diagrama hidraulico

1. INTERACTIVE SCHEMATIC
The Bookmarks panel will allow you to
quickly navigate to points of interest.
Click on any text that is BLUE and underlined.
These are hyperlinks that can be used to navi-
gate the schematic and machine views.
When only one callout is showing on a machine view this
button will make all of the callouts visible. This button is
located in the top right corner of every machine view page.
VIEW ALL CALLOUTS
Cover Page
Information
Schematic
Machine Views
Component Table
Tap Table
Fluid Power Symbols
Electrical Symbols
Front Frame
Rear Frame
Tap Views
Features
Options
Bookmarks X
EC-C3
EC-C2 E-C60
EC-C1
E-C61
To set your screen resolution do the following:
RIGHT CLICK on the DESKTOP.
Select PROPERTIES.
CLICK the SETTINGS TAB.
MOVE THE SLIDER under SCREEN RESOLUTION
until it shows 1024 X 768.
CLICK OK to apply the resolution.
This document is best viewed at a
screen resolution of 1024 X 768.
FUNCTION
Zoom In
HOTKEYS (Keyboard Shortcuts)
Zoom Out
Fit to Page
Hand Tool
“CTRL” / “+”
KEYS
“CTRL” / “-”
“CTRL” / “0” (zero)
“SPACEBAR” (hold down)
Find “CTRL” / “F”

2. Hydraulic System
© 2002 Caterpillar, All Rights Reserved Printed in U.S.A.
Volume 2 of 2: Steering and Brake
Volume 1 of 2: Implement and Axle Oil Cooler System
RENR2172-02
May 2002
988G Wheel Loader
BNH1-Up
2TW1-Up

3. Volume 1 of 2 - IMPLEMENT AND AXLE OIL
COOLER SYSTEM
COMPONENT LOCATION
Description
Part
Number
Machine
Location
Schematic
Location
Lift Cylinder 1
173-8613 49 E-6
Tilt Cylinder 1
152-1644 50
Lift Cylinder 1
173-8612 51
Front Axle NA 52 E-1
Main Control Valve 2
212-8712 53
Pressure Reducing Valve 6E-4286 54
Shuttle Valve 4T-1860 55
Brake Oil Cooler 173-6753 56 E-2
Check Valve 130-9704 57 E-2
Brake Oil Cooler Fan Motor 178-1602 58 D-2
Brake Oil Filter 183-6194 59 D-2
Line Relief Valve (Lift Cylinder Head End) 125-9349 60 D-6
Line Relief Valve (Tilt Cylinder Rod End) 117-0161 61
Line Relief Valve (Tilt Cylinder Head End) 117-0160 62
Line Relief Valve (Auxiliary) 172-5481 63
Line Relief Valve (Auxiliary) 172-5481 64
Check Valve 9T-5134 65
Solenoid Valve 149-2610 66
Brake Oil Cooler Pump 187-3707 67 D-1
Line Relief Valve (Lift Cylinder Rod End) 117-0161 68 D-6
Actuator (Lift, Tilt, Auxiliary) 217-6720 69 D-5,D-6
Rear Axle NA 70 C-1
Check Valve 9T-3096 71
Float Valve 100-6731 72
Float Check Valve 6E-1291 73 C-7
Actuator (Lift, Tilt, Auxiliary) 217-6719 74 C-6,C-5
Main Relief Valve 117-0159 75
Ride Control Valve 3
199-3131 76
Ride Control Solenoid Valve 3
152-8340 77 C-3
Ride Control Accumulator 3
219-7983 78 C-3
Check Valve 104-7108 79
Solenoid Valve 149-2610 80
Pilot On/Off Solenoid Valve 151-7455 81
Ball Valve (Manual Lower) 112-1817 82
Implement Pump 219-7225 83
Implement Pump Shuttle Valve 175-2791 84
Implement Pump Flow Control Valve 205-3998 86 B-5
Implement Pump Solenoid Valve 195-3739 85 B-5
C-7
C-6
C-4
C-3
B-7
B-6
A-6
B-5
E-5
D-7
D-6
D-6
D-5
D-2
Implement Pump Case Drain Filter 166-4647 87 A-4
Logger machines use 168-6942 and 168-6943 lift cylinders
and 191-3846 tilt cylinder.
For attachments use 212-8721 and 212-8746 main control valves.
Ride Control is an optional attachment.
E-4
1
2
3

4. Volume 2 of 2 - STEERING AND BRAKE
Page 1 of 2
COMPONENT LOCATION
Description
Part
Number
Machine
Location
Schematic
Location
Left Cylinder Group 133-8173
Right Cylinder Group 135-3288
Rear Axle NA 2 E-4
Front Axle NA 3 E-3
Parking Brake 4E-8525 4 E-2
5 E-4
6 E-3
Foot Brake Control 169-8258 7 E-3
Parking Brake Valve 106-1774 8 D-2
Relief Valve 9T-7419 9 D-7
Shuttle Valve 4T-1860 10 D-6
Steering Valve 133-8608
Steering Valve with Secondary Steering 1
133-8609
Tanden Brake Valve 200-0866 12 D-3
Pressure Switch Parking Brake 3E-6452 13 E-2
Secondary Steering Diverter Valve 1
2U-7345 14 D-5
Relief Valve 6E-6188 15 D-6
Secondary Steering Relief Valve 6E-3986 16 D-5
Pressure Reducing Valve 6E-4286 17 D-6
Secondary Steering Pump 1
150-7585 18 C-5
Pilot Relief Valve 186-6218 19 C-4
Brake Accumulator 220-1432 20 D-3
Pressure Switch 3E-7693 21 C-2
Steering Neutralizer Check Valve 149-4617 22 C-7
9T-3096
104-7108
Secondary Steering Selector Valve 1
6E-5566 24 C-6
Secondary Steering is an optional attachment.
Hi ambient package is an optional attachment.
EU attachment.
1
11
23
E-7
D-5
C-6
131-0427
Temperature Sensor
Check Valve
1
2
3

5. Volume 2 of 2 - STEERING AND BRAKE
Page 2 of 2
COMPONENT LOCATION
Description
Part
Number
Machine
Location
Schematic
Location
Cooler 164-0058 25 C-4
Gear Motor 139-6825
C-4
Piston Motor 2
213-5268
Brake Accumulator Charging Valve 133-7102 27 C-3
Right Steering Neutralizer Valve 146-7571 28 C-7
Left Steering Neutralizer Valve 146-7571 29 C-7
176-7521
176-7520
Oil Filter 115-2129 31 C-4
Cooler Bypass Valve 6E-1454 32 C-4
196-1172
9T-3752
Steering Pilot Valve 143-2855 34 B-7
Steering Pump 153-9624 35 B-5
Air Purge Tap Steering Pump NA 36 B-5
Hydraulic Oil Sampling Valve 8C-3446 37 B-3
Oil Filter 166-4647 38 B-5
Oil Filter 166-4647 39 B-4
Check Valve 3G-8607 40 B-2
Breaker Relief Valve 9T-0818
Breaker Relief Valve 3
220-0812
Expansion Tank 3
220-2948 42 B-4
Pressure and Flow Compensator Valve 191-2929 43 B-3
Hydraulic Tank Manifold 152-3870 44 A-5
Hydraulic Tank 153-3602 45 A-5
Fan Drive Pump 152-7767
Fan Drive Pump 2
215-5721
Thermostatic Valve 152-7202 47 B-3
BrakePilot Pump 177-8924 48 A-2
46
C-5
B-4
Pressure and Flow Compensator Valve
Check Valve
26
30
C-3
41
A-3
33
Secondary Steering is an optional attachment.
Hi ambient package is an optional attachment.
EU attachment.
1
2
3

6. Volume 1 of 2 - IMPLEMENT AND AXLE OIL
COOLER SYSTEM
TAP LOCATION
Tap
Number
Description
Schematic
Location
II Lift Rod End
JJ Lift Head End
KK Auxiliary Line Relief
LL Auxiliary Line Relief
MM Implement Relief B-6
E-6
D-5

7. Volume 2 of 2 - STEERING AND BRAKE
TAP LOCATION
Tap
Number
Description
Schematic
Location
AA Rear Brake Pressure
BB Front Service Brake Pressure
CC Front Brake Pressure
DD Rear Brake Pressure
EE Steering Pilot Supply C-4
FF Steering Pump Discharge C-6
GG Brake Pump Discharge C-3
HH Fan Drive Pump Discharge B-3
D-4
C-3

8. FLUID POWER SYMBOLS
ONE POSITION TWO POSITION THREE POSITION
VENTED PRESSURIZED RETURN ABOVE FLUID LEVEL RETURN BELOW FLUID LEVEL
LINES CROSSING LINES JOINING
TWO-WAY THREE-WAY FOUR-WAY
SPRING CONTROL VALVES RESTRICTION LINE RESTRICTION
(FIXED)
2-SECTION PUMP
MAIN AUX.
SPRING
(ADJUSTABLE)
VARIABILITY LINE RESTRICTION
(VARIABLE)
LINE RESTRICTION
VARIABLE 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 PEDAL
GENERAL 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 CONDITIONER
PUMP or MOTOR
FIXED
DISPLACEMENT
VARIABLE DISPLACEMENT
NON-COMPENSATED
UNIDIRECTIONAL
BIDIRECTIONAL
VALVES
PILOT CONTROL SYMBOLS
RELEASED PRESSURE
EXTERNAL RETURN INTERNAL RETURN
REMOTE SUPPLY PRESSURE
SIMPLIFIED COMPLETE INTERNAL
SUPPLY PRESSURE
ACCUMULATORS
SPRING LOADED GAS CHARGED
SOLENOID
or MANUAL
SOLENOID
and PILOT
SOLENOID and
PILOT or MANUAL
COMBINATION CONTROLS
SOLENOID SERVO THERMAL DETENT
HYDRAULIC AND PNEUMATIC CYLINDERS
DOUBLE ACTING
SINGLE ACTING
BASIC
SYMBOL
SPRING
LOADED
CHECK VALVES
TWO
POSITION
INFINITE
POSITIONING
FLOW IN ONE
DIRECTION
FLOW ALLOWED IN
EITHER DIRECTION
THREE
POSITION
CROSS
FLOW
PARALLEL
FLOW
INTERNAL PASSAGEWAYS
NORMAL POSITION
A B
P T
A B
P T
SHIFTED POSITION INFINITE POSITION
CONTROL VALVES
ATTACHMENT
MANUAL SHUTOFF
SHUTTLE PILOT
CONTROLLED

9. ELECTRICAL SYMBOLS
Hydraulic Symbols (Electrical)
325-AG135 PK-14
Circuit Identification
Number
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 Color
Circuit Number
Identification
B A
Wire
Wire
(EXAMPLE VALVE)
Current Standard
Transducer
(Fluid)
Transducer
(Gas / Air)
G
Generator
Electrical Wire
Pressure Switch
M
Electric Motor
Pressure Switch
(Adjustable)
Temperature Switch
Pressure
Symbol
Temperature
Symbol
Level
Symbol
Flow
Symbol
Electrical Symbols (Electrical)
T

10. Components are shown installed on a fully operable machine with the key and engine off, transmission shifter
in neutral and with parking brake set.
Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.
VOLUME 1 of 2: IMPLEMENT AND AXLE OIL COOLER SYSTEM
SCHEMATIC PART NUMBER: 114-5109 (IMPLEMENT SYSTEM), CHANGE: 05, VERSION: -
SCHEMATIC PART NUMBER: 184-1638 (AXLE OIL COOLER SYSTEM ), CHANGE: 02, VERSION: -
MEDIA NUMBER: RENR2172-02
THIS SCHEMATIC IS FOR THE 988G WHEEL LOADER HYDRAULIC SYSTEM
A
B
C
D
E
1
2
3
4
5
6
7
A
B
C
D
E
1
2
3
4
5
6
7
LINE PATTERNS
Drain / Return Lines
Component Group
Pilot / Load Sensing Pressure
Pressure Line
CALLOUTS
Taps (Pressure, Sampling, Sensor - by letter)
YY
(52) VALVE GP - CONTROL
138-1234
Callout Number
(Machine Location from
Component LocationsTable)
Component
Name
Part Number
PUMP CASE
AIR PURGE
PUMP CASE
FILL PORT
RIDE
CONTROL
RACK
LOWER
DUMP
RAISE
X1
X2
X3
X4
X5
H717-BR
H716-WH
H714-OR
H716-WH
E920-BR
H716-WH
H716-WH
H713-PK
E919-YL
H716-WH
H716-WH
H707-YL
975-WH
976-OR
F05567
(52) FRONT AXLE
(67) PUMP GP
GEAR
187-3707
(70) REAR AXLE
(56) CORE AS
173-6753
(58) MOTOT GP
GEAR (FAN)
178-1602
(57) VALVE GP
CHECK
130-9704
(59) FILTER GP
OIL
183-6194
(66) VALVE GP
SOLENOID
149-2610
(65) VALVE GP
CHECK
9T-5134
AXLE OIL COOLER SYSTEM
IMPLEMENT SYSTEM
(79) VALVE GP
CHECK
104-7108
(80) VALVE GP
SOLENOID
149-2610 (81) VALVE GP
SOLENOID
151-7455
(82) VALVE GP
MANUAL
112-1817
(83) PUMP GP
219-7225
(84) VALVE GP
SHUTTLE
175-2791
(85) VALVE GP
SOLENOID
195-3739
(86) FLOW CONTROL
205-3998
(87) FILTER GP
166-4647
(73) VALVE GP
CHECK
6E-1291
(74) ACTUATOR GP
PILOT CONTROL
217-6719
(74) ACTUATOR GP
PILOT CONTROL
217-6719
(74) ACTUATOR GP
PILOT CONTROL
217-6719
(75) VALVE GP
RELIEF (MAIN)
117-0159
(76) VALVE GP
RIDE CONTROL
199-3131
(77) VALVE GP
SOLENOID
(RIDE CONTROL)
152-8340
(78) ACCUMULATOR GP
(RIDE CONTROL)
219-7983
(71) VALVE GP
CHECK
9T-3096
(72) VALVE GP
FLOAT
100-6731
(69) ACTUATOR GP
PILOT CONTROL
217-6720
(69) ACTUATOR GP
PILOT CONTROL
217-6720
(69) ACTUATOR GP
PILOT CONTROL
217-6720
(68) VALVE GP
RELIEF (LIFT)
117-0161
(60) VALVE GP
RELIEF (LIFT)
125-9349
(62) VALVE GP
RELIEF (TILT)
117-0160
(63) VALVE GP
RELIEF (AUXILIARY)
172-5481
(64) VALVE GP
RELIEF (AUXILIARY)
172-5481
(51) CYLINDER GP
(LIFT)
(50) CYLINDER GP
(TILT)
(49) CYLINDER GP
(LIFT)
(53) VALVE GP
MAIN CONTROL
212-8712
(54) VALVE GP
PRESSURE REDUCING
6E-4286
(55) VALVE GP
SHUTTLE
4T-1860
(61) VALVE GP
RELIEF (TILT)
117-0161
MM
II JJ
KK LL
CONNECTED TO VOLUME 2 (GRID LOCATION A-7)
CONNECTED TO VOLUME 2 (GRID LOCATION A-7)
CONNECTED TO VOLUME 2 (GRID LOCATION A-7)
CONNECTED TO VOLUME 2 (GRID LOCATION A-7)
CONNECTED TO VOLUME 2 (GRID LOCATION A-7)

11. Components are shown installed on a fully operable machine with the key and engine off, transmission shifter
in neutral and with parking brake set.
Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.
VOLUME 1 of 2: IMPLEMENT AND AXLE OIL COOLER SYSTEM
SCHEMATIC PART NUMBER: 114-5109 (STEERING), CHANGE: 05, VERSION: -
SCHEMATIC PART NUMBER: 156-9680 (BRAKE), CHANGE: 03, VERSION: -
MEDIA NUMBER: RENR2172-02
THIS SCHEMATIC IS FOR THE 988G WHEEL LOADER HYDRAULIC SYSTEM
A
B
C
D
E
1
2
3
4
5
6
7
A
B
C
D
E
1
2
3
4
5
6
7
LINE PATTERNS
Drain / Return Lines
Component Group
Pilot / Load Sensing Pressure
Pressure Line
CALLOUTS
Taps (Pressure, Sampling, Sensor - by letter)
YY
(52) VALVE GP - CONTROL
138-1234
Callout Number
(Machine Location from
Component LocationsTable)
Component
Name
Part Number
(45) TANK GP
HYDRAULIC
153-3602
BRAKE SCHEMATIC
PUMP
CASE
FILL
PORT
X
LEFT
NEUTRALIZER
RIGHT
NEUTRALIZER
SWITCH
STEERING SCHEMATIC
X1
X2
X3
X4
X5
K983-BU
201-BK
446-PU
K983-BU
201-BK
429-YL
F722-OR
F721-GY
998-BR
102-RD
604-OR
164-WH
202-BK
H722-GN
201-BK
432-PK
C491-PU
G756-YL
202-BK
Position Sensor
Left Brake
Stop Lamp
Switch
Right Brake
Switch
STOP STOP
WARNING
F05566
(44) TANK AS
152-3870 (46) PUMP GP
PISTON
(HYDRAULIC FAN)
152-7767
(48) PUMP GP
GEAR
(PILOT,BRAKE)
177-8924
(47) VALVE
THERMOSTAT
(HYDRAULIC FAN)
152-7202
(40) VALVE GP
CHECK
3G-8607
(43) VALVE GP
PRESSURE AND FLOW
COMPENSATOR
191-2929
(42) TANK GP
EXPANSION
220-2948
(41) VALVE GP
RELIEF BREAKER
9T-0818
(EU ATTACH) 220-0812
(34) VALVE GP
STEERING PILOT
143-2855
(28) VALVE GP
STEERING
NEUTRALIZER
146-7571
(29) VALVE GP
STEERING
NEUTRALIZER
146-7571
(22) VALVE GP
CHECK (STEERING
NEUTRALIZER)
149-4617
(9) VALVE GP
RELIEF
9T-7419
(1) CYLINDER GP (1) CYLINDER GP
(10) VALVE GP
SHUTTLE
4T-1860
(15) VALVE GP
RELIEF
6E-6188
(17) VALVE GP
PRESSURE REDUCING
6E-4286
(11) VALVE GP
STEERING
133-8608
(14) VALVE GP
SECONDARY STEERING
DIVERTER
2U-7345
(16) VALVE GP
SECONDARY STEERING
RELIEF
6E-3986
(18) PUMP GP
SECONDARY
STEERING
150-7585
(23) VALVE GP
CHECK
9T-3096
(24) VALVE GP
SEC STEERING
SELECTOR
6E-5566
(35) PUMP GP
STEERING
153-9624
(30) VALVE GP
PUMP CONTROL
(PRESSURE
COMPENSATOR)
176-7521
(36) AIR PURGE
TAP
(38) FILTER GP
OIL
166-4647
(39) FILTER GP
OIL
166-4647
(31) FILTER GP
OIL
115-2129
(19) VALVE GP
PILOT RELIEF
186-6218
(20) ACCUMULATOR GP
220-1432
(20) ACCUMULATOR GP
220-1432
(21) SWITCH AS
PRESSURE
3E-7693
(27) VALVE GP
ACCUMULATOR
133-7102
(25) COOLER GP
HYDRAULIC OIL
164-0058
(26) MOTOR GP
GEAR
139-6825
(33) VALVE GP
CHECK
196-1172
(37) VALVE GP
FLUID SAMPLING
8C-3446
(32) VALVE GP
COOLER BYPASS
6E-1454
(2) REAR AXLE
(5) SENSOR GP
TEMPERATURE
131-0427
(7) CONTROL GP
FOOT BRAKE
169-8258
(3) FRONT AXLE
(8) VALVE GP
BRAKE CONTROL
106-1774
(13) SWITCH AS
PRESSURE
(PARKING BRAKE OIL)
3E-6452
(4) BRAKE GP
PARKING
4E-8525
(12) VALVE GP
BRAKE CONTROL
(SERVICE)
200-0866
(6) SENSOR GP
TEMPERATURE
131-0427
HH
GG
CC DD
EE
AA
BB
FF

12. MACHINE COMPONENT LOCATIONS - IMPLEMENT AND AXLE OIL
COOLER SYSTEM
MM
MM
LL
LL
KK
KK
JJ
JJ
II
II
87
87
86
86
85
85
84
84
83
83
82
82
81
81
80
80
79
79
78
78
77
77
76
76
75
75
74
74
73
73
72
72
71
71
70
70
70
70
69
69
68
68
67
67
66
66
65
65
64
64
63
63
62
62
61
61
60
60
59
59
58
57
56
56 55
55
54
54
53
53
52
52
51
51
50
50
49
49
VIEW ALL CALLOUTS

13. MACHINE COMPONENT LOCATIONS - STEERING AND BRAKE
HH
HH
GG
GG
FF
FF
EE
EE DD
DD
DD
CC
CC
CC
BB
BB
BB
AA
AA
AA
48
48
47
47
46
46
45
45
44
44
43
43
42
42
41
41
40
40
39
39
38
38
37
37
36
36
35
35
34
34
33
33
32
32
31
31
30
30
29
29
28
28
27
27
26
26
25
25
24
24
23
23
22
22
21
21
20
20
19
19
18
18
17
17
16
16
15
15
14
14
13
13
12
12
11
11
10
10
9
9
8
8
7
7
6
6
5
5
4
4
3
3
2
2
1
1
VIEW ALL CALLOUTS