to be drilled out and the

holes retapped. Use new plugs when theengine is reassembled.5 If the engine is extremely dirty, it should betaken to a machine shop to be steam-cleaned.6 After the block is returned, clean all oilholes and oil galleries one more time. Brushesspecifically designed for this purpose areavailable at most motor factors. Flush thepassages with warm water until the water runsclear, dry the block thoroughly, and wipe allmachined surfaces with a light, rust-preventive oil. If you have access tocompressed air, use it to speed the dryingprocess and to blow out all the oil holes andgalleries.

Warning: Wear eye protectionwhen using compressed air!

7 If the block isn’t extremely dirty or sludgedup, you can do an adequate cleaning job withhot soapy water and a stiff brush. Take plentyof time, and do a thorough job. Regardless ofthe cleaning method used, be sure to clean alloil holes and galleries very thoroughly, dry theblock completely, and coat all machinedsurfaces with light oil.8 The threaded holes in the block must beclean to ensure accurate torque readings

during reassembly. Run the proper-size tapinto each of the holes to remove rust,corrosion, thread sealant or sludge, and torestore damaged threads (see illustration). Ifpossible, use compressed air to clear theholes of debris produced by this operation. Besure also that the holes are dry - any oil orother fluid present could cause the block tobe cracked by hydraulic pressure when thebolts are tightened. Now is a good time toclean the threads on all bolts. Note that BMWrecommend that the cylinder head bolts andmain bearing bolts are renewed as a matter ofcourse.9 Refit the main bearing caps, and tighten thebolts finger-tight.10 After coating the sealing surfaces of thenew core plugs with a suitable sealant, refitthem in the engine block (see illustration).Make sure they’re driven in straight andseated properly, or leakage could result.Special tools are available for this purpose,but a large socket, with an outside diameterthat will just slip into the core plug, a 1/2-inchdrive extension, and a hammer, will work justas well.11 Apply non-hardening sealant to the newoil gallery plugs, and thread them into theholes in the block. Make sure they’retightened securely.12 If the engine isn’t going to bereassembled right away, cover it with a largeplastic bag to keep it clean.

2B•14 General engine overhaul procedures

15.10 A large socket on an extension canbe used to drive the new core plugs into

the block

15.8 All bolt holes in the block -particularly the main bearing cap and head

bolt holes - should be cleaned andrestored with a tap (be sure to removedebris from the holes after this is done)

13.6 Remove the crankshaft by liftingstraight up. Be very careful when removing

the crankshaft - it is very heavy

13.4 Use a centre-punch or number-stamping dies to mark the main bearingcaps to ensure refitting in their originallocations on the block (make the punch

marks near one of the bolt heads)

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16 Engine block - inspection 31 Before the block is inspected, it should becleaned (see Section 15).2 Visually check the block for cracks, rustand corrosion. Look for stripped threads inthe threaded holes. It’s also a good idea tohave the block checked for hidden cracks bya machine shop that has the specialequipment to do this type of work. If defectsare found, have the block repaired, if possible;otherwise, a new block will be required.3 Check the cylinder bores for scuffing andscoring.4 Measure the diameter of each cylinder atthe top (just under the wear ridge area), centreand bottom of the cylinder bore, parallel to thecrankshaft axis (see illustrations). 5 Next, measure each cylinder’s diameter atthe same three locations across thecrankshaft axis. Compare the results to thisChapter’s Specifications.6 If the required precision measuring toolsaren’t available, the piston-to-cylinderclearances can be obtained, though not quiteas accurately, using feeler gauges.7 To check the clearance, select a feelergauge, and slip it into the cylinder along withthe matching piston. The piston must bepositioned exactly as it normally would be.The feeler gauge must be between the pistonand cylinder on one of the thrust faces (90° tothe gudgeon pin bore).8 The piston should slip through the cylinder(with the feeler gauge in place) with moderatepressure.9 If it falls through or slides through easily, theclearance is excessive, and a new piston willbe required. If the piston binds at the lowerend of the cylinder and is loose toward thetop, the cylinder is tapered. If tight spots areencountered as the piston/feeler gauge isrotated in the cylinder, the cylinder is out-of-round.10 Repeat the procedure for the remainingpistons and cylinders.11 If the cylinder walls are badly scuffed or

scored, or if they’re out-of-round or taperedbeyond the limits given in this Chapter’sSpecifications, have the engine block reboredand honed at a machine shop. If a rebore isdone, oversize pistons and rings will berequired.12 If the cylinders are in reasonably goodcondition and not worn to the outside of thelimits, and if the piston-to-cylinder clearancescan be maintained properly, then they don’thave to be rebored. Honing (see Section 17)and a new set of piston rings is all that’snecessary.

17 Cylinder honing 31 Prior to engine reassembly, the cylinderbores must be honed so the new piston ringswill seat correctly and provide the bestpossible combustion chamber seal. Note: Ifyou don’t have the tools, or don’t want totackle the honing operation, most machineshops will do it for a reasonable fee.2 Before honing the cylinders, refit the mainbearing caps, and tighten the bolts to thetorque listed in this Chapter’s Specifications.3 Two types of cylinder hones are commonlyavailable - the flex hone or “bottle brush”

type, and the more traditional surfacing honewith spring-loaded stones. Both will do thejob, but for the less-experienced mechanic,the “bottle brush” hone will probably be easierto use. You’ll also need some paraffin orhoning oil, rags and an electric drill. Proceedas follows.4 Mount the hone in the drill, compress thestones, and slip it into the first cylinder (seeillustration). Be sure to wear safety gogglesor a face shield!5 Lubricate the cylinder with plenty of honingoil, turn on the drill, and move the hone up anddown in the cylinder at a pace that willproduce a fine crosshatch pattern on thecylinder walls. Ideally, the crosshatch linesshould intersect at approximately a 60° angle(see illustration). Be sure to use plenty oflubricant, and don’t take off any more materialthan is absolutely necessary to produce thedesired finish. Note: Piston ring manufacturersmay specify a smaller crosshatch angle thanthe traditional 60° - read and follow anyinstructions included with the new rings.6 Don’t withdraw the hone from the cylinderwhile it’s running. Instead, shut off the drilland continue moving the hone up and down inthe cylinder until it comes to a complete stop,then compress the stones and withdraw thehone. If you’re using a “bottle brush” typehone, stop the drill, then turn the chuck in thenormal direction of rotation while withdrawingthe hone from the cylinder.

General engine overhaul procedures 2B•15

16.4c The gauge is then measured with amicrometer to determine the bore size

16.4b The ability to “feel” when thetelescoping gauge is at the correct point

will be developed over time, so workslowly, and repeat the check until you’re

satisfied the bore measurement is accurate

16.4a Measure the diameter of eachcylinder just under the wear ridge (A), at

the centre (B) and at the bottom (C)

17.5 The cylinder hone should leave asmooth, crosshatch pattern, with the linesintersecting at approximately a 60° angle

17.4 A “bottle brush” hone will producebetter results if you’ve never honed

cylinders before

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7 Wipe the oil out of the cylinder, and repeatthe procedure for the remaining cylinders.8 After the honing job is complete, chamferthe top edges of the cylinder bores with asmall file, so the rings won’t catch when thepistons are refitted. Be very careful not to nickthe cylinder walls with the end of the file.9 The entire engine block must be washedagain very thoroughly with warm, soapywater, to remove all traces of the abrasive gritproduced during the honing operation. Note:The bores can be considered clean when alint-free white cloth - dampened with cleanengine oil - used to wipe them out doesn’tpick up any more honing residue, which willshow up as grey areas on the cloth. Be sure torun a brush through all oil holes and galleries,and flush them with running water.10 After rinsing, dry the block, and apply acoat of light rust-preventive oil to all machinedsurfaces. Wrap the block in a plastic bag tokeep it clean, and set it aside untilreassembly.

18 Pistons/connecting rods -inspection 3

1 Before the inspection process can becarried out, the piston/connecting rodassemblies must be cleaned and the originalpiston rings removed from the pistons. Note:Always use new piston rings when the engineis reassembled.2 Using a piston ring refitting tool, carefullyremove the rings from the pistons. Be carefulnot to nick or gouge the pistons in theprocess (see illustration).3 Scrape all traces of carbon from the top ofthe piston. A hand-held wire brush or a pieceof fine emery cloth can be used once themajority of the deposits have been scrapedaway. Do not, under any circumstances, use awire brush mounted in a drill motor to removedeposits from the pistons. The piston materialis soft, and may be damaged by the wirebrush.4 Use a piston ring groove cleaning tool toremove carbon deposits from the ringgrooves. Be very careful to remove only the

carbon deposits - don’t remove any metal,and do not nick or scratch the sides of thering grooves (see illustration).

5 Once the deposits have been removed,clean the piston/rod assemblies with solvent,and dry them with compressed air (ifavailable). Make sure the oil return holes in theback sides of the ring grooves are clear.6 If the pistons and cylinder walls aren’tdamaged or worn excessively, and if theengine block is not rebored, new pistonswon’t be necessary. Normal piston wearappears as even vertical wear on the pistonthrust surfaces (90° to the gudgeon pin bore),and slight looseness of the top ring in itsgroove. New piston rings, however, shouldalways be used when an engine is rebuilt.7 Carefully inspect each piston for cracksaround the skirt, at the pin bosses, and at thering lands.8 Look for scoring and scuffing on the thrustfaces of the skirt, holes in the piston crown,and burned areas at the edge of the crown. Ifthe skirt is scored or scuffed, the engine mayhave been suffering from overheating and/orabnormal combustion, which causedexcessively high operating temperatures. Thecooling and lubrication systems should bechecked thoroughly. A hole in the piston crownis an indication that abnormal combustion (pre-ignition) was occurring. Burned areas at theedge of the piston crown are usually evidenceof spark knock (detonation). If any of the above

problems exist, the causes must be corrected,or the damage will occur again. The causesmay include intake air leaks, incorrect fuel/airmixture, or incorrect ignition timing. On latervehicles with high levels of exhaust emissioncontrol, including catalytic converters, theproblem may be with the EGR (exhaust gasrecirculation) system, where applicable.9 Corrosion of the piston, in the form of smallpits, indicates that coolant is leaking into thecombustion chamber and/or the crankcase.Again, the cause must be corrected or theproblem may persist in the rebuilt engine.10 Measure the piston ring side clearance bylaying a new piston ring in each ring grooveand slipping a feeler gauge in beside it (seeillustration). Check the clearance at three orfour locations around each groove. Be sure touse the correct ring for each groove - they aredifferent. If the side clearance is greater thanthe figure listed in this Chapter’s Specifi-cations, new pistons will have to be used.11 Check the piston-to-bore clearance bymeasuring the bore (see Section 16) and thepiston diameter. Make sure the pistons andbores are correctly matched. Measure thepiston across the skirt, at 90° to, and in linewith, the gudgeon pin (see illustration). (Anydifference between these two measurementsindicates that the piston is no longer perfectlyround.) Subtract the piston diameter from thebore diameter to obtain the clearance. If it’sgreater than specified, the block will have tobe rebored, and new pistons and rings fitted.

2B•16 General engine overhaul procedures

18.11 Measure the piston diameter at a90-degree angle to the gudgeon pin, at the

same height as the gudgeon pin

18.10 Check the ring side clearance with afeeler gauge at several points around the

groove

18.4 The piston ring grooves can becleaned with a special tool, as shown

here

18.2 Removing the compression rings witha ring expander - note the mark (arrowed)

facing up

If a groove cleaning tool isn’t available,a piece broken off the old ring will dothe job, but protect your hands - pistonrings can be sharp

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12 Check the piston-to-rod clearance bytwisting the piston and rod in oppositedirections. Any noticeable play indicatesexcessive wear, which must be corrected. Thepiston/connecting rod assemblies should betaken to a machine shop for attention.13 If the pistons must be removed from theconnecting rods for any reason, they shouldbe taken to a machine shop. When this isdone, have the connecting rods checked forbend and twist, since most machine shopshave special equipment for this purpose.Note: Unless new pistons and/or connectingrods must be fitted, do not dismantle thepistons and connecting rods.14 Check the connecting rods for cracks andother damage. Temporarily remove the rodcaps, lift out the old bearing shells, wipe the rodand cap bearing surfaces clean, and inspectthem for nicks, gouges and scratches. Afterchecking the rods, fit new bearing shells, slip thecaps into place, and tighten the nuts finger-tight.

19 Crankshaft - inspection 31 Remove all burrs from the crankshaft oilholes with a stone, file or scraper (seeillustration).

2 Clean the crankshaft with solvent, and dry itwith compressed air (if available). Be sure toclean the oil holes with a stiff brush (seeillustration), and flush them with solvent.3 Check the main and connecting big-endbearing journals for uneven wear, scoring, pitsand cracks.4 Rub a copper coin across each journalseveral times (see illustration). If a journalpicks up copper from the coin, it’s too roughand must be reground.5 Check the rest of the crankshaft for cracksand other damage. If necessary, have amachine shop inspect the crankshaft.6 Using a micrometer, measure the diameterof the main and connecting rod journals, andcompare the results to this Chapter’s Specifi-cations (see illustration). By measuring thediameter at a number of points around eachjournal’s circumference, you’ll be able todetermine whether or not the journal is out-of-round. Take the measurement at each end ofthe journal, near the crank webs, to determineif the journal is tapered.7 If the crankshaft journals are damaged,tapered, out-of-round or worn beyond thelimits given in the Specifications, have thecrankshaft reground by a machine shop. Besure to use the correct-size bearing shells ifthe crankshaft is reconditioned.8 Check the oil seal journals at each end of

the crankshaft for wear and damage. If theseal has worn a groove in the journal, or if it’snicked or scratched (see illustration), thenew seal may leak when the engine isreassembled. In some cases, a machine shopmay be able to repair the journal by pressingon a thin sleeve. If repair isn’t feasible, a newor different crankshaft should be fitted.9 Examine the main and big-end bearingshells (see Section 20).

20 Main and connecting big-end bearings - inspection 3

1 Even though the main and connecting big-end bearings should be renewed during theengine overhaul, the old bearings should beretained for close examination, as they mayreveal valuable information about thecondition of the engine (see illustration).2 Bearing failure occurs because of lack oflubrication, the presence of dirt or otherforeign particles, overloading the engine, andcorrosion. Regardless of the cause of bearingfailure, it must be corrected before the engineis reassembled, to prevent it from happeningagain.

General engine overhaul procedures 2B•17

19.4 Rubbing a penny lengthways on eachjournal will reveal its condition - if copper

rubs off and is embedded in the crankshaft,the journals should be reground

19.2 Use a wire or stiff plastic bristlebrush to clean the oil passages in the

crankshaft

19.1 The oil holes should be chamfered sosharp edges don’t gouge or scratch the

new bearings

20.1 Typical bearing failures

A Scratched by dirt: debris embedded intobearing material

B Lack of oil: overlay wiped outC Improper seating: bright (polished) sectionsD Tapered journal: overlay gone from entire

surfaceE Radius rideF Fatigue failure: craters or pockets

19.8 If the seals have worn grooves in thecrankshaft journals, or if the seal contactsurfaces are nicked or scratched, the new

seals will leak

19.6 Measure the diameter of eachcrankshaft journal at several points to

detect taper and out-of-round conditions

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3 When examining the bearings, removethem from the engine block, the main bearingcaps, the connecting rods and the rod caps,and lay them out on a clean surface in thesame general position as their location in theengine. This will enable you to match anybearing problems with the correspondingcrankshaft journal.4 Dirt and other foreign particles get into theengine in a variety of ways. It may be left inthe engine during assembly, or it may passthrough filters or the crankcase ventilation(PCV) system. It may get into the oil, and fromthere into the bearings. Metal chips frommachining operations and normal engine wearare often present. Abrasives are sometimesleft in engine components after recondi-tioning, especially when parts are notthoroughly cleaned using the proper cleaningmethods. Whatever the source, these foreignobjects often end up embedded in the softbearing material, and are easily recognised.Large particles will not embed in the bearing,and will score or gouge the bearing andjournal. The best prevention for this cause ofbearing failure is to clean all parts thoroughly,and to keep everything spotlessly-cleanduring engine assembly. Frequent and regularengine oil and filter changes are alsorecommended.5 Lack of lubrication (or lubricationbreakdown) has a number of interrelatedcauses. Excessive heat (which thins the oil),overloading (which squeezes the oil from thebearing face) and oil “leakage” or “throw off”(from excessive bearing clearances, worn oilpump, or high engine speeds) all contribute tolubrication breakdown. Blocked oil passages,which usually are the result of misaligned oilholes in a bearing shell, will also oil-starve abearing and destroy it. When lack oflubrication is the cause of bearing failure, thebearing material is wiped or extruded from thesteel backing of the bearing. Temperaturesmay increase to the point where the steelbacking turns blue from overheating.6 Driving habits can have a definite effect onbearing life. Full-throttle, low-speed operation(labouring the engine) puts very high loads on

bearings, which tends to squeeze out the oilfilm. These loads cause the bearings to flex,which produces fine cracks in the bearingface (fatigue failure). Eventually, the bearingmaterial will loosen in places, and tear awayfrom the steel backing. Short-trip drivingleads to corrosion of bearings, becauseinsufficient engine heat is produced to driveoff the condensation and corrosive gases.These products collect in the engine oil,forming acid and sludge. As the oil is carriedto the engine bearings, the acid attacks andcorrodes the bearing material.7 Incorrect bearing refitting during engineassembly will lead to bearing failure as well.Tight-fitting bearings leave insufficient bearingoil clearance, and will result in oil starvation.Dirt or foreign particles trapped behind abearing shell result in high spots on thebearing, which will lead to failure.

21 Engine overhaul - reassembly sequence

1 Before beginning engine reassembly, makesure you have all the necessary new parts,gaskets and seals, as well as the followingitems on hand:

Common hand toolsA torque wrenchPiston ring refitting toolPiston ring compressorVibration damper refitting toolShort lengths of rubber or plastic hose to fitover connecting rod bolts (whereapplicable)PlastigageFeeler gaugesA fine-tooth fileNew engine oilEngine assembly oil or molybdenumdisulphide (“moly”) greaseGasket sealantThread-locking compound

2 In order to save time and avoid problems,engine reassembly should be done in thefollowing general order:

Piston ringsCrankshaft and main bearingsPiston/connecting rod assembliesOil pumpSumpCylinder head assemblyTiming belt or chain and tensioner assembliesWater pumpTiming belt or chain coversIntake and exhaust manifoldsValve coverEngine rear plateFlywheel/driveplate

22 Piston rings - refitting 21 Before fitting the new piston rings, the ringend gaps must be checked. It’s assumed thatthe piston ring side clearance has beenchecked and verified (see Section 18).2 Lay out the piston/connecting rodassemblies and the new ring sets, so that thering sets will be matched with the same pistonand cylinder during the end gap measurementand engine assembly.3 Insert the top ring into the first cylinder, andsquare it up with the cylinder walls by pushingit in with the top of the piston (see illustration).The ring should be near the bottom of thecylinder, at the lower limit of ring travel.4 To measure the end gap, slip feeler gaugesbetween the ends of the ring until a gauge equalto the gap width is found (see illustration). Thefeeler gauge should slide between the ring endswith a slight amount of drag. Compare themeasurement to this Chapter’s Specifications.If the gap is larger or smaller than specified,double-check to make sure you have thecorrect rings before proceeding.5 If the gap is too small, it must be enlarged,or the ring ends may come in contact witheach other during engine operation, whichcan cause serious damage to the engine. Theend gap can be increased by filing the ringends very carefully with a fine file. Mount the

2B•18 General engine overhaul procedures

22.5 If the end gap is too small, clamp afile in a vice, and file the ring ends (fromthe outside in only) to enlarge the gap

slightly

22.4 With the ring square in the cylinder,measure the end gap with a feeler gauge

22.3 When checking piston ring end gap,the ring must be square in the cylinder

bore (this is done by pushing the ring downwith the top of a piston as shown)

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file in a vice equipped with soft jaws, slip thering over the file, with the ends contacting thefile face, and slowly move the ring to removematerial from the ends. When performing thisoperation, file only from the outside in (seeillustration).6 Excess end gap isn’t critical unless it’sgreater than 1.0 mm. Again, double-check tomake sure you have the correct rings for yourengine.7 Repeat the procedure for each ring that willbe fitted in the first cylinder and for each ringin the remaining cylinders. Remember to keeprings, pistons and cylinders matched up.8 Once the ring end gaps have beenchecked/corrected, the rings can be fitted onthe pistons.9 The oil control ring (lowest one on thepiston) is usually fitted first. It’s normallycomposed of three separate components.Slip the spacer/expander into the groove (seeillustration). If an anti-rotation tang is used,make sure it’s inserted into the drilled hole inthe ring groove. Next, refit the lower side rail.Don’t use a piston ring refitting tool on the oilring side rails, as they may be damaged.Instead, place one end of the side rail into thegroove between the spacer/expander and thering land, hold it firmly in place, and slide afinger around the piston while pushing the railinto the groove (see illustration). Next, refitthe upper side rail in the same manner.10 After the three oil ring components havebeen fitted, check to make sure that both theupper and lower side rails can be turnedsmoothly in the ring groove.11 The middle ring is fitted next. It’s usuallystamped with a mark which must face up,towards the top of the piston. Note: Alwaysfollow the instructions printed on the ringpackage or box - different manufacturers mayrequire different approaches. Do not mix upthe top and middle rings, as they havedifferent cross-sections.12 Make sure the identification mark is facingthe top of the piston, then slip the ring into themiddle groove on the piston (see illus-tration 18.2). Don’t expand the ring any morethan necessary to slide it over the piston. Usea proper ring-fitting tool if available; with care,old feeler gauges can be used to prevent therings dropping into empty grooves.

13 Refit the top ring in the same manner.Make sure the mark is facing upwards. Becareful not to confuse the top and middlerings.14 Repeat the procedure for the remainingpistons and rings.

23 Intermediate shaft - refitting 51 Clean the intermediate shaft bearingsurfaces and the pressed-in bearing sleevesin the cylinder block.2 Lubricate the shaft, and slide it into theblock.3 Refit the two bolts that hold the retainingplate to the block.4 The remainder of the parts are fitted in thereverse order of removal.

24 Crankshaft - refitting andmain bearing oil clearancecheck

41 Crankshaft refitting is the first major step inengine reassembly. It’s assumed at this pointthat the engine block and crankshaft havebeen cleaned, inspected, and repaired orreconditioned.2 Position the block upside-down.3 Remove the main bearing cap bolts, and lift

out the caps. Lay them out in the proper orderto ensure correct refitting.4 If they’re still in place, remove the originalbearing shells from the block and the mainbearing caps. Wipe the bearing surfaces ofthe block and caps with a clean, lint-freecloth. They must be kept spotlessly-clean.

Main bearing oil clearancecheck5 Clean the back sides of the new mainbearing shells, and lay one in each mainbearing saddle in the block. If one of thebearing shells from each set has a largegroove in it, make sure the grooved shell isfitted in the block. Lay the other bearing fromeach set in the corresponding main bearingcap. Make sure the tab on the bearing shellfits into the recess in the block or cap.

Caution: The oil holes in theblock must line up with the oilholes in the bearing shell. Do nothammer the bearing into place,

and don’t nick or gouge the bearing faces.No lubrication should be used at this time.6 The flanged thrust bearing must be fitted inthe No 3 bearing cap and saddle in the M10engine, in the No 6 bearing cap and saddle inthe M20 engine (see illustration), in the No 4bearing cap and saddle in the M30 engine,and in the No 4 bearing saddle only in theM40 engine.7 Clean the faces of the bearings in the blockand the crankshaft main bearing journals witha clean, lint-free cloth.8 Check or clean the oil holes in thecrankshaft, as any dirt here can go only oneway - straight through the new bearings.9 Once you’re certain the crankshaft is clean,carefully lay it in position in the main bearings.10 Before the crankshaft can be permanentlyfitted, the main bearing oil clearance must bechecked.11 Cut several pieces of the appropriate-sizePlastigage (they must be slightly shorter thanthe width of the main bearings), and place onepiece on each crankshaft main bearingjournal, parallel with the crankshaft centreline(see illustration).12 Clean the faces of the bearings in thecaps, and refit the caps in their respective

General engine overhaul procedures 2B•19

22.9b DO NOT use a piston ring refittingtool when refitting the oil ring side rails

22.9a Refitting the spacer/expander in theoil control ring groove

24.11 Lay the Plastigage strips on themain bearing journals, parallel to the

crankshaft centreline

24.6 Refitting a thrust main bearing (notethe flanges) in the engine block bearing

saddle

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positions (don’t mix them up) with the arrowspointing towards the front of the engine. Don’tdisturb the Plastigage.13 Starting with the centre main bearing andworking out toward the ends, progressivelytighten the main bearing cap bolts to thetorque listed in this Chapter’s Specifications.On M10, M20 and M30 engines, tighten thebolts in three stages. On the M40 engine,tighten all the bolts initially to the Stage 1torque, then angle-tighten them by the anglegiven in the Specifications. Carry out theangle-tightening on each bolt in onecontrolled movement. Don’t rotate thecrankshaft at any time during the tighteningoperation.14 Remove the bolts and carefully lift off themain bearing caps. Keep them in order. Don’tdisturb the Plastigage or rotate thecrankshaft. If any of the main bearing caps aredifficult to remove, tap them gently from side-to-side with a soft-face hammer to loosenthem.15 Compare the width of the crushedPlastigage on each journal to the scale printedon the Plastigage envelope to obtain the mainbearing oil clearance (see illustration). Checkthe Specifications to make sure it’s correct.16 If the clearance is not as specified, the

bearing shells may be the wrong size (whichmeans different ones will be required). Beforedeciding that different shells are needed,make sure that no dirt or oil was between thebearing shells and the caps or block when theclearance was measured. If the Plastigagewas wider at one end than the other, thejournal may be tapered (see Section 19).17 Carefully scrape all traces of thePlastigage material off the main bearingjournals and/or the bearing faces. Use yourfingernail or the edge of a credit card - don’tnick or scratch the bearing faces.

Final crankshaft refitting18 Carefully lift the crankshaft out of theengine.19 Clean the bearing faces in the block, thenapply a thin, uniform layer of molybdenumdisulphide (“moly”) grease or engine oil toeach of the bearing surfaces. Be sure to coatthe thrust faces as well as the journal face ofthe thrust bearing.20 Make sure the crankshaft journals areclean, then lay the crankshaft back in place inthe block.21 Clean the faces of the bearings in thecaps, then apply engine oil to them.22 Refit the caps in their respectivepositions, with the arrows pointing towardsthe front of the engine.23 Refit the bolts finger-tight.24 Lightly tap the ends of the crankshaftforward and backward with a lead or brasshammer, to line up the main bearing andcrankshaft thrust surfaces.25 Tighten the bearing cap bolts to thespecified torque, working from the centreoutwards. On M10, M20 and M30 engines,tighten the bolts in three stages to the finaltorque, leaving out the thrust bearing capbolts at this stage. On M40 engines, tighten allof the bolts in the two stages given in theSpecifications.26 On M10, M20 and M30 engines, tightenthe thrust bearing cap bolts to the torquelisted in this Chapter’s Specifications.27 On manual transmission models, fit a newpilot bearing in the end of the crankshaft (seeChapter 8).

28 Rotate the crankshaft a number of timesby hand to check for any obvious binding.29 The final step is to check the crankshaftendfloat with a feeler gauge or a dial indicatoras described in Section 13. The endfloatshould be correct, providing the crankshaftthrust faces aren’t worn or damaged, and newbearings have been fitted.30 Fit the new seal, then bolt the housing tothe block (see Section 25).

25 Crankshaft rear oil seal -refitting 3

1 The crankshaft must be fitted first, and themain bearing caps bolted in place. The newseal should then be fitted in the retainer, andthe retainer bolted to the block.2 Before refitting the crankshaft, check theseal contact surface very carefully forscratches and nicks that could damage thenew seal lip and cause oil leaks. If thecrankshaft is damaged, the only alternative isa new or different crankshaft, unless amachine shop can suggest a means of repair.3 The old seal can be removed from thehousing with a hammer and punch by drivingit out from the back side (see illustration). Besure to note how far it’s recessed into thehousing bore before removing it; the new sealwill have to be recessed an equal amount. Bevery careful not to scratch or otherwisedamage the bore in the housing, or oil leakscould develop.4 Make sure the retainer is clean, then applya thin coat of engine oil to the outer edge ofthe new seal. The seal must be pressedsquarely into the housing bore, so hammeringit into place is not recommended. At the veryleast, use a block of wood as shown, or asection of large-diameter pipe (seeillustration). If you don’t have access to apress, sandwich the housing and sealbetween two smooth pieces of wood, andpress the seal into place with the jaws of alarge vice. The pieces of wood must be thickenough to distribute the force evenly aroundthe entire circumference of the seal. Work

2B•20 General engine overhaul procedures

25.5 Lubricate the lip of the seal, and boltthe retainer to the rear of the engine block

25.4 Drive the new seal into the retainerwith a wooden block or a section of pipe, if

you have one large enough - make surethe seal enters the retainer bore squarely

25.3 After removing the retainer from theblock, support it on two wooden blocks,

and drive out the old seal with a punch andhammer

24.15 Compare the width of the crushedPlastigage to the scale on the envelope todetermine the main bearing oil clearance

(always take the measurement at thewidest point of the Plastigage); be sure to

use the correct scale - standard andmetric ones are included

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slowly, and make sure the seal enters the boresquarely.5 The seal lips must be lubricated with multi-purpose grease or clean engine oil before theseal/retainer is slipped over the crankshaftand bolted to the block (see illustration). Usea new gasket - no sealant is required - andmake sure the dowel pins are in place beforerefitting the retainer.6 Tighten the retainer nuts/screws a little at atime until they’re all snug, then tighten them tothe torque listed in the Specifications inChapter 2A.

26 Pistons/connecting rods -refitting and big-end bearingoil clearance check

41 Before refitting the piston/connecting rodassemblies, the cylinder walls must beperfectly clean, the top edge of each cylindermust be chamfered, and the crankshaft mustbe in place.2 Remove the cap from the end of No 1connecting rod (refer to the marks madeduring removal). Remove the original bearingshells, and wipe the bearing surfaces of theconnecting rod and cap with a clean, lint-freecloth. They must be kept spotlessly-clean.

Connecting rod big-end bearingoil clearance check3 Clean the back side of the new upperbearing shell, then lay it in place in theconnecting rod. Make sure the tab on thebearing fits into the recess in the rod. Don’thammer the bearing shell into place, and bevery careful not to nick or gouge the bearingface. Don’t lubricate the bearing at this time.4 Clean the back side of the other bearingshell, and refit it in the rod cap. Again, makesure the tab on the bearing fits into the recessin the cap, and don’t apply any lubricant. It’scritically important that the mating surfaces ofthe bearing and connecting rod are perfectly

clean and oil-free when they’re assembled forthis check.5 Position the piston ring gaps so they’restaggered 120° from each other.6 Where applicable, slip a section of plasticor rubber hose over each connecting rod capbolt.7 Lubricate the piston and rings with cleanengine oil, and attach a piston ringcompressor to the piston. Leave the skirtprotruding about 6 or 7 mm to guide thepiston into the cylinder. The rings must becompressed until they’re flush with the piston.8 Rotate the crankshaft until the No 1connecting rod journal is at BDC (bottomdead centre). Apply a coat of engine oil to thecylinder walls.9 With the mark or notch on top of the pistonfacing the front of the engine, gently insert thepiston/connecting rod assembly into the No 1cylinder bore, and rest the bottom edge of thering compressor on the engine block.10 Tap the top edge of the ring compressorto make sure it’s contacting the block aroundits entire circumference.11 Gently tap on the top of the piston withthe end of a wooden hammer handle (seeillustration) while guiding the end of theconnecting rod into place on the crankshaftjournal. Work slowly, and if any resistance isfelt as the piston enters the cylinder, stopimmediately. Find out what’s catching, and fixit before proceeding. Do not, for any reason,force the piston into the cylinder - you mightbreak a ring and/or the piston.

12 Once the piston/connecting rod assemblyis fitted, the connecting rod big-end bearingoil clearance must be checked before the rodcap is permanently bolted in place.

13 Cut a piece of the appropriate-sizePlastigage slightly shorter than the width ofthe connecting rod big-end bearing, and lay it in place on the No 1 connecting rodjournal, parallel with the crankshaft centre-line.14 Clean the connecting rod cap bearingface, remove the protective hoses from theconnecting rod bolts, and refit the rod cap.Make sure the mating mark on the cap is onthe same side as the mark on the connectingrod.15 Refit the nuts/bolts, and tighten them tothe torque listed in this Chapter’s Specifica-tions. On M10 and M30 engines, work up tothe final torque in three stages. Note: Use athin-wall socket, to avoid erroneous torquereadings that can result if the socket iswedged between the rod cap and nut. If thesocket tends to wedge itself between the nutand the cap, lift up on it slightly until it nolonger contacts the cap. Do not rotate thecrankshaft at any time during this operation.16 Undo the nuts and remove the rod cap,being very careful not to disturb thePlastigage.17 Compare the width of the crushedPlastigage to the scale printed on thePlastigage envelope to obtain the oilclearance (see illustration). Compare it to theSpecifications to make sure the clearance iscorrect.18 If the clearance is not as specified, thebearing shells may be the wrong size (whichmeans different ones will be required). Beforedeciding that different shells are needed,make sure that no dirt or oil was between thebearing shells and the connecting rod or capwhen the clearance was measured. Also,recheck the journal diameter. If the Plastigagewas wider at one end than the other, thejournal may be tapered (see Section 19).

Final connecting rod refitting19 Carefully scrape all traces of thePlastigage material off the rod journal and/orbearing face. Be very careful not to scratch

General engine overhaul procedures 2B•21

26.17 Measuring the width of the crushed Plastigage todetermine the big-end bearing oil clearance (be sure to use the

correct scale - standard and metric ones are included)

26.11 Drive the piston gently into the cylinder bore with the end ofa wooden or plastic hammer handle

2B

The piston rings may try topop out of the ringcompressor just beforeentering the cylinder bore, so

keep some downward pressure on thering compressor

Page 22: Chapter 2 Part B: General engine overhaul procedures overhaul - general information . . . . . . . . . . . . . . . . . . . . . . . 2 Engine overhaul - reassembly sequence

the bearing - use your fingernail or the edge ofa credit card.20 Make sure the bearing faces are perfectlyclean, then apply a uniform layer ofmolybdenum disulphide (“moly”) grease orengine assembly oil to both of them. You’llhave to push the piston into the cylinder toexpose the face of the bearing shell in theconnecting rod - be sure to slip the protectivehoses over the rod bolts first, whereapplicable.21 Slide the connecting rod back into placeon the journal, and remove the protectivehoses from the rod cap bolts. Refit the rodcap, and tighten the nuts/bolts to thespecified torque.22 Repeat the entire procedure for theremaining pistons/connecting rods.23 The important points to remember are:a) Keep the back sides of the bearing shells

and the insides of the connecting rodsand caps perfectly clean whenassembling them.

b) Make sure you have the correctpiston/rod assembly for each cylinder.

c) The notch or mark on the piston mustface the front of the engine.

d) Lubricate the cylinder walls with clean oil.e) Lubricate the bearing faces when refitting

the rod caps after the oil clearance hasbeen checked.

24 After all the piston/connecting rodassemblies have been properly fitted, rotatethe crankshaft a number of times by hand tocheck for any obvious binding.

25 Check the connecting rod side play (seeSection 13).26 Compare the measured side play to theSpecifications to make sure it’s correct. If itwas correct before dismantling, and theoriginal crankshaft and rods were refitted, itshould still be right. If new rods or a newcrankshaft were fitted, the side play may beincorrect. If so, the rods will have to beremoved and taken to a machine shop forattention.

27 Initial start-up and running-in after overhaul 1

Warning: Have a fire extinguisherhandy when starting the enginefor the first time.

1 Once the engine has been refitted in thevehicle, double-check the engine oil andcoolant levels.2 With the spark plugs removed and theignition system disabled (see Section 3), crankthe engine until oil pressure registers on thegauge, or until the oil pressure warning lightgoes out.3 Refit the spark plugs, connect the HT leads,and restore the ignition system functions (seeSection 3).4 Start the engine. It may take a fewmoments for the fuel system to build up

pressure, but the engine should start withouta great deal of effort. Note: If backfiringoccurs through the throttle body orcarburettor, check the valve timing (check thatthe timing chain/belt has been correctly fitted),the firing order (check the fitted order of thespark plug HT leads), and the ignition timing.5 After the engine starts, it should be allowedto warm up to normal operating temperature.While the engine is warming up, make athorough check for fuel, oil and coolant leaks.6 Shut the engine off and recheck the engineoil and coolant levels.7 Drive the vehicle to an area with minimumtraffic, accelerate at full throttle from 30 to 50 mph, then lift off the throttle completely,and allow the vehicle to slow to 30 mph withthe throttle closed. Repeat the procedure 10 or 12 times. This will load the piston rings,and cause them to seat properly against thecylinder walls. Check again for oil and coolantleaks.8 Drive the vehicle gently for the first 500 miles (no sustained high speeds) andkeep a constant check on the oil level. It is notunusual for an engine to use oil during therunning-in period.9 At approximately 500 to 600 miles, changethe oil and filter.10 For the next few hundred miles, drive thevehicle normally - don’t nurse it, but don’tabuse it, either.11 After 2000 miles, change the oil and filteragain. The engine may now be considered tobe fully run-in.

2B•22 General engine overhaul procedures