RENR8121-00

30Page,EAR

RENR8121

October 2004

789C Off-Highway Truck

Hydraulic System

2BW659-UP

©2004 Caterpillar

All Rights Reserved

Printed in U.S.A.

Description Media Number

Specifications SENR1521

Systems Operation SENR1522

Testing and Adjusting SENR1523

Disassembly and Assembly SENR1524

Specifications: (Hydraulic System) SENR1531

Testing and Adjusting: (Hydraulic System) SENR1532

Specifications: (Steering System) SENR1525

Testing & Adjusting: (Steering System) SENR1526

Specifications: (Air System & Brakes) SENR1527

Testing & Adjusting: (Air System & Brakes) SENR1528

Specifications, System Operation, Testing &

Adjusting: (Oil Evacuation System)RENR2223

Specifications: (Suspension Cylinder) SENR1529

Schematic (Electrical System) SENR1535

Automatic Electronic Traction Aid (AETA) SENR2986

Additional Manuals

Related Manuals

Power Train

Machine Systems

Electrical System:

Tap

NumberDescription

Schematic

Location

Machine

Location

A Low Steering Pump Pressure I - 15 41

B High Steering Pressure (Accumulator) H - 13 23

C Hoist Pump Pressure (Front) G - 5 63

D Hoist Pump Pressure (Rear) G - 5 63

E Left Rear Brake Cooling Pressure J - 10 1

F Left Rear Parking Brake Pressure I - 10 32

G Right Rear Parking Brake Pressure C - 10 32

H Rear Service Brake Pressure F - 11 32

J Front Service Brake Pressure F - 3 35

K Torque Converter Charge Pump Pressure I - 6 64

L Torque Converter Lock-up Clutch Pressure I - 5 10

M Torque Converter Outlet Pressure I - 4 24

N Transmission Lube Pump Pressure E - 15 43

O Left Brake Pressure Test Port F - 10 2

P Transmission Charge Pump Pressure E - 16 37

Q Right Brake Pressure Test Port E - 10 2

R Hoist System Power Unit (Auxiliary) C - 9 38

S Steering System Power Unit (Auxiliary) G - 15 36

X Transmission System Oil (Sampling) D - 15 57

Y Hoist and Torque Converter System Oil (Sampling) H - 7 19

Z Streeting System Oil (Sampling) I - 16 36

Tap Locations

Pressure, Sampling, and Sensor

Machine

Location

Schematic

LocationDescription

Part

Number

1 B - 11,J - 11 Service and Parking Brake (Rear) 5T-4489

2 F - 9 Traction Control Valve 9G-9208

3 B - 8 Hoist Cylinders 9T-2807

4 F - 9 Check Valve (Electric Drive Pump) 9T-3086

5 E - 10 Electric Drive Pump (Parking and Secondary Brake Release) 5T-1060

6 I - 9 Brake Valve (Parking and Secondary) 149-4133

7 J - 9 Orifice 122-7765

8 J - 9 Screen 6E-5065

9 H - 9 Check Valve 138-4733

10 I - 5 Lockup Clutch and Synchronizing Valve (Torque Converter) 8E-6146

11 D - 2,I - 2 Service and Parking Brake (Front) 5T-5070

18 J - 9 Makeup Tank for Service Brake Oil 6E-1851

19 H - 7 Hydraulic Filter (Parking Brake Release) 6P-4603

20 B - 3,C - 3 Bypass Switch (5) 9X-7781

21 J - 4 Diverter Valve (Torque Converter and Front Brake Cooling) 105-0170

24 I - 5 Relief Valve (Torque Converter Outlet) 9W-7403

26 G - 11 Air Over Hydraulic Cylinder (Brake) 8W-3405

27 J - 5 Screen (Torque Converter and Front Brake Cooling) 6E-1349

28 J - 3 Oil Cooler (Front Brake Cooling) 141-4108

29 E - 3 Orifice 8W-4042

32 F - 11 Slack Adjuster (Rear) 5T-7670

33 B - 10 Oil Cooler (Rear Brake Cooling) 141-4108

34 B - 10 Screen 6E-6640

35 F - 2 Slack Adjuster (Front) 2G-5900

38 D - 8 Control Valve 132-2048

39 B - 7 Counterbalance Valve (Hoist) 132-7102

40 F - 4 Pump Drive 2A-6516

41 G - 14 Piston Pump (Steering) 6E-5650

45 C - 3,D - 3 Hoist Screens 6E-5471

48 G - 7 Rear Brake Cooling Pump Section 3E-3882

49 H - 6 Parking Brake Release Pump Selection 6T-6147

50 H - 6 Torque Converter Charging Pump Section 6T-6147

51 H - 6 Torque Converter Scavenge Pump Section 6T-6147

52 E - 7 Hydraulic Tank (Torque Converter, Hoist, Brake and Transmission) 161-0536

53 E - 6 Suction Screens 9T-3850

58 H - 4 Air Breather (Hoist, Torque Converter and Brake) 8X-4575

61 B - 11,I - 11 Service and Parking Brake (Rear) 5T-4489

62 J - 6 Relief Valve (Torque Converter Inlet) 3P--0348

63 G - 5 Hoist and Rear Brake Cooling Gear Pump 139-2454

64 I - 6 Hydraulic Filter (Torque Converter) 4T4760

66 D - 2,I - 2 Service and Parking Brake (Front) 5T-5070

73 H - 5 Torque Converter 116-5811

80 D - 9 HARC Valve 177-8840

80 E - 9 Check Valve 9T-6173

81 D - 10 Accumulator Grp. 241-3147

12 I - 15 Pressure Switch (Steering Pump Oil Low) 3E-7809

13 I - 15 Orifice 8X-7851

14 G - 13 Metering Pump (Steering) 9T-1318

22 J - 13 Steering Cylinders 4T-6797

23 I - 13 Steering Control Valve 9T-1318

30 I - 17 Accumulator Charging Valve 148-9237

36 J - 16 Solenoid and Relief Valve (Steering) 6E-3965

41 H - 15 Piston Pump (Steering) and Pressure Compensator Valve 6E-5656

42 I - 15 Orifice 1T-0936

46 J - 17 Pressure Switch (Steering Pump Oil High) 3E-6461

47 J - 16 Steering Accumulators 6E-6611

60 G - 16 Filter (Steering Pump Case Drain) 4T-4284

67 G - 16 Steering Tank 155-6660

68 G - 17 Steering Tank Filter 9J-5461

69 H - 17 Brake Relief Valve 9T-0818

70 J - 16 Check Valve (Steering) 9T-2553

20 D - 16 Bypass Switch 9X-7781

37 E - 14 Magnetic Screen (Transmission) 7T-4554

40 C - 15 Pump Drive 2A-6516

43 E - 16 Oil Cooler (Transmission) 4W-5056

44 D - 15 Relief Valve (Transmission Cooler Inlet) 2P-2859

52 B - 14 Hydraulic Tank (Torque Converter, Hoist, Brake and Transmission) 161-0536

53 B - 16 Suction Screen 9T-3850

54 C - 15 Transmission Charging Pump Section 156-8525

55 C - 15 Transmission Planetary 156-8525

56 C - 15 Transmission Scavenge Pump Section 156-8525

57 D - 16 Hydraulic Filter (Transmission Charging) 6P-4603

59 E - 13 Air Breather (Transmission) 6G-0078

65 D - 15 Hydraulic Filter (Transmission Lubrication) 6P-4603

Component Locations

Steering Hydraulic System

Transmission Hydraulic System

B

CD

G

F

HJ

K

L

M

N

Q

PSZ

X

Y

L

E

E

F

G

H

O Q

E

E

16

Hydraulic Symbols (Electrical)

Electrical Symbols Table

325-AG135 PK-14

Circuit IdentificationNumber

Wire Color Wire Gauge

Harness identification code

This example indicates

wire 135 in harness "AG".

325-PK-14

Wire Gauge

Wire Color

Circuit Number

Identification

Wire Number Identification Codes

Current Standard

Previous Standard

Electrical Schematic Example Hydraulic Schematic Example

325-PK

Wire ColorCircuit Number

Identification

B A

Wire

Wire

(EXAMPLE VALVE)

Current Standard

Transducer(Fluid)

Transducer(Gas / Air)

G

Generator

Electrical WirePressure Switch

MElectric Motor

Pressure Switch

(Adjustable)

Temperature Switch

T

PressureSymbol

TemperatureSymbol

LevelSymbol

FlowSymbol

Electrical Symbols (Electrical)

ONE POSITION TWO POSITION THREE POSITION

VENTEDPRESSURIZED RETURN ABOVE FLUID LEVEL RETURN BELOW FLUID LEVEL

LINES CROSSING LINES JOINING

TWO-WAY THREE-WAY FOUR-WAY

SPRINGCONTROL VALVES RESTRICTION LINE RESTRICTION

(FIXED)

2-SECTION PUMP

MAIN AUX.

SPRING

(ADJUSTABLE)

VARIABILITY LINE RESTRICTION

(VARIABLE)

LINE RESTRICTIONVARIABLE and PRESSURE

COMPENSATED

PRESSURE

COMPENSATION

PUMP: VARIABLE and

PRESSURE COMPENSATED

ENERGY TRIANGLES

HYDRAULIC PNEUMATIC

MEASUREMENT

PRESSURE TEMPERATURE FLOW

ROTATING SHAFTS

UNIDIRECTIONAL BIDIRECTIONAL

PUSH-PULL LEVER PEDALGENERAL MANUAL PUSH BUTTON SPRING

MANUAL CONTROL SYMBOLS

HYDRAULIC MOTORS

FIXED

DISPLACEMENT

VARIABLE DISPLACEMENT

NON-COMPENSATED

UNIDIRECTIONAL

BIDIRECTIONAL

HYDRAULIC PUMPS

FLUID STORAGE RESERVOIRS

CROSSING AND JOINING LINES

VALVE ENVELOPES VALVE PORTS

BASIC COMPONENT SYMBOLS

FLUID CONDITIONERPUMP or MOTOR

FLUID POWER SYMBOLS

FIXEDDISPLACEMENT

VARIABLE DISPLACEMENT

NON-COMPENSATED

UNIDIRECTIONAL

BIDIRECTIONAL

VALVES

PILOT CONTROL SYMBOLSRELEASED PRESSURE

EXTERNAL RETURN INTERNAL RETURN

REMOTE SUPPLY PRESSURE

SIMPLIFIED COMPLETE INTERNAL

SUPPLY PRESSURE

ACCUMULATORS

SPRING LOADED GAS CHARGED

SOLENOID

or MANUALSOLENOID

and PILOT

SOLENOID and

PILOT or MANUAL

COMBINATION CONTROLS

SOLENOIDSERVO THERMAL DETENT

HYDRAULIC AND PNEUMATIC CYLINDERS

DOUBLE ACTINGSINGLE ACTING

BASIC SYMBOL SPRING LOADED

CHECK VALVES

TWO

POSITION

INFINITE

POSITIONING

FLOW IN ONE

DIRECTION

FLOW ALLOWED IN

EITHER DIRECTION

THREE

POSITION

CROSS

FLOWPARALLEL

FLOW

INTERNAL PASSAGEWAYS

NORMAL POSITION

A B

P T

A B

P T

SHIFTED POSITION INFINITE POSITION

CONTROL VALVES

ATTACHMENT

MANUAL SHUTOFF

(12) Steering piston pump(16) Pressure compensator valve(17) Pump drive(A) Low steering pump pressure test port.(1) Low pressure switch from steering piston pump

(5) Steering solenoid and relief valve(6) Steering check valve(18) Steering relief valve(19) Steering solenoid valve(Z) Steering system oil sampling port(S) Steering system Power Unit (Auxiliary)

(8) Steering pump case drain filter(9) Steering filter(10) Steering hydraulic tank(13) Breaker relief valve

(B) High steering pressure test port.

Top view of Rear Brake Lines

(E) Left Rear Brake Cooling Pressure

(N) Pressure Tap for Transmission Lube Pump.

(J) Pressure Tap for Front Service Brake

(H) Pressure Tap for Rear Service Brake. (O) Left Brake Pressure Test Port(Q) Right Brake Pressure Test Port.

5

N

Z

1

1

1 2 3

LM

1

2 6 7

3

45

6

23

2

P

1

2 3

Y

D

C

B

E

H

G

F

J

S

1

4

2

3

K

H

O Q

2

3

456

1

11

10

40

3

14

18

1920

20

21

22

23

24

27

22

28

2930

HH

32

33

35

36

37

384143

45

20

46

48

53 52

54

5758

60

61

62

6465

7059

66

67

6312

47

26

20

80(1)Torque converter outlet relief valve.(M)Pressure tap for torque converter outlet pressure.(2) Torque converter inlet relief valve.(L) Pressure tap for lockup clutch pilot oil.

(1) Torque converter, hoist, brake, and transmission hydraulic tank(2) Torque converter, hoist, and brake section(3) Transmission section

(1) Pump drive(2) Hoist and rear brake cooling gear pump (front section)(3) Hoist and rear brake cooling gear pump (rear section)(4) Inlet from the hydraulic tank(5) Inlet from the hydraulic tank(6) Outlet to the hoist control valve(7) Outlet to the hoist control valve

(Y) Parking Brake Filter Oil (Sampling)(6) Parking brake release hydraulic filter(23) Bypass switch(16) Torque converter and front brake cooling screen

(P) Pressure tap for the transmission charging section

(1) Torque converter and front brake cooling oil cooler(5) Torque converter and front brake cooling diverter valve

(2) Rear brake oil coolers(3) Screens for the rear brake oil coolers

(H) Pressure tap for Rear Service Brake(F) Pressure tap for Left parking brake release pressure(G) Pressure tap for Right parking brake release pressure

(1) Torque converter hydraulic filter(2) Inlet line(3) Outlet line(4) Bypass switch(K) Torque Converter Charge pump pressure

16

12

17

A

19

5

18

6

1013

8

9

73

5556

51

49

50

68 69

13

34

44

42

7

89

39

81

A

O

R

1460 67 68

2829

21

56 59

10

24 626

1227 19

20

22

11

4647

23

36

70

3066

43 33

44

64

63

4041

57 65

53 52

4849

505156

54

35

54

18

26

26

38 39

45

20

2

70 71 55

8037

32

611

72

72

A

K

B

C D J

MNZ

P

RS Y

X

Side view of steering oil lines

(1) Steering accumulators(2) Pressure switch for high pressuroil from the steering piston pump

(4) Steering cylinders(7) Steering control valve(8) Steering pump case drain filter(10) Steering hydraulic tank

(12) Steering piston pump(14) Pressure switch for low pressure

oil from the steering piston pump(15) Orifice(16) Pressure compensator valve(AA) Pressure tap for low pressure oil

from the steering piston pump

Top view of steering oil lines

(1) Steering accumulators(2) Pressure switch for high pressuroil from the steering piston pump

(3) Accumulator charging valve(4) Steering cylinders(5) Steering solenoid and relief valve

(7) Steering control valve(8) Steering pump case drain filter(10) Steering hydraulic tank(12) Steering piston pump(14) Pressure switch for low pressure

oil from the steering piston pump

RENR8121-00

30Page,Color2,DGM

LINE PATTERNS

Drain / Return Lines

Component Group

Pilot / Load Sensing Pressure

Pressure Line

Attachment

Air Line

CALLOUTS

Taps (Pressure, Sampling,Sensor) by letter

Components by number

YY

52

HYDRAULIC CIRCUIT COLOR DESCRIPTIONS

Hoist and Rear Brake Cooling Pump Circuit

Primary and Secondary Parking Brake Pump Circuit

Steering Pump Circuit

Transmission Pump Circuit

Supply Line.

Drain / Return Line.

Service and Parking Brake Circuit

Steering Cylinder Circuit

Torque Converter Charge Pump Circuit

Hoist Cylinder Circuit

Torque Converter Relief Circuit

Brake Cooling

Parking Brake

Release Hydraulic

Filter 6P-4603

Auxiliary PowerUnit Port

Metering Pump

(Steering) 9T-1318

SteeringControl Valve9T-1317

Screen

6E-6640

Hydraulic ARCValve 177-8840

Bypass Switch

116-9933

Bypass Switch

9X-7781Torque Converter

Hydraulic Filter

9T-3838

Relief Valve3P-0348

Torque Converter

Lockup Valve

8E-6146

Oil Cooler

(Front Brake Cooling)

141-4108

Torque Converter and

Front Brake Cooling

Diverter Valve 105-0170

Torque Converter

116-5811

Shuttle Valve8J-6173

Air Over HydraulicCylinder 8W-3405

High Pressure

Screen 6E-1349

Pressure Switch

(Steering Pump Oil High)

3E-6461

Steering

Accumulators

6E-6611

Check Valve (Steering)

9T-2553

Solenoid and Relief Valve(Steering) 6E-6298

AccumulaterCharging Valve148-9237

Pressure Switch(Steering Pump Oil Low)3E-7809

Orifice

8X-7851

Orifice

1T-0936

Filter (Steering Pump Case Drain)

4T-4284

Steering Cylinders

4T-6797

Piston Pump (Steering) andPressure Compensator Valve6E-5656

Transmission Planetary

Transmission Hydraulic Control

Hydraulic Filter

(Transmission Lubrication)

6P-4603

Transmission Planetary156-8525

Bypass Switch

9X-7781

Transmission Scavenge Pump

Section 156-8525

Bypass Switch

9X-7781

Pump Drive

2A-6516

Suction Screen

9T-3850

Magnetic Screen

(Transmission)

7T-4554

Air Breather

(Transmission)

6G-0078

Hydraulic Tank

(Torque Converter, Hoist, Brake and Transmission)

161-0536

Air Over Hydraulic Cylinder

(Brake) 8W-3405

Shuttle Valve

8J-6173

Slack Adjuster (Rear)

5T-7670

Service and Parking Brake

(Rear) 5T-4489

Oil Cooler

(Rear Brake Cooling)

141-4108

Check Valve

9T-3752

Accumulator Group

241-3147

Electric Drive Pump:

Parking and Secondary

Brake Release

5T-1060

Electric Drive Pump

Check Valve

9T-3096

Check Valve

138-4733

Screen

6E-5065

Parking and

Secondary

Brake Valve

149-4133

Bypass Switch

9X-7781

Bypass Switch

9X-7781

Bypass Switch

9X-7781

Rear Brake

Cooling Pump

Section 3E-3882

Parking Brake

Release Pump

Selection 6T-6147

Torque Converter, Hoist,

Brake and Transmission

Hydraulic Tank 161-0536

Hoist and Rear Brake

Cooling Gear Pump

139-2454

Torque Converter

Charging Pump

Section 6T-6147

Slack Adjuster

2G-5900

Service and

Parking Brake

(Front) 5T-5070

Service and

Parking Brake

(Front) 5T-5070

Orifice

8W-4042

Hoist Screens

6E-5471

Hoist Screens6E-5471

Counterbalance Valve

(Hoist) 132-7102

Hoist Cylinders

9T-2807

Control Valve

245-1662

Suction Screens9T-3850

Pump Drive

2A-6516

Piston Pump (Steering)6E-5650 - See Steer System

Suction Screen9T-3850

Motor

VENT ORIFICE FORCOUNTERBALANCE VALVE

SIGNAL ORIFICE #2

SIGNAL ORIFICE #1

LOW PRESSURE RELIEF

HIGH PRESSURE RELIEF

DUAL STAGESIGNAL SPOOL

ROD END VENTSLOT ACROSS STEM

MAIN RELIEFDUMP SPOOL

HOLD

RAISE

SNUB

FLOA T

LOWER

BRAKE COOLING RELIEF

LEFT REAR

RIGHT REAR

RIGHT FRONT

LEFT FRONT

TORQUE CONVERTER

LOCK-UP

VALVE

PUMPDRIVEBOX

)(

)()(

)(

Low SteeringPressure Switch

Low Steering PumpPressure Test Port

OIL

SAMPLE

PORT

High SteeringPressure Test Port

P

LSHP HT

T

EF

RL

CRCL

TRANSMISSIONHYD

CONTROLS

PUMPDRIVEBOX

HOIST, BRAKE COOLING, AND TORQUE CONVERTER SYSTEMSTRANSMISSION

STEERING SYSTEM

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

A

B

C

D

E

F

G

H

I

J

17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1

A

B

C

D

E

F

G

H

I

J

K K

THIS SCHEMATIC IS FOR THE 789C OFF HIGHWAY TRUCK

PART #: 158-3405 CHG 01

Components are shown installed on a fully operable machine with the key and engine

off and transmission shifter in neutral.

Steering Tank

155-6660

Steering Tank

Filter 9J-5461

BreakeReleif Valve9T-0818

Transmission Charging Pump Section156-8525

Hydraulic Filter(Transmission Charging)6P-4603

Oil Cooler

(Transmission)

4W-5056

Transmission CoolerInlet Relief Valve2P-2859

Service and Parking

Brake (Rear) 5T-4489

Traction Control

Vlave 9G-9208

Makeup Tank for

Service Brake Oil

6E-1851

Orifice

122-7765

Suction Screen9T-3838

Torque Converter

Scavenge Pump

Section 6T-6147

Torque Converter

Outlet Relief Valve

9W-7403

Hoist, Torque Converter

and Brake Air Breather

8X-4575

P

X

N

Z

B

S

A

S

H

F

E

O

Q

Y

K

L

M

D

C

J

R

G

Auxiliary PowerUnit Port

Right BrakePressureTest Port

Left BrakePressureTest Port