INTERACTIVE SCHEMATIC
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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
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UENR2720
January 2012
Volume 2 of 2: Implement Circuits
Volume 1 of 2: Drive Circuits
938K Wheel Loader
Hydraulic System
SWL1-UP
Printed in U.S.A.© 2012 Caterpillar, All Rights Reserved
COMPONENT AND TAP LOCATIONS (Volume 1)
Description
Part
Number
Machine
Location
Schematic
Location
8,7-
E
17029-063ekarB - pG rotalumuccA
6
-E23596-373egrahC - pG rotalumuccA
4
-C72478-453liO ciluardyH - pG relooC
3
-
D86957-383liO noissimsnarT - pG relooC
3
-
E
517663-943xobraeG - pG retliF
4
-
E
6
14570-863Hydraulic Oil - pG retliF
8
,7-
E7
1
9809-943rotalumuccA ekarB - pG dlofinaM
5
-E815870-743evlaV kcolretnI tatsyH - pG dlofinaM
3
-D
9
13368-653pooL tatsyH - pG dlofinaM
3
-C227703-703)cc511( tatsyH - pG rotoM
1
-
C328467-143)cc071( tatsyH - pG rotoM
8
-C424503-703naF ciluardyH/rotaidaR - pG rotoM
Motor Gp - Radiator/Hydraulic Fan (Reversing) 307-3064 25 C-8
2
-D624162-X9rotcennoC gnihsulF rotoM - pG ecifirO
8
-E
82
7510-243ekarB - pG ladeP
4
-D
929703-703eCharge/ buL - pG pmuP
Pump Gp - Fan/Brake (W/Brake Charging Valve) 307-3058 30 D-7,8
6
-
D
335603-703tatsyH - pG pmuP
8
-D
6
31937-443)egrahC ekarB( erusserP - pG rosneS
6
-
D
,
E
73
8711-943)DWF pooL tatsyH( erusserP - pG rosneS
5
-
C
838711-943)VER pooL tatsyH( erusserP - pG rosneS
7
-E041937-443)ekarB kraP( erusserP - pG rosneS
2
-E342003-853xobraeG - rA noissimsnarT
8
-D54
1523-743rotalumuccA (Fan/Brake Charge) - pG evlaV
6
-C05
8702-843)ssapyB relooC liO dyH( kcehC - pG evlaV
1
-D1
50822-073)gnihsulF tatsyH( kcehC - pG evlaV
Valve Gp - Check (Xmsn Oil Cooler Bypass) 385-9391 58 D-3
7
-
E16
7730-753ekarB kraP - pG evlaV
Component Location Volume 1
Tap
Number
Description
Schematic
Location
4-EerusserP egrahC7P
4-DlliF egrahC8P
3-EegauG SOS xobraeG9P
3-D erusserP evirD drawroF tatsyH01P
2-C erusserP evirD esreveR tatsyH11P
4-BegauG SOS ciluardyH21P
3-EerusserP xobraeG31P
3-EerusserP ebuL 41P
2-EerusserP hctulC51P
8-E erusserP ekarB ecivreS tnorF61P
8-EerusserP ekarB ecivreS raeR71P
8-CerusserP egrahcsiD ekarB/naF91P
8-EerusserP gnigrahC ekarB02P
7-CerusserP esneSdaoL ekarB/naF12P
Tap Location
Pressure and Sampling
Volume 1
5-E350574-321)ylppuS toliP( kcehC - pG evlaV
5
-E565598-663)kcolretnI tatsyH( dioneloS - pG evlaV
COMPONENT AND TAP LOCATIONS (Volume 2)
Description
Part
Number
Machine
Location
Schematic
Location
4-E34107-373toliP - pG rotalumuccA
2
-F40696-373lortnoC ediR - pG rotalumuccA
2
-E52696-373lortnoC ediR - pG rotalumuccA
4
-B69282-852knaT ciluardyH - rehtaerB
6
-D94270-573relpuoC noisuF - pG rednilyC
5
-D015739-353relpuoC ediW - pG rednilyC
3
-F115158-153tliT tfiL hgiH - pG rednilyC
3
-E213583-743tfiL - pG rednilyC
2
-D3125 83-743gnireetS - pG rednilyC
3
-F414583-743tliT - pG rednilyC
7
-D026908-743nruteR emarF raeR - pG dlofinaM
3
-C125905-643gnireetS - pG dlofinaM
2
-E723798-663CP lortnoC ediR - pG ecifirO
2
-C
2-C
13
23
3267-143gnireteM dnaH - pG pmuP
Pump Gp - Hand Metering (W/Dual Mode Steering) 341-7639
7
-B432667-143pmuP tnemelpmI - pG pmuP
Pump Gp - Secondary Steering (W/Integrated Relief) 307-3051 35 C-1
Sensor Gp - Pressure (Implement Pump Discharge) 344-7391 39 E-7
3-C141937-443)gnireetS yramirP( erusserP - pG rosneS
5
,4-A249918-943ciluardyH - pG knaT
3
-D443487-943nruteR emarF tnorF - sA ebuT
6
-E642583-743)tnemelpmI( 2 knaB - pG evlaV
6
-E743583-743)tnemelpmI( 3 knaB - pG evlaV
6
-E844583-743)tnemelpmI( 4 knaB - pG evlaV
4
-F947181-211)rewoL enignE daeD( llaB - pG evlaV
Valve Gp - Check (Implement Backpressure) 352-1045 52 E-7
2-E453101-T9)ylppuS lortnoC ediR( kcehC - pG evlaV
3
-C553101-T9)gnireetS yradnoceS( kcehC - pG evlaV
7
-D654862-291)erusserpkcaB gnireetS( kcehC - pG evlaV
3
-C757440-571)telnI gnireetS( kcehC - pG evlaV
8
-E950686-563kcoL laitnereffiD - pG evlaV
3
-B063054-742edoM lauD - pG evlaV
6
-D268011-253relpuoC kciuQ - pG evlaV
2
-E368799-082lortnoC ediR - pG evlaV
7
-D468327-V6)kcocteP( ffotuhS - pG evlaV
Component Location Volume 2
Tap Location
Pressure and Sampling
Volume 2
Tap
Number
Description
Schematic
Location
P1 Steering Discharge Pressure C-3
P2 Steering Loadsense Pressure C-5
P3 Implement Discharge Pressure E-5
P4 Implement Loadsense Pressure C-6
P5 Implement Pilot Pressure E-5
P6 Quick Coupler Pressure D-5
P18 Differential Lock Pressure E-7
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
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: DRIVE CIRCUITS
SCHEMATIC PART NUMBER: 339-6679, CHANGE: 00, VERSION: -
THIS SCHEMATIC IS FOR THE 938K WHEEL LOADER HYDRAULIC SYSTEM
12345678
A
B
C
D
E
F
12345678
A
B
C
D
E
F
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
PILOT PUMP OUTPUT
LUBE PUMP SUPPLY CIRCUIT
MAIN PUMP OUTPUT
LUBE PUMP CIRCUIT
AUXILIARY 1 CIRCUIT
LOAD SENSE CIRCUIT
STEERING CIRCUIT
FAN/BRAKE CHARGE PUMP
SUPPLY LINE
QUICK COUPLER CIRCUIT
BRAKE CIRCUIT
AUXILIARY 2 CIRCUIT
DRAIN / RETURN LINE
TILT CYLINDER CIRCUIT
LIFT CYLINDER CIRCUIT
HYSTAT CIRCUIT
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
P12
P11
P15
P14
P13
P9
P10
P8
P7
P16
P17
P20
P19
P21
A
T1
U
G
B
T1
T2
F
PU L
T1
E
S
Ms
Mp
M
Secondary
Steer
Steering
Implement
Charge
Pump
Lube
Pump
Hystat
Pump
Sec.
Steering
Rear Drain
Manifold
Front
Manifold
HMU
Pilot Drain
Dual Mode
Steering
To
Imp
Pilot
T2
Hydraulic
Tank
To
Rear
Axle
To
Front
Axle
U
B
M1
G
A
M1
B1 B2
S2
S1
SOS
Y
Z
U
T
E
G
SA
1:1 Drive Ratio
307-3077
(22) MOTOR GP
341-7648
HYSTAT (170cc)
356-8633
(19) MANIFOLD GP
HYSTAT LOOP
356-8633
(19) MANIFOLD GP
HYSTAT LOOP
348-2078
(50) VALVE GP - CHECK
HYD OIL COOLER BYPASS
349-1178
(38) SENSOR GP - PRESSURE
HYSTAT LOOP (REVERSE)
354-8742
(7) COOLER GP
HYDRAULIC OIL
9X-2614
MOTOR FLUSHING
370-2280
(51) VALVE GP-CHECK
HYSTAT FLUSHING
358-3002
(43) TRANSMISSION AR
GEARBOX
307-3079
(29) PUMP GP
CHARGE & LUBE
368-0754
(16) FILTER GP-OIL
HYD OIL
349-3667
(15) FILTER GP-O (BSC)
GEARBOX
366-8955
(65) VALVE GP-SOLENOID
HYSTAT INTERLOCK
123-4750
(53) VALVE-CHECK
PILOT SUPPLY
347-0785
(18) MANIFOLD GP
HYSTAT INTERLOCK
307-3065
(33) PUMP GP
HYSTAT PUMP
349-1178
(37) SENSOR GP-PRESS
HYSTAT LOOP
(FORWARD)
373-6953
(2) ACCUMULATOR GP
CHARGE ACCUMULATOR
HYSTAT (115cc)
(26) ORIFICE GP
(23) MOTOR GP
T
P
G
C
Fan Brake
Valve
M
PSG
A1 A2
LS
F
PG
L1L2 LS
B
X
B
L
R
T
FG
PS1
To Brakes
1.03:1 Drive
Ratio
PS2
360-9207
(1) ACCUMULATOR GP
BRAKE ACCUMULATOR
342-0157
(28) PEDAL GP-BRAKE
349-9089
(17) MANIFOLD GP
BRAKE ACCUMULATOR
344-7391
(40) SENSOR GP-PRESS
PARK BRAKE
357-0377
(61) VALVE GP
PARK BRAKE
344-7391
(36) SENSOR GP
PRESSURE
(BRAKE
CHARGE)
307-3054
(24) MOTOR GP
RADIATOR/HYDRAULIC FAN
307-3064
(25) MOTOR GP
RADIATOR/HYDRAULIC FAN (REVERSING)
307-3058
(30) PUMP GP - FAN/BRAKE
(W/ BRAKE CHARGING VALVE)
347-3251
(45) VALVE GP - ACCUMULATOR
FAN/BRAKE CHARGING
383-7596
(8) COOLER GP
XMSN OIL
385-9391
(58) VALVE GP
CHECK
(COOLER
BYPASS)
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 2 of 2: IMPLEMENT CIRCUITS
SCHEMATIC PART NUMBER: 339-6679, CHANGE: 00, VERSION: -
THIS SCHEMATIC IS FOR THE 938K WHEEL LOADER HYDRAULIC SYSTEM
12345678
A
B
C
D
E
F
12345678
A
B
C
D
E
F
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
PILOT PUMP OUTPUT
LUBE PUMP SUPPLY CIRCUIT
MAIN PUMP OUTPUT
LUBE PUMP CIRCUIT
AUXILIARY 1 CURCUIT
LOAD SENSE CIRCUIT
STEERING CIRCUIT
FAN/BRAKE CHARGE PUMP
SUPPLY LINE
QUICK COUPLER CIRCUIT
BRAKE CIRCUIT
DIFFERENTIAL LOCK CIRCUIT
AUXILIARY 2 CURCUIT
DRAIN / RETURN LINE
TILT CYLINDER CIRCUIT
LIFT CYLINDER CIRCUIT
HYSTAT CIRCUIT
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
M
L1
S1
L4
L3
S2
Lube
Pump
Charge
Pump
P
H
R
T S
Ride Control
Hystat
Pump
M
Tilt Cylinder
Fan Motor
Return
Cooler
Return
Cooler
Bypass
Fan/Brake
Suction
To
Gear
Box
From Gear Box
Park Brake
Valve
TP
LS PP
C1 C2
To
Pp
P
CS
RCS
Lx
Ls
A
A
B
B
B
Tilt Lift
Aux
1
T
C1
C2LS
P
Lift
Cylinders
L2
T
C2C1
P
LP RP
D
SB
B1 B2
B1 B2
S2
T
From
Hystat
Interlock
Valve
To
Charge
Circuit
R
E
A
B
A
Aux
Tg
Steering Pump
Implement Pump
X2
PG
X1
PPG
GP
Fan Motor
Case Drain
Brake Pedal
Valve
1:1 Drive Ratio
2
373-6960
(4) ACCUMULATOR GP
373-6962
(5) ACCUMULATOR GP
RIDE CONTROL
353-9375
(10) CYLINDER GP
WIDE COUPLER
375-0724
(9) CYL GP
FUSION
COUPLER
352-1108
(62) VALVE GP
QUICK
COUPLER
192-2684
(56) VALVE-CHECK
STEERING
BACKPRESSURE
6V-7238
(64) VALVE-SHUTOFF
PETCOCK VALVE
347-8096
(20) MANIFOLD GP
REAR FRAME RETURN
352-1045
(52) VALVE GP - CHECK
IMPLEMENT
BACK PRESSURE
344-7391
(39) SENSOR GP - PRESSURE
IMPLEMENT PUMP
DISCHARGE
365-6860
(59) VALVE GP
DIFFERENTIAL LOCK
347-2352
(46) VALVE GP - BANK 2
IMPLEMENT
347-2353
(47) VALVE GP - BANK 3
IMPLEMENT
347-2354
(48) VALVE GP - BANK 4
IMPLEMENT
341-7662
(34) PUMP GP
IMPLEMENT
349-8199
(42) TANK GP
HYDRAULIC TANK
258-2829
(6) BREATHER
HYDRAULIC TANK
247-4503
(60) VALVE GP
DUAL MODE
STEERING
344-7391
(41) SENSOR GP - PRESS
PRIMARY STEERING
175-0447
(57) VALVE AS - CHECK
STEERING INLET
9T-1013
(55) VALVE GP - CHECK
SECONDARY
STEERING
346-5095
(21) MANIFOLD GP
STEERING
349-7843
(44) TUBE AS
FRONT FRAME
RETURN MANIFOLD
347-3852
(13) CYLINDER GP
STEERING
366-8973
(27) ORIFICE GP
RIDE CONTROL PC
280-9978
(63) VALVE GP
RIDE CONTROL
RIDE CONTROL
9T-1013
(54) VALVE GP - CHECK
RIDE CONTROL SUPPLY
347-3853
(12) CYL GP - LIFT
347-3854
(14) CYL GP - TILT
373-7014
(3) ACCUMULATOR GP
PILOT
112-1817
(49) VALVE GP - BALL
DEAD ENGINE LOWER
351-8515
(11) CYL GP - HIGH LIFT TILT
341-7623
(31) PUMP GP
HAND METERING UNIT
341-7639
(32) PUMP GP
HAND METERING UNIT
(W/DUAL MODE STEERING)
307-3051
(35) PUMP GP
SECONDARY STEERING
(W/ INTEGRATED RELIEF)
P
T
DL
P6
P3
P5
P1
P2
P4
P18
RIGHT SIDE VIEW (Accumulators)
2
1
VIEW ALL CALLOUTS
RIGHT SIDE VIEW
63
5
4
P21
P20
P19
P18
P11
P10
P6
P4
P2
64
62
61
59
56
54
50
49
45
44
42
40
38
37
36
34
33
32
31
30
29
27
26
23
22
20
19
17
13
6
VIEW ALL CALLOUTS
FRONT CYLINDERS VIEW
14
12
11
9
VIEW ALL CALLOUTS
LEFT SIDE VIEW
32
31
P17
P16
P15
P14
P13
P12
P9
P8
P7
P1
65
60
58
57
55
53
51
43 41
35
28
25
24
21
18
16
15
VIEW ALL CALLOUTS
FRONTAL VIEW
49
P5
P3
63
52
48
47
46
39
10
5
4
3
VIEW ALL CALLOUTS
REAR VIEW
8
7
VIEW ALL CALLOUTS
