0nan-- SENWI ( 9ULL2vinDIVISION OF ONAN CORPORATIONMINNEAPOLIS, MINNESOTA 55432

GENERAL TORQUE INFORMATION

When servicing Onan equipment be sure to torque alland studs according to recommendations contained inTwo factors to consider when discussing torque are :

1 . EXCESSIVE FRICTION2 . CLAMPING FORCE

nuts, bolts,this bulletin .

FRICTION is a force opposing motion . CLAMPING FORCE is a forcethat holds or fastens two or more things together .

NOTE : EXCESSIVE FRICTION CAN CAUSE DECREASING CLAMPING FORCE

Figure 1 shows a cap screw with excessive friction and no clamp-ing force . Figure 2 shows a cap screw with good clamping forcebecause of clean, lubricated threads .

TORQUE= 50 LB WITH NO CLAMPING FORCE

(T

EXCESSIVE FRICTION CAUSED BY :A. DIRTY MALE THREADSB. DIRTY FEMALE THREADSC. WARPED THREADSD. DRY THREADSE. CHIPS FROM TAPPINGF. WRONG SIZE OR CLASS OF THREADS

FIGURE 1 . POOR CLAMPING FORCE

1

TORQUE= 50 LB WITH GOOD CLAMPING FORCE

CLEAN .LUBRICATEDTHREADS

FIGURE 2 . GOOD CLAMPING FORCE

Eng .

7

TORQUE PROCEDURE1 . Clean all threads .2 . Lubricate threads with specified lubricant . (Assemble dry

if specified) .3 . Hand tighten all bolts .4 . Use the specified pattern (shown in Major Service Manual)

for tightening sequence .5 . Tighten bolts to 1/2 the torque value,6 . Repeat pattern bringing all bolts up to full torque value .

If no torque pattern is specified, start at centerline ofgasket and torque bolts as shown in Figure 3, followingnumbered sequence .

FIGURE 3 . BASIC TORQUE PATTERN

TABLE 1 . RECOMMENDED TORQUE IN FOOT-POUNDS

* NB Aluminum Rods 24-26 #, Forged Rods 27-29 #** CCK, CCKA and CCKB Forged Rods 27-29 #, Aluminum Rods 24-26 #

*** Zinc or Alum . Wheel 30-35, Cast Iron Wheel 40-45

Cylinder head bolts on "J" series water-cooled units that have beenoverhauled must be retorqued after Z/2 hour to 2 hours of operation .

(Not necessary on new units from factory .) Cylinder head bolts on "J" seriesair-cooled units must be retarqued to specified torque value after 50 hours ofoperation . (Back off Z/2 turn and then retighten .)

2

USE ENGINE LUBRICATING OIL AS A THREAD LUBRICANTDO NOT USE ANYLUBRICANT ONTHESE THREADS

ENGINESERIES

CYLINDERHEADS(COLD)

CONNECTINGRODS

REARBEARINGPLATE

FLYWHEELMOUNTINGSCREW

OILBASE

SPARKPLUGS

ARMATURETHRUSTUD

AJ,MAJ 24-26 10-12 20-25 35-40 25-30 25-30 25-30AK 24-26 10-12 20-25 35-40 25-30 25-30 25-30LK,LKB 29-31 26-28 20-25 35-40 25-30 25-30 35-40CCK,CCKB 29-31 * 20-25 35-40 43-48 25-30 35-40NB 29-31 * 30-35 ***30-35 38-43 15-20 35-40NH 22-25 27-29 25-27 ***30-35 18-23 15-20 35-40NHA,B,C 8-20 27-29 20-23 35-40 18-23 15-20 35-40BF 14-16 14-16 25-27 35-40 18-23 15-20 45-50CCKA 29-30 ** 20-25 35-40 43-38 25-30 35-40

W

TABLE 2. RECOMMENDED TORQUE IN FOOT-POUNDS

*

NOTE

:Us

e Ne

ver-

Seez

e in

Torqueing to this value

.

USEENGINE LUBRICATING OIL AS A THREAD LUBRICANT

DO NOT USE ANY LUBRICANT

ON

THESE THREADS

ENGINE

SERIES

CYL

.HEAD

(COLD)

CONN

.ROD

REAR

BRG

.PLATE

MAIN

BRG

;(4

CYL

.)

FLYWHEEL

TO

CRANKSHAFT

OIL

BASE

EXHAUST

MANIFOLD

(Tighten

Evenly)

INTAKE

MANIFOLD

DAMPER

FLYWHEEL

ASSY.

NUT

(4 CYL

.)

ROCKER

ARM STUD

IN

HEAD

ARMATURE THROUGH

STUD

SPAR

KPL

UGS

INJECTION

NOZZLE

REVOLVING

REVOLVING

ARM.

UNIT

SFIELD UNITS

JA

28-30

27-29

40-45

65-70

32-3

813

-15

13-15

25-30

30-4

025-30

JB

28-30

27-29

40-45

65-70

45-5

013

-15

13-15

25-3

055-60

25-3

0

JC

28-3

027-29

40-45

97-102

65-70

45-50

13-1

513-15

25-3

055

-60

25-3

0

MJA

44-4

627-29

40-45

65-70

32-3

813

-15

13-15

35-4

030

-40

25-30

MJB

44-4

627-29

40-45

65-70

45-50

13-15

13-1

535

-40

55-6

025

-30

MJC

44-4

627-29

40-45

97-102

65-70

45-50

13-15

13-1

517-21

35-4

055

-60

20-2

1

MDJA

44-4

627-29

40-45

65-70

32-38

13-15

13-15

35-4

030

-40

20-2

1

DJA

*44

-46

27-29

40-45

65-70

32-38

13-1

513

-15

35-4

030

-40

20-2

1

MDJB

44-4

627-29

40-45

65-7

045-50

13-1

513

-15

35-4

055

-60

20-2

1

DJB

*44

-46

27-29

40-45

65-70

45-50

13-1

513

-15

35-4

055

-60

20-2

1

MDSE

44-4

627-29

40-45

65-70

45-50

13-1

513

-15

35-4

055

-60

20-2

1

MDJC

44-4

627-29

40-45

97-102

65-70

45-50

13-1

513

-15

17-21

35-4

055

-60

20-2

1

DJC *

44-4

627-29

40-45

97-102

65-70

45-5

013

-15

13-1

517

-21

35-4

055

-60

20-2

1

MDJF

44-4

627-29

40-45

97-102

65-70

45-5

013

-15

13-1

517

-21

35-4

055

-60

-20-

21

RJC

44-4

627-29

40-45

97-102

65-70

45-50

13-1

513-15

17-2

135

-40

55-6

025

-30

RDJC

44-4

627-29

40-45

97-102

65-70

45-5

013

-15

13-15

17-2

135

-40

55-6

020

-21

RDJF

44-4

627-29

40-45

97-102

65-70

45-50

13-1

513-15

17-2

135

-40

55-60

20-21

SA

METRIC STANDARD

GRADE OF BOLT

MIN. TENSILE STRENGTH

GRADE MARKINGS

ON BEAD

METR

IC

NDARD

BOLT

U.S.

DIA

.

DEC.

EOUI

V.

6mm

.2362

14mm

.5512

22 mm

24mm

5D

8G

10K

12K

71,160

113,

800

114

2,20

0

170,679

P .S.

I.

P.S.

I.

P.S.

I.

P .S.

I.

In

14C

#

(D

V,

I

5 55

TORQUE

(IN FOOT POUNDS)

68mm

.3150

1016

10mm

.393

719

I31

12 mm

.4720

34

54 89

.945

261

419

8 22 40 70

.8661

182

284

i39

4

570

10

10 mm

2714 mm

4917mm

8619mm

464

SOCKET OR

WRENCH SIZE

ME

TRIC

BOLT

HEAD

NUT

10 m

m

14 mm

17 m

m

19 m

m

117

137

122mm

22mm

16mm

.6299

83

132

175

208

)24m

m24

mmi

18 mm

.709

111

182

!23

6

283

27 mm

27 m

m

32 mm 32 m

m

689

36mm 36mm

SPECIFICATIONS

FOR ALL BOLTS

SAE

SAE

182

5

MIN. TENSILE STRENGTH

64,000

105,

000

P.t1

.

;

P.S

I.

GRADE MARKINGS

ON HEAD

iU

.S.STANDARD

!iBOLT"_-_U

. S.

DIA.

DECEQUIV

114

.250

5

7

10'

10.5

3/8

17116

5/16

.3125

914

1330

00P51

SAE 6 19

TORQUE

U.S

.REGULAR

(IN

FOOT

POU

NDS)

BOLT

HEAD

NUT

22

34

37

9/16

518

55

60

5181 3/4

1/2

.500

37

601

85

92

3/4

13/16

9116

.562

5

53

88

120

132

.71

8

718

5/8

.625

74

120

167

180

15/16

3/4

.750

120

200

280

296

7/8

.875

190

302 ~ 440

7/16

4375

24

40

1.

1.000

282

25 466

660

714

1-1/

2

1.1/2

MULT

IPLY

REA

DING

S BY

12

FOR

INCH

POU

ND V

ALUES

SOCKET OR

WRENCH SIZE

1/2

1-1/

8

9/16 1. 1-1/

8

473

1-5/

16 1

-5/1

6

WHEN

USIN

GCH

ART

:1.

Use

FEL-PRO

C5A

comp

ound

or other high stress lubricant

under the bolt head as well as

on t

he t

hrea

ds. (Use torque-

figu

res

dire

ctly

.)2.

Inc

reas

e to

rque

by 2

0% i

fen

gine

oil

or

grea

se i

s us

edas lubricant

. (Don't torque

bolts dry.

)(F

ollo

w ma

nufa

c-tu

rers

spe

cifi

c sp

ecs

if a

vail

-able

.)3.

Red

uce

torq

ue b

y 20

% wh

ennew Cadmium

plat

ed b

olts

are

used

.

CAUT

ION

Bolt

s th

read

ed i

nto

alum

inum

may

requ

ire

much

les

s to

rque

.

Copyright P.

A. S

turt

evan

t Co

. 1965

Written Permission Given 2-19-69

114

WHITWORTH

TORQUE

WHITWORTH

U.S

IN FOOT POUNDS)

.

BOLT

7

9

10

3/8

.250

.375

9/16

'I.5

625

5/8

.625

3/4

718 1.

.750

.875

9 15 24 36 52 73 118

27 64 213

1

(3)

(4)RECOMMENDED SEQUENCE

FOR

TIGH

TENI

NG C

YLIN

DER

HEAD

BOL

TS(1) Tighten all bolts to 1/3 final

full

Tor

que .

(2)

Re-t

ight

en a

ll b

olts

to

2/3

fina

l To

rque

.Re

-tig

hten

all

bol

ts t

ofull

Torque and proper sequence

.Re

-tig

hten

to

full

Tor

que

agai

n in

rev

erse

seq

uenc

e.

(Thi

s in

sure

s th

at n

obolts

have

bee

n mi

ssed

.)Re-Torque to final specifica-

tion

s in

nor

mal

sequ

ence

agai

n af

ter

engi

ne w

arm

up.

(5)

15

18 31

43

51 259

21 287

HEAD

114

5/16

79

89

1/2

94

111

1128

*911

6-9

116

128

155

175

1-5/8

'518 7/8

Di-, on, glum on handles of U

. S.

w nc

hes

refe

r to

ado

aI s

,e o

f bo

lt h

ead

or n

or.

Dhne

nsio

n gl

uon

on W

hnwo

reh

ouch

es r

efer

to

the

hank

o.

body

dia

mete

r of

the

bolt

, NO

T TH

E BO

LT H

EAD

OR N

UT S

IZE

.

nan DIVI

DullDIVISION OF ONAN CORPORATION

MINNEAPOLIS, MINNESOTA 55432

ENGINE CRANKCASE OIL RECOMMENDATIONS FOR ONAN

LUBRICATING OIL SELECTION

EQUIPMENT

Lubricating oils for spark-ignited and diesel engines are made in a variety ofservice classifications, each in several viscosities . Selection of an oil fora particular engine, considering its fuel and operating conditions, is basedon these classifications .

OIL CLASSIFICATION

The classification of oil required depends on the kind of engine, the operatingconditions, and the fuel (gaseous fueled engines may require special ashcontent detergent oils) . A new system, jointly developed by the AmericanPetroleum Institute (API), the Society of Automotive Engineers (SAE), and theAmerican Society for Testing and Materials (ASTM) is now used to identify theclassifications . A new classification - SE - has been added to cover oils withvery high resistance to oil oxidation (or oil thickening) caused by high oiltemperatures .

VISCOSITY

Viscosity is a measurement of resistance to flow . For oil, this resistance isaffected by temperature . Multiple grade oils are made to provide startingcapability when the oil is cold and also to provide engine protection at operatingtemperatures . Viscosity identification is by SAE number . SAE 30 oil has aviscosity which is specified and measured at 210 € F . SAE lOW oil has a viscositywhich is specified and measured at 0 € F (the suffix W indicates a 0€ F specifica-tion) . Multigrade oils (such as 5W-30) must meet viscosity specifications atboth 0€ F and 210€ F .

RECOMMENDED CLASSIFICATIONS AND VISCOSITIES

The API/SAE/ASTM classifications and SAE viscosities for ONAN equipment aregiven in Table I . The new SE classification has not been mentioned in previousONAN publications . The oil recommendations listed herein for ONAN built enginessupersede those given in previous ONAN publications . For ashless - ashless dis-persant type oil or high ash oils, see Engine Manufacturer's Association (EMA)Form 1-12/70 (or later) columns "Natural Gas/LPG-Lo Ash" or "Natural Gas/LPG-Hi Ash" respectively and "Ash Content (Sulfated) % by Weight" . If natural gasengine oil is not available, use MIL-L-2104A (S-1) oils .

Eng

24

2-73

ENGINE

AJ, AK, BF, CCK

CCKA

CCKB

DEF, DEG, DEH

DFP, DFM, DFT,DFU, DFV, DFW

DJA, DJB, DJBA,DJC

DLA

DYA, DYB, DYC,DYD, DYG

EK, EM

FT

JB, JC

KB, KR

LK, LKB, MAJ,MCCK

MDEG, MDEH

gasoline-SE,SE/CCgaseousl/

CD, SE/CD

CC/CD, SE/CD,

CD, SE/CD

CD/SE, SE/CD

CC 3/

gasoline-SE,SE/CCgaseous - SD/CC

gasoline-SE ,SE/CCgaseous-

TABLE I - OIL RECONY"1ENDATIONS

SERV CLASS (by FUEL)

gasoline-SE, SE/CCgaseous 1/

gasoline-SE,SE/CCgaseous 1

CD/SE, CD/SDCC/SD -/, CC/SE ?/

gasoline-SE,SE/CCgaseous-SD/CC

gasoline1/1' E,SE/CCgaseous

CD,SE/CD

2

STARTING TEMP (F) AND VISCOSITY (SAE)

TEMP Below 0 0 00 to 32€ 32 0 to 900 Above 90VISC 5W-30 1OW-30, 30 50

5W-30

TEMP Below 0€ 00 to 32€ 32 € to 900 Above 90VISC 5W,5W-20 low 30 50

TEMP Below 0€ 00 to 32€ 32€ to 900 Above 90VISC 5W-30 lOW-30, 30 50

5W-30

TEMP Below -10€ -10€ to 40€ 40€ to 70€ 70€ to 100VISC 5W-30 low 20 30

TEMP -100 to 3~) 32€ to 90€ Above 90€VISC low 20 30

TEMP Below 0€ 00 to 320 Above 32€VISC 5W-20 or 5W-20, low, 30

5W-30 IOW-30 or5W-30

TEMP Below 32€ 32 € to 85 € Above 85€VISC low 20/20W 30

TEMP Below 00 00 to 320 Above 32€VISC low lOW-30, 30

5W-30

TEMP Below -100 -100 to 32€ 32 € to 100€ Above 100VISC 5W-30, 20 30 40

1OW-40

TEMP -10€ to 32 € 32 € to 90€ Above 900VISC low 20 30

TEMPVISC

Below 32 €5W-20 or

Above 32€30

5W-30

TEMPVISC

Below 32 €low

Above 32€30

TEMP Below -0€ 00 to 32 0 32€ to 900 Above 900VISC 5W-30 1OW-40, 30 50

5W-30

TEMP Below -10 0 -10€ to 400 40 € to 70€ 700 to 100VISC 5W-30 low 20 30

OIL OPERATING TEMPERATURE (F) AND VISCOSITY (SAE)

WA

any fuel -

TEMP

1300-1550

155€-1900

1900 -2300SE, SE/CC

VISC

20W

30

40

WB, WC

gasoline -SE,SE/CC

TEMP

140€-1600

160€-1800

180€ -2000

200€-220gaseous 4

VISC

20W

30

40

50

WE

gasoline-SE,SE/CC TEMP

130€-155€

155€-190€

190€ -230€gaseous

see page 1 VISC

20

30

40

WF, WK

4/

TEMP

1500-2000

200€ -230€VISC

30

40

1/ Ashless or low-ash detergent oils specifically made for gaseous-fueled engines are alsoapproved for LPG (butane, propane) or natural gas fuels .

21 CC oils are acceptable only for ambient temp . below 320 F or during break-in .

3/ Oil with 0 .03 to 0 .85 percent by weight sulfated ash .

4/ Oil made for gaseous-fueled engines and containing 5000 PPM of barium, calcium, orboth together with 0 .03 percent by weight zinc . Also has sulfated ash level of 2 .0 to3 .4 percent by weight . Lower ash oils may perform satisfactorily but high ash oilsimprove seat wear .

3

MDJA, MDJB, MDJC CD/SE,Cp/SD, TEMP Below 00 00 to 32 € Above 32 €MDJE, MDJF CC/SE 2 , CC/SD 2J VISC 5W-20 or 5W-20,

MJ C SE,SE/CC TEMP

5W-30

Below 32 €

1OW-30lOW,5W-30

Above 32€

30

VISC 5W-20 or 305W-30

NB, NH , NHA, gasoline -SE,SE/CC TEMP Below 0€ 0€ to 320 32€ to 90€ Above 90NHB NHC gaseous 1 VISC 5W-30 10W-40, 30 50

PC gasoline-SE,SE/CC TEMP Below 40€

5W-30

Above 40€gaseous-SD/CC VISC 5W-30 30

RDJC RDJF CD/SEACp/SD TEMP Below 0€ 0€ to 320 Above 32€2/CC/SE- , CC/SD VISC 5W-20 or 5W-20,

5W-30 10W-30,

RJC gasoline-SE,SE/CC TEMP Below 32€

1OW,SW-30

Above 32€

30

gaseous!/ VISC 5W-20 or 30

TD, TE, TF SE, SE/CC TEMP

5W-30

Below 32€ Above 32€VISC low 30

BASIS FOR RECOMMENDATIONS

The recommendations made in Table I are based upon knowledge required, the API/SAE/ASTMclassifications, and shop testing . The classifications define the best oil for eachoperating condition as described in Table II .

TABLE II

CLASSIFICATIONS AND OPERATING CONDITIONS

API/SAE/ASTMDESIGNATIONS

SERVICE AND OIL DESCRIPTIONS

UtilityGasolineEngineService Mildest operating conditions . Noperformance requirements . No additives except perhaps pour and/orfoam depressants .

MinimumDutyGasoline EngineService Conditions so mild that onlyminimum compounding is required . Oil has some resistance to oiloxidation and bearing corrosion - also some antiscuff qualities .

1964Gasoline EngineWarrantyService 1964 through 1967 automobilemanufacturer gasoline engine operating conditions . Oil designed tocontrol high and low temperature deposits, wear, and corrosion .

1968Gasoline EngineWarrantyService 1968 automobile manufacturersgasoline engine operating conditions . Performance better than thatof SC oils and may be used in their stead .

ASTMEngineTestSequence Oil designed to meet the 1972 require-ments of the automobile manufacturers and to stand up under highoperating temperatures caused by today's high speeds and heavy loads .Contains greater quantities of anti-oxidants which keep oil fromturning into molasses-like sludge . Safeguards against bearingfailure and total engine breakdown .

CA

DG

LightDutyDieselEngineService Oils intended for service in lightto moderate duty normally aspirated diesel engines using high qualitylow sulfur fuel . Meets MIL--L-2104A (1954)

CB DG ModerateDutyDieselEngineService These oils are similar to CAoils except that they are capable of providing the protection whenhigh sulfur fuels are used .

CC

DM

ModerateDutyDieselandGasoline EngineService Oils meeting re-quirements of MIL-L-2104B (1964) . Provides low temperature anti-sludgeand anti-rust performance in lightly supercharged diesel engines .

CD

DS

SevereDutyDieselEngineService These oils are for service typical(Series 3)

of supercharged diesel engines in high speed, high output duty re-quiring very effective wear/deposit control . Provide protection versusbearing corrosion and high temperature deposit formation in superchargeddiesel units using wide quality range fuels, CD oils meet the Cater-pillar Tractor Co . Series 3 Specification .

4

NEW OLD

SA ML

SB MM

SC 1964-1967 MS

SD 1968-1971 MS

SE

nanPrinted in U S A

12NI

91jL1271fl ENGDIVISION OF ONAN CORPORATION

MINNEAPOLIS, MINNESOTA 5543250

2-75

GASOLINE FUEL

LEADED VS NONLEADED

Most gasoline contains some lead additives (Tetraethyl lead) which accumulatein engine combustion chambers .

Since generator sets operate at constant (governor-controlled) speeds, it isdifficult for the engine to "blow out" these lead deposits through the exhaustports as is possible with engines operating at variable speeds . Thereforeconstant speed engines may require more frequent removal of deposits and moremaintenance .

For this reason, Onan recommends the use of low-lead and nonleaded gasoline .Onan has run several conclusive tests with leaded vs nonleaded gasoline onvarious governor controlled engines . We find that using nonleaded gasolinehelps reduce problems such as :

Cylinder Head Deposits (low power)Sticking Valves or Burned ValvesSpark Plug FoulingPiston WearRing Wear and StickingCylinder Wall Wear, etc .Poor Oil Control After Ring Fouling

For new Onan engines, we recommend using nonleaded gasoline from the start .On older engines, if you desire to change from leaded gasoline to nonleaded,the engine head must be taken off and all lead deposits removed from theengine .

If Zead deposits are not removed from the engine beforeswitching from leaded to nonleaded gasoline, preignition

could occur causing severe damage to the engine .

NOTE : The information in this bulletin on the use of lead free or lowlead gasoline pertains to Onan-built engines ONLY . For Onan generatorsets of all sizes having Ford, International, Waukesha, Tecumseh, orBriggs and Stratton engines, consult the engine manufacturers owner'smanual accompanying the unit for specific fuel recommendations . Thisis a separate manual from the Onan Operator's manual which also comeswith each unit .

0nanPr nted in U . S . A

121vit gullDIVISION OF ONAN CORPORATION

MINNEAPOLIS, MINNESOTA 55432

ONAN TWO-CYLINDER OPPOSED ENGINE FIRING ON ONE CYLINDER

ONAN two-cylinder opposed engines (BF-CCK-NH) will run fairly well when firing on 1cylinder, if no load or a minimum load isapplied . However, loss of power is quicklynoticed when a full load is put on theengine . If this should occur, check thefollowing in this order :

1 . Fuel Flow2 . Ignition3 . Compression

FUEL FLOW

A lean fuel mixture is the major cause of a two-cylinder opposed enginefiring on only 1 cylinder . A lean mixture usually results from an im-properly adjusted main fuel adjustment screw on the carburetor .

With the engine running, gradually turn the main fuel adjustment screwcounterclockwise until the cylinder begins to fire .

If, after twocomplete turns, the cylinder fails to fire, return the adjustment screwto its original position .

Check the intake manifold and connections for leaks . If uncertain, applyoil to the manifold gaskets (without disassembling) while the unit isrunning . Subsequent smoking or an increase in RPM indicates a leak . Repairor replace as required .

IGNITION

Check the ignition system even if the spark plugs seem to be working :

€

Check the breaker points for correct gap .€

Check for a sticking breaker plunger . _Check spark plugs for fouling, cracked insulation and the correct gap .

1

Eng58

2/75

€ Check spark plug wires for loose connections and possible shorts .€

Check the coil for continuity and shorts . Test the primary and second-ary windings as follows :

1 . Use a volt/ohm/ammeter or equivalent .2 . Place black lead on ground(-) terminal of coil and red lead to positive

(+) terminal . Primary resistance should read 0 .50 to 4 .73 ohms .3 . Change resistance setting on meter . Place meter leads inside of

spark plug cable holes (Figure 1) . Secondary resistance should read10,800 to 15,400 ohms .

FIGURE 1 . TESTING IGNITION COIL

COMPRESSION

Low compression can also cause a "dead" cylinder . Any one of the followingwill lower compression . Check and repair or replace as necessary :

1 . Incorrect valve clearance .2 . Broken valve spring .3 . Warped or burned valve and/or valve seats .4 . Worn or broken piston rings .5 . Blown head gasket .

2