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X
EC-C3
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E-C60
EC-C1
E-C61
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©
2010 Caterpillar, All Rights Reserved
Printed in U.S.A.
SENR6654-01
March 2010
990 And 990 Series II Wheel Loader
Hydraulic System
7HK1-UP
4FR1-UP
Page 1 of 2
COMPONENT LOCATION
Description
Part
Number
Machine
Location
Schematic
Location
Accumulator (Brake Supply)
100-6909 27
C-8
Accumulator (Ride Control, Optional)
6E4185 23
D-5
Accumulator Gp
9D2632 14
C-8
Cooler
148-8977 24
B-7
Cyl Gp - Lift
9T9569 20
E-6
Cyl Gp - Tilt
9T9570 19
E-6
Filter
4T3134 26
B-7
Pump Gp - Brake/Pilot
6E4657 9
B-8
Pump Gp - Tandem Piston
6E3321 2
B-6
Tank Gp - Filter
9T9554 1
B-7
Valve Gp - Breather
6E3528 25
B-6
Valve Gp - Check 1
9T3096 18
E-6
Valve Gp - Cmb
9T9551 10
C-8
Valve Gp - Control
6E5834 5
D-7
Valve Gp - Pilot
6E3796 15
E-8
Valve Gp - Pressure Cont (Dead Engine Lower)
6E3078 17
E-6
Valve Gp - Relief 1
133-1665 3
B-6
Valve Gp - Relief 2
133-1666 4
B-6
Valve Gp - Relief 3
142-4281 6
C-6
Valve Gp - Relief 4
9T9196 7
D-6
Valve Gp - Relief 5
6E3185 8
C-6
Valve Gp - Relief 6
6E6293 13
C-8
Valve Gp - Relief 7
116-6399 28
B-8
Valve Gp - Shuttle
6R0442 12
C-8
Valve Gp - Shuttle (Dead Engine Lower)
4T1860 16
E-6
Valve Gp - Solenoid (Ride Control, Optional)
152-8340 22
C-5
Valve Gp - Unloading
117-7761 11
C-8
Valve Gp (Ride Control, Optional)
9T9552 21
C-5
Implement And Brake Supply
Page 2 of 2
COMPONENT LOCATION
Description
Part
Number
Machine
Location
Schematic
Location
Cooler
148-8978 44
C-2
Cylinder Gp - Left
6E1244 43
E-4
Cylinder Gp - Right
9T9568 42
E-3
Filter
4T3134 46
C-2
Motor Gp - Fan
159-7166 51
D-1
109-4197
6E4469
Pump Gp - Steer
6E1542 30
C-2
Pump Gp - Supplemental
101-4007 38
D-2
Tank Gp - Steer
6E4683 29
C-2
Valve - Diverter
2U7345 37
E-2
Valve Gp - Breaker - Relief
6E3528 47
C-2
Valve Gp - Check 2
111-7775 41
D-4
Valve Gp - Check 3
104-7108 55
C-3
Valve Gp - Cooler Bypass
6E1454 45
C-2
Valve Gp - Fan Control
6E4679 52
C-1
Valve Gp - Makeup
101-9012 49
D-1
Valve Gp - Neutralizer
9T7426 40
C-4
Valve Gp - Pilot
143-2855 39
C-4
Valve Gp - Press Reducing
6E4286 35
D-3
Valve Gp - Press Reducing
6E4680 53
C-1
Valve Gp - Relief 8
100-4335 32
D-3
Valve Gp - Relief 9
6E3985 33
D-4
Valve Gp - Relief 10
6E3986 36
D-2
Valve Gp - Sel And Press Control
6E5566 48
C-3
Valve Gp - Shuttle
4T1860 34
D-3
Valve Gp - Solenoid
3E8574 54
C-1
6E2925
6E2923
Valve Gp - Steer
31 D-2
Steering And Fan Drive
Pump Gp - Fan
50 C-1
TAP LOCATION
Tap
Number
Description
Schematic
Location
J Steer Pilot Supply Pressure Tap C-3
K Steer Pump Cutoff D-3
L Fan Pump Cutoff C-1
A Implement Relief - Front Pump Pressure Tap C-5
B Implement Relief - Relief Rear Pressure Tap B-5
C Brake Accumulator C-8
D Implement Pilot Supply C-8
E Tilt Cylinder - Head End E-6
F Tilt Cylinder - Rod End D-6
G Lift Cylinder - Head End E-6
H Lift Cylinder - Rod End E-6
I Ride Control Signal C-5
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 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 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 ACTINGSINGLE 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
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
12345678
A
B
C
D
E
F
12345678
A
B
C
D
E
F
LINE PATTERNS
Drain / Return Lines
Component Group
Pilot / Load Sensing Pressure
Pressure Line
Attachment
Air Line
CALLOUTS
Taps (Pressure, Sampling,Sensor) by letter
YY
DRAIN / RETURN LINE
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
LIFT PUMP OUTPUT
TILT PUMP OUTPUT
STEERING CIRCUIT
BRAKE/PILOT PUMP OUTPUT
PRIMARY STEERING PUMP CIRCUIT
SCAVENGE PUMP
FAN PUMP OUTPUT
SUPPLY LINE
TILT CYLINDER CIRCUIT
SECONDARY STEERING CIRCUIT
LOAD SENSING CIRCUIT
LIFT CYLINDER CIRCUIT
STEERING / FAN DRIVE
IMPLEMENT / BRAKE SUPPLY
B
A
E
F
D
C
J
L
K
LEFT
NEUTRALIZER
WARNING
SWITCH
HS
PS
RIGHT
NEUTRALIZER
RIGHT
TURN
STEERING
CYLINDERS
FLUID SAMPLING VALVE
STEER
17
17
1
1
FLUID SAMPLING PORT
BRAKE RETURN LINE
LIFT
BRAKE SUPPLY
PRESSURE PORTS
TILT
PRESSURE SWITCH PORT
LEVER LOCKS
PS
HS
RACK BACK
RAISE
DUMP
LOWER
G
I
H
(15) VALVE GP
PILOT
6E-3796
(17) VALVE GP
PRESSURE CONT
(DEAD ENGINE LOWER)
6E-3078
(5) VALVE GP
CONTROL
6E-5834
(28) VALVE GP
RELIEF 7
116-6399
(12) VALVE GP
SHUTTLE
6R-0442
(11) VALVE GP
UNLOADING
117-7761
(9) PUMP GP
BRAKE/PILOT
6E-4657
(8) VALVE GP
RELIEF 5
6E-3185
(7) VALVE GP
RELIEF 4
9T-9196
(23) ACCUMULATOR GP
RIDE CONTROL
6E-4185
(27) ACCUMULATOR GP
BRAKE SUPPLY
100-6909
(14) ACCUMULATOR GP
9D-2632
(10) VALVE GP
CMB
9T-9551
(13) VALVE GP
RELIEF 6
6E-6293
(6) VALVE GP
RELIEF 3
142-4281
(18) VALVE GP
CHECK 1
9T-3096
(16) VALVE GP
SHUTTLE
(DEAD ENGINE LOWER)
4T-1860
(37) VALVE GP
DIVERTER
2U-7345
(31) VALVE GP
STEER
6E-2925
6E-2923
(36) VALVE GP
RELIEF 10
6E-3986
(33) VALVE GP
RELIEF 9
6E-3985
(34) VALVE GP
SHUTTLE
4T-1860
(32) VALVE GP
RELIEF 8
100-4335
(35) VALVE GP
PRESS REDUCING
6E-4286
(41) VALVE GP
CHECK 2
111-7775
(40) VALVE GP
NEUTRALIZER
9T-7426
(39) VALVE GP
PILOT
143-2855
(48) VALVE GP
SEL AND
PRESS
CONTROL
6E-5566
(49) VALVE GP
MAKEUP
101-9012
(52) VALVE GP
FAN CONTROL
6E-4679
(53) VALVE GP
PRESS REDUCING
6E-4680
(47) VALVE GP
BREAKER RELIEF
6E-3528
(50) PUMP GP
FAN
109-4197
6E-4469
(46) FILTER GP
4T-3134
(29) TANK GP
STEER
6E-4683
(45) VALVE GP
COOLER
BYPASS
6E-1454
(44) COOLER GP
148-8978
(30) PUMP GP
STEER
6E-1542
(55) VALVE GP
CHECK 3
104-7108
(38) PUMP GP
SUPPLEMENTAL
101-4007
(54) VALVE GP
SOLENOID
3E-8574
(51) MOTOR GP
FAN
159-7166
(43) CYLINDER GP
LEFT
6E-1244
(42) CYLINDER GP
RIGHT
9T-9568
(21) VALVE GP
RIDE CONTROL
9T-9552
(22) VALVE GP
SOL (RIDE
CONTROL)
152-8340
(2) PUMP GP
TANDEM PISTON
6E-3321
(25) VALVE GP
BREATHER
6E-3528
(24) COOLER GP
148-8977
(26) FILTER GP
4T-3134
(1) TANK GP
FILTER
9T-9554
(3) VALVE GP
RELIEF 1
133-1665
(4) VALVE GP
RELIEF 2
133-1666
(19) CYLINDER GP
TILT
9T-9570
(20) CYLINDER GP
LIFT
9T-9569
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.
SCHEMATIC PART NUMBER: 133-6593, CHANGE: 04, VERSION: -
MEDIA NUMBER: SENR6654-01
THIS SCHEMATIC IS FOR THE 990 AND 990 SERIES II WHEEL LOADER HYDRAULIC SYSTEM
990
IMPLEMENT AND BRAKE SUPPLY
28
27
26
25
24
23
22
21
20
19
1817
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
H
I
CD
A
B
F
G
E
VIEW ALL CALLOUTS
STEERING AND FAN DRIVE
990
55
54
53
52
51
50
49
48
47
46
45
44
43
42
41
40 39
38
37
36
35
34
33
32
31
30
29
K
L
J
VIEW ALL CALLOUTS
