UENR1278-01
May 2012
Volume 1 of 2: Steering and Brake Circuits
994H Wheel Loader
Hydraulic System
DWC1-UP
Printed in U.S.A.© 2012 Caterpillar, All Rights Reserved
UENR1278-01 VOL 1 of 2
36 Page, (Dimensions: 48 inches x 35 inches)
FRONT FRAME AND AXLE - LEFT SIDE VIEW
FRONT FRAME AND AXLE - RIGHT SIDE VIEW REAR FRAME - FRONT
VIEW OF AREA A
VIEW OF AREA B
REAR FRAME - BRAKE COOLING TANK AND BRAKE ACCUMULATORS
VIEW OF AREA A (ACCUMULATORS REMOVED)
VIEW OF AREA B (STEERING PUMP REMOVED)
BRAKE COOLER - REAR FRAME END
REAR AXLE
BRAKE AND STEERING OIL COOLER CIRCUIT
COMPONENT
NOT SHOWN
REAR FRAME - FRONT
VIEW OF AREA A
VIEW OF AREA B
VIEW OF AREA C
COMPONENT
INSIDE VALVE
STEERING AND BRAKE HYDRAULIC TANK AND STEERING PUMPS
COMPONENTS
INSIDE TANK
BEHIND AND BELOW
TANK
53
AA
3322 52 275 23 76
BB
7
48
40
A
B
47
41
38
AA
B
B
45
3
1
16
67
51
50
36
32
8
25
34
78
77
24
56
55
17
49
12
39
59
9
21
63
73
74
54
64
AA
B
B
C
C
10
11
18
70
60
72
71
69
66
65
G1
G2
30
31
68
5
15
44
4
46
37
35
20
19
42
14
43
13
2726
62
61
58
57
6
2829
Description
Part
Number
Machine
Location
Schematic
Location
Accumulator GP - Brake 348-9290 1 E-4
Brake GP - Parking 116-1339 2 J-3
Breather - Hydraulic (Brake Cooling Tank) 9T-1119 3 B-4
Breather - Hydraulic (Steering and Brake Tank) 9T-1119 4 C-7
Connector 143-4218 5 B-13
Connector 8C-0564 6 G-12
Control GP - Foot Brake 305-5531 7 I-6
Cooler - Brake 355-1657 8 C-3
Core GP - Oil Cooler 9Y-8890 9 F-7
C
ylinder GP - Steering (LH) 6E-0529 10 I-14
Cylinder GP - Steering (RH) 9T-9019 11 I-13
Filter GP - Oil 6E-0874 12 F-7
Filter GP - Oil (Hydraulic Case Drain LH) 115-2129 13 B-10
Filter GP - Oil (Hydraulic Case Drain RH) 115-2129 14 B-11
Fitting - Orifice 110-0778 15 B-13
Pump GP - Brake 102-4226 16 C-5
Pump GP - Brake Cooling 116-7341 17 B-3
Pump GP - Secondary Steering 6E-0868 18 G-9
Pump GP - Steering (LH) 263-5065 19 D-10
Pump GP -
Steering (RH) 263-5064 20 C-11
Pump GP - Steering and Brake Oil Cooler 6E-0867 21 D-6
Screen - Front Left 164-3306 22 E-3
Screen - Front Right 164-3306 23 E-2
Screen - Rear Left 164-3306 24 D-3
Screen - Rear Right 164-3306 25 D-2
Screen AS - Return 7J-2656 26 B-7
Screen AS - Return 9T-9227 27 B-8
Screen GP - Steering Pump LH 251-2451 28 F-10
Screen GP - Steering Pump RH 251-2451 29 E-11
Screw - Purge (Steering Cylinder LH) 9F-2167 30 H-13
S
crew - Purge (Steering Cylinder RH) 9F-2167 31 H-13
Sensor GP - Temperature (Brake Cooling Oil) 288-8390 32 B-3
Sensor GP - Temperature (Front Axle Oil) 288-8390 33 J-5
Sensor GP - Temperature (Rear Axle Oil) 288-8390 34 G-5
Sensor GP - Temperature (Steering and Brake Oil) 288-8390 35 B-9
Switch - Oil Level (Brake Cooling) 306-6875 36 B-5
Switch - Oil Level (Steering and Brake) 306-6875 37 B-6
Switch As - Limit (Park Brake)
171-7085 38 I-3
Switch AS - Pressure 255-2282 39 F-6
Switch As - Pressure (Brake) 175-3244 40 H-4
Switch As - Pressure (Park Brake Oil) 327-4608 41 J-2
Switch AS - Pressure (Oil Filter Bypass LH) 339-4361 42 B-10
Switch AS - Pressure (Oil Filter Bypass RH) 339-4361 43 B-11
Switch AS - Pressure (Secondary Steering Pump) 313-5104 44 B-13
Tank GP - Hydraulic (Brake Cooling) 248-2584 45 A-4
Tank GP - Hydraulic (Steering and Bra
ke) 307-4606 46 B-7
Valve GP - Brake Control (Parking) 106-1774 47 I-2
Valve GP - Brake Control (Service) 247-1295 48 I-5
Valve GP - Check 122-3359 49 C-4
Valve GP - Check (Brake Accumlator) 128-6847 50 E-5/D-5
Valve GP - Check (Brake Pump) 9T-6005 51 D-5
Valve GP - Check (Front Left) 9T-3752 52 E-3
Valve GP - Check (Front Right) 9T-3752 53 E-2
Valve GP - Check (Neutralizer, Steering) 149-4617 54 F-13
Valve GP - Check (Rear Left) 9T-
3752 55 C-3
Valve GP - Check (Rear Right) 9T-3752 56 C-2
Valve GP - Check (Steering Pump LH) 6E-1252 57 E-10
Valve GP - Check (Steering Pump RH) 6E-1252 58 D-11
Valve GP - Cooler Bypass 264-6867 59 F-6
Valve GP - Diverter (Secondary Steering) 163-5465 60 G-10
Valve GP - Flow Compensator (Steering Pump LH) 6E-1024 61 E-9
Valve GP - Flow Compensator (Steering Pump RH) 6E-1024 62 D-12
Valve GP - Fluid Sampling 8C-3446 63 E-6
Valve GP
- Pilot (Stic Steering) 249-5615 64 C-13
Valve GP - Pressure Control (Secondary Steering) 1U-2226 65 B-12
Valve GP - Pressure Control (Steering) 1U-2226 66 B-13
Valve GP - Relief (Direct Operated) 367-5058 67 D-5
Valve GP - Relief (Pump Backup) 9J-8225 68 G-12
Valve GP - Relief (Steering Cylinder Crossover) 6E-0859 69 G-14
Valve GP - Relief (Secondary Steering) 9J-0460 70 G-10
Valve GP - Shuttle 4T-1860 71 G-13
Valve GP - Ste
ering 154-5236 72 G-13
Valve GP - Steering Neutralizer (LH) 296-5662 73 E-14
Valve GP - Steering Neutralizer (RH) 296-5662 74 E-13
Wheel GP - Final Drive and Brake (Front Left) 137-3505 75 E-3
Wheel GP - Final Drive and Brake (Front Right) 137-3505 76 E-2
Wheel GP - Final Drive and Brake (Rear Left) 137-3505 77 D-3
Wheel GP - Final Drive and Brake (Rear Right) 137-3505 78 D-2
Component Location
Tap
Number
Description
Schematic
Lo
cation
A Accumulator Pressure H-3
B Service Brake Pressure H-4
C Service Brake Pressure (Front) I-5
D Service Brake Pressure (Rear) G-5
G1 Steering Cylinder Pressure (Left) H-14
G2 Steering Cylinder Pressure (Right) H-13
G3 Left Steering Pump Discharge Pressure E-12
G4 Right Steering Pump Discharge Pressure F-10
G5 Brake Cooling Pump Discharge Pressure B-3
G6 Cooler Pump Discharge Pressure E-6
G7 Front Brake Accumulator Pressure
E-4
G8 Rear Brake Accumulator Pressure D-5
Tap Location
Pressure and Sampling
Check Part Numbers in the Parts Manuals for your Specific Machine.
UENR1278-01 VOL 1 of 2
36 Page, (Dimensions: 48 inches x 35 inches)
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: STEERING AND BRAKE CIRCUITS
SCHEMATIC PART NUMBER: 327-5451, CHANGE: 01, VERSION: - (STEERING)
MEDIA NUMBER: UENR1278-01
THIS SCHEMATIC IS FOR THE 994H WHEEL LOADER HYDRAULIC SYSTEM
248-2712, CHANGE: 03, VERSION: - (BRAKES)
A
B
C
D
E
F
12345678
91011121314
G
H
I
J
12345678
91011121314
A
B
C
D
E
F
G
H
I
J
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
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
BRAKE COOLING CIRCUIT
STEERING PUMP OUTPUT
STEERING AND BRAKE OIL COOLER PUMP OUTPUT
SECONDARY PUMP OUTPUT
STEERING CIRCUIT
SUPPLY LINE
BRAKE CIRCUIT
DRAIN / RETURN LINE
BRAKE PUMP OUTPUT
PARK BRAKE CIRCUIT
ELECTRICAL CIRCUITS
BRAKE RETURN
FRONT BRAKE SUPPLY
REAR BRAKE SUPPLY
PS
HS
PS
HS
(76) WHEEL GP
FINAL DRIVE AND BRAKE (FRONT RIGHT)
137-3505
(1) ACCUMULATOR GP
BRAKE
348-9290
(2) BRAKE GP
PARKING
367-8636
(4) BREATHER
HYDRAULIC
(STEERING AND
BRAKE TANK)
9T-1119
(7) CONTROL GP
FOOT BRAKE
305-5531
(3) BREATHER
HYDRAULIC
(BRAKE
COOLING TANK)
9T-1119
(8) COOLER
BRAKE
355-1657
(9) CORE GP
OIL COOLER
9Y-8890
(12) FILTER GP
OIL
6E-0874
(14) FILTER GP
OIL
(HYDRAULIC CASE DRAIN RH)
115-2129
(74) VALVE GP
STEERING NEUTRALIZER
(RH)
296-5662
(6) CONNECTOR
8C-0564
(15) FITTING
ORIFICE
110-0778
(5) CONNECTOR
143-4218
(29) SCREEN GP
STEERING PUMP RH
251-2451
(28) SCREEN GP
STEERING PUMP LH
251-2451
(22) SCREEN
FRONT LEFT
164-3306
(26) SCREEN AS
RETURN
7J-2656
(27) SCREEN AS
RETURN
9T-9227
(31) SCREW
PURGE
(STEERING CYLINDER RH)
9F-2167
(30) SCREW
PURGE
(STEERING CYLINDER LH)
9F-2167
(11) CYLINDER GP
STEERING (RH)
9T-9019
(10) CYLINDER GP
STEERING (LH)
6E-0529
(35) SENSOR GP
TEMPERATURE
(STEERING AND BRAKE OIL)
288-8390
(34) SENSOR GP
TEMPERATURE
(REAR AXLE OIL)
288-8390
(33) SENSOR GP
TEMPERATURE
(FRONT AXLE OIL)
288-8390
(16) PUMP GP
BRAKE
102-4226
(17) PUMP GP
BRAKE COOLING
116-7341
(21) PUMP GP
STEERING AND BRAKE
OIL COOLER
6E-0867
(18) PUMP GP
SECONDARY STEERING
6E-0868
(19) PUMP GP
STEERING (LH)
263-5065
(20) PUMP GP
STEERING (RH)
263-5064
(46) TANK GP
HYDRAULIC
(STEERING AND BRAKE)
307-4606
(45) TANK GP
HYDRAULIC
(BRAKE COOLING)
248-2584
(44) SWITCH AS
PRESSURE
(SECONDARY
STEERING PUMP)
313-5104
(37) SWITCH
OIL LEVEL
(STEERING AND BRAKE)
306-6875
(36) SWITCH
OIL LEVEL
(BRAKE COOLING)
306-6875
(32) SENSOR GP
TEMPERATURE
(BRAKE COOLING OIL)
288-8390
(39) SWITCH AS
PRESSURE
255-2282
(43) SWITCH AS
PRESSURE
(OIL FILTER BYPASS RH)
339-4361
(38) SWITCH AS
LIMIT
(PARK BRAKE)
171-7085
(40) SWITCH AS
PRESSURE
(BRAKE)
175-3244
(41) SWITCH AS
PRESSURE
(PARK BRAKE OIL)
327-4608
(47) VALVE GP
BRAKE CONTROL
(PARKING)
106-1774
(58) VALVE GP
CHECK
(STEERING PUMP RH)
6E-1252
(54) VALVE GP
CHECK
(NEUTRALIZER, STEERING)
149-4617
(59) VALVE GP
COOLER BYPASS
264-6867
(50) VALVE GP
CHECK
(BRAKE ACCUMULATOR)
128-6847
(49) VALVE GP
CHECK
122-3359
(52) VALVE GP
CHECK (FRONT LEFT)
9T-3752
(51) VALVE GP
CHECK
(BRAKE PUMP)
9T-6005
(62) VALVE GP
FLOW
COMPENSATOR
(STEERING PUMP RH)
6E-1024
(61) VALVE GP
FLOW
COMPENSATOR
(STEERING PUMP LH)
6E-1024
(64) VALVE GP
PILOT
(STIC STEERING)
249-5615
(60) VALVE GP
DIVERTER
(SECONDARY STEERING)
163-5465
(65) VALVE GP
PRESSURE CONTROL
(SECONDARY STEERING)
1U-2226
(66) VALVE GP
PRESSURE
CONTROL
(STEERING)
1U-2226
(70) VALVE GP
RELIEF
(SECONDARY STEERING)
9J-0460
(68) VALVE GP
RELIEF
(PUMP BACKUP)
9J-8225
(67) VALVE GP
RELIEF
(DIRECT OPERATED)
367-5058
(69) VALVE GP
RELIEF
(STEERING CYLINDER
CROSSOVER)
6E-0859
(63) VALVE GP
FLUID SAMPLING
8C-3446
(71) VALVE GP
SHUTTLE
4T-1860
(72) VALVE GP
STEERING
154-5236
(48) VALVE GP
BRAKE CONTROL
(SERVICE)
247-1295
(57) VALVE GP
CHECK
(STEERING PUMP LH)
6E-1252
REAR AXLE
FRONT AXLE
G1
G2
(73) VALVE GP
STEERING NEUTRALIZER
(LH)
296-5662
G3
(13) FILTER
OIL
(HYDRAULIC CASE DRAIN LH)
115-2129
(42) SWITCH AS
PRESSURE
(OIL FILTER BYPASS LH)
339-4361
G4
C
G6
G5
D
B
A
G8
G7
(53) VALVE GP
CHECK (FRONT RIGHT)
9T-3752
(23) SCREEN
FRONT RIGHT
164-3306
(75) WHEEL GP
FINAL DRIVE AND BRAKE (FRONT LEFT)
137-3505
(78) WHEEL GP
FINAL DRIVE AND BRAKE (REAR RIGHT)
137-3505
(77) WHEEL GP
FINAL DRIVE AND BRAKE (REAR LEFT)
137-3505
(24) SCREEN
REAR LEFT
164-3306
(25) SCREEN
REAR RIGHT
164-3306
(55) VALVE GP
CHECK (REAR LEFT)
9T-3752
(56) VALVE GP
CHECK (REAR RIGHT)
9T-3752
VIEW OF AREA A
TAPS
D
AA
G8
G6
G5
C
G7
G4
G3
UENR1278-01
May 2012
Volume 2 of 2: Implement System
994H Wheel Loader
Hydraulic System
DWC1-UP
Printed in U.S.A.© 2012 Caterpillar, All Rights Reserved
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)
PUMP
(2 - SECTION)
SPRING
(ADJUSTABLE)
VARIABILITY LINE RESTRICTION
(VARIABLE)
PRESSURE
COMPENSATION
PUMP
(VARIABLE & PRESSURE
COMPENSATED)
MEASUREMENT
PRESSURE TEMPERATURE FLOW
ROTATING SHAFTS
UNIDIRECTIONAL BIDIRECTIONAL
PUSH - PULL LEVER PEDALGENERAL MANUAL PUSH BUTTON SPRING
FIXED
DISPLACEMENT
VARIABLE DISPLACEMENT
NON-COMPENSATED
UNIDIRECTIONAL
BIDIRECTIONAL
VALVE ENVELOPES VALVE PORTS
FLUID CONDITIONERPUMP OR MOTOR
FLUID POWER SYMBOLS
UNIDIRECTIONAL
BIDIRECTIONAL
RELEASED PRESSURE
EXTERNAL RETURN INTERNAL RETURN
REMOTE SUPPLY PRESSURE
SIMPLIFIED
HYDRAULIC PUMPS
ACCUMULATORS
SPRING LOADED GAS CHARGED
SOLENOID
OR MANUAL
SOLENOID
& PILOT
SOLENOID &
PILOT OR MANUAL
SOLENOID SERVO THERMAL DETENT
HYDRAULIC & PNEUMATIC CYLINDERS
DOUBLE ACTINGSINGLE ACTING
BASIC
SYMBOL
SPRING
LOADED
CHECK VALVES
2 POSITION
INFINITE
POSITIONING
FLOW IN ONE
DIRECTION
FLOW IN
EITHER
DIRECTION
3 POSITION
CROSS
FLOW
PARALLEL
FLOW
INTERNAL PASSAGEWAYS
NORMAL POSITION
AB
PT
AB
PT
SHIFTED POSITION INFINITE POSITION
CONTROL VALVES
ATTACHMENT
MANUAL SHUTOFF
SHUTTLE PILOT
CONTROLLED
MAIN AUX
LINE RESTRICTION
(VARIABLE & PRESSURE
COMPENSATED)
MANUAL CONTROL SYMBOLS
HYDRAULIC MOTORS
FLUID STORAGE RESERVOIRS
CROSSING & JOINING LINES
VALVES
PILOT CONTROL SYMBOLS
COMBINATION CONTROLS
BASIC COMPONENT SYMBOLS
ENERGY TRIANGLES
HYDRAULIC PNEUMATIC
INTERNAL
SUPPLY PRESSURE
COMPLETE
FIXED
DISPLACEMENT
VARIABLE DISPLACEMENT
NON-COMPENSATED
HYDRAULIC SYMBOLS (ELECTRICAL)
ELECTRICAL SYMBOLS TABLE
325-AG135 PK-14
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
WIRE
WIRE
(EXAMPLE VALVE)
CURRENT STANDARD
TRANSDUCER
(FLUID)
M
ELECTRIC MOTORTRANSDUCER
(GAS / AIR)
G
GENERATOR
PRESSURE SWITCH ELECTRICAL WIREPRESSURE SWITCH
(ADJUSTABLE)
TEMPERATURE
SWITCH
PRESSURE
SWITCH
TEMPERATURE
SWITCH
LEVEL
SWITCH
FLOW
SWITCH
ELECTRICAL SYMBOLS (ELECTRICAL)
A
CIRCUIT NUMBER
IDENTIFICATION
WIRE
COLOR
WIRE GAUGE
T
UENR1278-01 VOL 2 of 2
36 Page, (Dimensions: 48 inches x 35 inches)
FRONT FRAME - REAR RIGHT VIEW
FRONT FRAME - REAR LEFT VIEW
HYDRAULIC TANK LIFT AND TILT CYLINDERS
HYDRAULIC OIL COOLER COMPONENTS
AND LOAD SENSING VALVES
TAP LOCATIONS
OIL COOLING
114
144
120
115
146
112
118
85
140
81
138
162
139
155
83
175
133
134
87
167
143
185
119
177
186
173
92
117
190
161
170
126
93
80
150
160
88
181
86
182
82
171
141
168
124
174
84
180
154
184
165
179
131
132
153
164
130
183
178
129
95969798
99
90
91
100 101 102
107 108 109 110
103 104 105 106
156
163
151
157
166
149
159
148
135
125
128
158
116
137
89
142
122127123
94
147
111
169
121
136
113
172
145
187
G5
G6
G4
G3
G2
G1
G9
G8
G7
AA
C
C
VIEW OF AREA A
VIEW OF AREA C
VIEW OF AREA B
B
B
176
188
189
Tap
Number
Description
Schematic
Location
G1 Right Implement Pump Discharge Pressure E-9
G2 Center Implement Pump Discharge Pressure E-8
G3 Left Rear Implement Pump Discharge Pressure D-6
G4 Left Front Implement Pump Discharge Pressure D-6
G5 Implement Pilot Pressure E-12
G6 Lift Rod End Cylinder Pressure I-10
G7 Lift Head End Cylinder Pressure I-10
G8 Tilt Rod End Cylinder Pressure J-9
G9 Tilt Head End Cylinder Pressure J-
10
Tap Location
Pressure and Sampling
Valve GP - Breaker Relief (RH) 220-0812 160 A-8
Valve GP - Check 239-1132 161 G-11
Valve GP - Check 4T-5896 162 I-11
Valve GP - Check and Relief (Operator Center) 275-4098 163 D-7
Valve GP - Check and Relief (Operator Left) 1 275-4098 164 D-5
Valve GP - Check and Relief (Operator Left) 2 275-4098 165 C-5
Valve GP - Check and Relief (Operator Right) 275-4098 166 D-9
Valve GP - Control (Opera
tor Left Valve) 326-7714 167 I-11
Valve GP - Control (Operator Right Valve) 326-7715 168 I-5
Valve GP - Cooler Bypass (Hydraulic Oil) 264-6867 169 C-12
Valve GP - Fluid Sampling 8C-3446 170 D-12
Valve GP - Makeup (Right Lift Cylinder Rod End) 160-7439 171 I-5
Valve GP - Manual Lower 112-1817 172 H-11
Valve GP - Pressure Reducing 370-0438 173 I-11
Valve GP - Relief (Hydraulic Oil Cooler Bypass) 245-4891 174 C-11
Valve GP - Relief
(Left Lift Cylinder Head End) 352-2906 175 I-10
Valve GP - Relief (Left Tilt Cylinder Head End) 129-8293 176 I-9
Valve GP - Relief (Left Tilt Cylinder Rod End) 352-2907 177 I-9
Valve GP - Relief (Operator Left) 1 143-8912 178 D-6
Valve GP - Relief (Operator Left) 2 143-8912 179 C-6
Valve GP - Relief (Right Lift Cylinder Head End) 352-2906 180 I-5
Valve GP - Relief (Right Tilt Cylinder Head End) 129-8293 181 I-6
Valve GP - R
elief (Right Tilt Cylinder Rod End) 352-2907 182 I-6
Valve GP - Relief (Operator Center) 143-8912 183 D-8
Valve GP - Relief (Operator Right) 143-8912 184 D-9
Valve GP - Sequence 336-4809 185 E-12
Valve GP - Shuttle 4T-1860 186 I-10
Valve GP - Solenoid 151-7455 187 G-11
Valve GP - Solenoid (Load Sensing Operator Left Valve) 173-7455 188 F-10
Valve GP - Solenoid (Load Sensing Operator Right Valve) 173-7455 189 G-6
Description
Part
N
umber
Machine
Location
Schematic
Location
Accumulator GP - Pilot 245-2975 80 F-12
Actuator GP - Pilot Control (Dump, Operator Left Valve, Left Tilt Cylinder) 217-6720 81 G-9
Actuator GP - Pilot Control (Dump, Operator Right Valve, Right Tilt Cylinder) 217-6720 82 H-6
Actuator GP - Pilot Control (Lower, Operator Left Valve, Left Lift Cylinder) 217-6720 83 G-10
Actuator GP - Pilot Control (Lower, Operator Right Valve, R
ight Lift Cylinder) 217-6720 84 H-5
Actuator GP - Pilot Control (Rack, Operator Left Valve, Left Tilt Cylinder) 217-6720 85 H-9
Actuator GP - Pilot Control (Rack, Operator Right Valve, Right Tilt Cylinder) 217-6720 86 I-6
Actuator GP - Pilot Control (Raise, Operator Left Valve, Left Lift Cylinder) 217-6720 87 H-10
Actuator GP - Pilot Control (Raise, Operator Right Valve, Right Lift Cylinder) 217-6720 88 H-5
Connector
AS 222-6869 89 E-12
Connector AS - Left Lift Cylinder Head End 8I-6347 90 J-10
Connector AS - Left Lift Cylinder Rod End 8I-6347 91 J-10
Connector AS - Operator Left Valve 8I-6347 92 H-9
Connector AS - Operator Right Valve 8I-6347 93 H-7
Cooler GP - Brake 179-3642 94 C-12
Cylinder GP - Lift Left (Extended High Lift) 322-1579 95 J-10
Cylinder GP - Lift Left (High Lift) 288-4468 96 J-10
Cylinder GP - Lift Left (Standard Lift) 193-4076 97 J-10
Cylinder GP - Lift L
eft (Super High Lift) 247-4565 98 J-10
Cylinder GP - Lift Right (Extended High Lift) 322-1579 99 J-5
Cylinder GP - Lift Right (High Lift) 288-4468 100 J-5
Cylinder GP - Lift Right (Standard Lift) 193-4076 101 J-5
Cylinder GP - Lift Right (Super High Lift) 247-4565 102 J-5
Cylinder GP - Tilt Left (Extended High Lift) 322-3142 103 J-9
Cylinder GP - Tilt Left (High Lift) 341-6034 104 J-9
Cylinder GP - Tilt Left (Standard Lift)
353-3913 105 J-9
Cylinder GP - Tilt Left (Super High Lift) 353-4654 106 J-9
Cylinder GP - Tilt Right (Extended High Lift) 322-3141 107 J-6
Cylinder GP - Tilt Right (High Lift) 341-6033 108 J-6
Cylinder GP - Tilt Right (Standard Lift) 353-3912 109 J-6
Cylinder GP - Tilt Right (Super High Lift) 353-4653 110 J-6
Filter GP - Cooler 6E-0874 111 C-12
Filter GP - Hydraulic Case Drain 1 115-2129 112 C-9
Filter GP - Hydraulic Case Drain
2 115-2129 113 C-8
Filter GP - Oil 1 341-1861 114 B-9
Filter GP - Oil 2 341-1861 115 B-7
Filter GP - Transmission Oil 353-0454 116 E-12
Fitting - Quick Disconnect (Operator Center) 6V-3965 117 C-9
Fitting - Quick Disconnect (Operator Left) 1 6V-3965 118 C-6
Fitting - Quick Disconnect (Operator Right) 6V-3965 119 C-10
Gauge - Sight (Oil) 147-9560 120 A-9
Pump GP - Implement (Operator Center) 315-3144 121 E-8
Pump GP - Implement (Opera
tor Right) 325-9799 122 E-7
Pump GP - Implement (Operator Right) 330-9389 123 E-10
Pump GP - Pilot System Hydraulic Oil Cooler 245-0963 124 D-12
Screen AS 9T-9227 125 A-10
Screen AS - Operator Center 6E-5065 126 C-8
Screen AS - Operator Right 6E-5065 127 C-10
Screen GP 7J-2656 128 A-11
Screen GP - Implement (Operator Center) 251-2451 129 E-8
Screen GP - Implement (Operator Left) 1 251-2451 130 D-6
Screen GP - Implement (Operator Lef
t) 2 251-2451 131 C-6
Screen GP - Implement (Operator Right) 251-2451 132 E-10
Screw - Purge (Left Tilt Cylinder Head End) 9F-2167 133 I-9
Screw - Purge (Left Tilt Cylinder Rod End) 9F-2167 134 J-9
Sensor - Oil Level 306-6875 135 A-9
Sensor AS - Temperature (Hydraulic Oil) 256-6453 136 A-12
Sensor GP - Pressure (Implement Pilot) 349-1178 137 E-12
Sensor GP - Pressure (Left Lift Cylinder Head End) 349-1178 138 J-10
Sensor GP - Pr
essure (Left Lift Cylinder Rod End) 349-1178 139 J-10
Sensor GP - Pressure (Operator Left Valve) 344-7391 140 H-9
Sensor GP - Pressure (Operator Right Valve) 344-7391 141 H-7
Switch AS - Pressure (Filter Bypass) 349-6097 142 E-12
Switch AS - Pressure (Oil Filter Bypass) 1 339-4361 143 C-9
Switch AS - Pressure (Oil Filter Bypass) 2 339-4361 144 B-9
Switch AS - Pressure (Oil Filter Bypass) 3 339-4361 145 C-8
Switch AS - Pressu
re (Oil Filter Bypass) 4 339-4361 146 B-7
Switch GP - Pressure (Cooler Filter Bypass) 255-2282 147 C-12
Tank - Expansion (LH) 321-7838 148 A-8
Tank - Expansion (RH) 321-7838 149 A-9
Tank GP - Hydraulic 336-6665 150 A-11
Tube AS 322-1673 151 G-5
Valve - Operator Left Valve 6E-1291 152 G-10
Valve - Operator Left Valve 1 102-4156 153 H-9
Valve - Operator Left Valve 2 102-4156 154 I-10
Valve - Operator Right Valve 6E-1291 155 G-6
Valve - Op
erator Right Valve 1 102-4156 156 H-6
Valve - Operator Right Valve 2 102-4156 157 H-6
Valve GP - Breaker Relief 133-1963 158 A-6
Valve GP - Breaker Relief (LH) 220-0812 159 A-7
Component Location
Fitting - Quick Disconnect (Operator Left) 2 6V-3965 190 C-6
Check Part Numbers in the Parts Manuals for your Specific Machine.
UENR1278-01 VOL 2 of 2
36 Page, (Dimensions: 48 inches x 35 inches)
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 SYSTEM
SCHEMATIC PART NUMBER: 327-5422, CHANGE: 02, VERSION: -
MEDIA NUMBER: UENR1278-01
THIS SCHEMATIC IS FOR THE 994H WHEEL LOADER HYDRAULIC SYSTEM
A
B
C
D
E
F
12345678
91011121314
G
H
I
J
12345678
91011121314
A
B
C
D
E
F
G
H
I
J
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
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
PILOT PUMP OUTPUT
BRAKE COOLING
OPERATOR LEFT PUMP OUTPUT
CENTER PUMP OUTPUT
SUPPLY LINE
LIFT CYLINDER CIRCUIT
DRAIN / RETURN LINE
OPERATOR RIGHT PUMP OUTPUT
TILT CYLINDER CIRCUIT
RACK
DUMP
RAISE
LOWER
RACK
DUMP
RAISE
LOWER
HYDRAC
ON/OFF
B
G2
R
T2
T1
M1
S
Q MIN
A
G1
R
T2
T1
M1
Q
M
A
X
Q MIN
L1L2
CW
Mb
Ma
Q MAX
Q MIN
CW
S1
D1
SA2
SA1
24 VDC
EHV
M2g
M1g
P1
ACTR
Q MAX
Q MIN
CCW
S1
D1
SA2
SA1
24 VDC
EHV
M2g
M1g
P1
ACTR
(80) ACCUMULATOR GP
PILOT
245-2975
(88) ACTUATOR GP
PILOT CONTROL
(RAISE,
OPERATOR RIGHT VALVE,
RIGHT LIFT CYLINDER)
217-6720
(94) COOLER GP
BRAKE
186-0058
CYLINDER GP - LIFT (RIGHT)
(101) 193-4076 (STANDARD LIFT)
(100) 288-4468 (HIGH LIFT)
(102) 247-4565 (SUPER HIGH LIFT)
(99) 322-1579 (EXTENDED HIGH LIFT)
CYLINDER GP - LIFT (LEFT)
(97) 193-4076 (STANDARD LIFT)
(96) 288-4468 (HIGH LIFT)
(98) 247-4565 (SUPER HIGH LIFT)
(95) 322-1579 (EXTENDED HIGH LIFT)
CYLINDER GP - TILT (LEFT)
(105) 353-3913 (STANDARD LIFT)
(104) 341-6034 (HIGH LIFT)
(106) 353-4654 (SUPER HIGH LIFT)
(103) 322-3142 (EXTENDED HIGH LIFT)
CYLINDER GP - TILT (RIGHT)
(109) 353-3912 (STANDARD LIFT)
(108) 341-6033 (HIGH LIFT)
(110) 353-4653 (SUPER HIGH LIFT)
(107) 322-3141 (EXTENDED HIGH LIFT)
(113) FILTER GP
HYDRAULIC
CASE DRAIN 2
115-2129
(115) FILTER GP
OIL 2
341-1861
(111) FILTER GP
COOLER
6E-0874
(116) FILTER GP
TRANSMISSION OIL
353-0454
(120) GAUGE
SIGHT
(OIL)
147-9560
(89) CONNECTOR AS
8I-6347
(151) TUBE AS
322-1673
(123) PUMP GP
IMPLEMENT
(OPERATOR LEFT)
325-9799
(122) PUMP GP
IMPLEMENT
(OPERATOR RIGHT)
330-9389
(121) PUMP GP
IMPLEMENT
(OPERATOR CENTER)
315-3144
(124) PUMP GP
PILOT SYSTEM
HYDRAULIC OIL
COOLER
245-0963
(125) SCREEN AS
9T-9227
(128) SCREEN GP
7J-2656
(127) SCREEN AS
OPERATOR RIGHT
6E-5065
(126) SCREEN AS
OPERATOR CENTER
6E-5065
(134) SCREW
PURGE
(LEFT TILT CYLINDER ROD END)
9F-2167
(135) SENSOR
OIL LEVEL
306-6875
(136) SENSOR AS
TEMPERATURE
(HYDRAULIC OIL)
256-6453
(139) SENSOR GP
PRESSURE
(LEFT LIFT CYLINDER ROD END)
349-1178
(141) SENSOR GP
PRESSURE
(OPERATOR RIGHT VALVE)
344-7391
(93) CONNECTOR AS
OPERATOR RIGHT VALVE
8I-6347
(90) CONNECTOR AS
LEFT LIFT CYLINDER HEAD END
8I-6347
(137) SENSOR GP
PRESSURE
(IMPLEMENT PILOT)
349-1178
(146) SWITCH AS
PRESSURE
(OIL FILTER
BYPASS) 4
339-4361
(147) SWITCH GP
PRESSURE
(COOLER FILTER BYPASS)
255-2282
(142) SWITCH AS
PRESSURE
(FILTER BYPASS)
349-6097
(148) TANK GP
EXPANSION
(LH)
321-7838
(150) TANK GP
HYDRAULIC
336-6665
(119) FITTING
QUICK DISCONNECT
(OPERATOR RIGHT)
6V-3965
(117) FITTING
QUICK DISCONNECT
(OPERATOR CENTER)
6V-3965
(155) VALVE
OPERATOR RIGHT VALVE
6E-1291
(157) VALVE
OPERATOR RIGHT VALVE 2
102-4156
(161) VALVE GP
CHECK
239-1132
(162) VALVE GP
CHECK
4T-5896
(169) VALVE GP
COOLER BYPASS
(HYDRAULIC OIL)
264-6867
(167) VALVE GP
CONTROL
(OPERATOR LEFT VALVE)
326-7714
(168) VALVE GP
CONTROL
(OPERATOR RIGHT VALVE)
326-7715
(171) VALVE GP
MAKEUP
(RIGHT LIFT CYLINDER ROD END)
160-7439
(172) VALVE GP
MANUAL LOWER
112-1817
(173) VALVE GP
PRESSURE REDUCING
370-0438
(158) VALVE GP
BREAKER RELIEF
133-1963
(160) VALVE GP
BREAKER RELIEF
(RH)
220-0812
(174) VALVE GP
RELIEF
(HYDRAULIC OIL
COOLER BYPASS)
245-4891
(184) VALVE GP
RELIEF
(OPERATOR RIGHT)
143-8912
(183) VALVE GP
RELIEF
(OPERATOR CENTER)
143-8912
(180) VALVE GP
RELIEF
(RIGHT LIFT CYLINDER HEAD END)
352-2906
(181) VALVE GP
RELIEF
(RIGHT TILT CYLINDER HEAD END)
129-8293
(182) VALVE GP
RELIEF
(RIGHT TILT CYLINDER ROD END)
352-2907
(132) SCREEN GP
IMPLEMENT
(OPERATOR RIGHT)
251-2451
(129) SCREEN GP
IMPLEMENT
(OPERATOR CENTER)
251-2451
(185) VALVE GP
SEQUENCE
336-4809
(170) VALVE
FLUID SAMPLING
8C-3446
(186) VALVE GP
SHUTTLE
4T-1860
(189) VALVE GP
SOLENOID
(LOAD SENSING
OPERATOR RIGHT VALVE)
173-7455
(188) VALVE GP
SOLENOID
(LOAD SENSING
OPERATOR LEFT VALVE)
173-7455
(187) VALVE GP
SOLENOID
151-7455
(166) VALVE GP
CHECK AND
RELIEF
(OPERATOR RIGHT)
275-4098
(163) VALVE GP
CHECK AND
RELIEF
(OPERATOR CENTER)
275-4098
(149) TANK GP
EXPANSION
(RH)
321-7838
(159) VALVE GP
BREAKER RELIEF
(LH)
220-0812
(145) SWITCH AS
PRESSURE
(OIL FILTER
BYPASS) 3
339-4361
(114) FILTER GP
OIL 1
341-1861
(143) SWITCH AS
PRESSURE
(OIL FILTER
BYPASS) 1
339-4361
(144) SWITCH AS
PRESSURE
(OIL FILTER
BYPASS) 2
339-4361
(112) FILTER GP
HYDRAULIC
CASE DRAIN 1
115-2129
(118) FITTING
QUICK DISCONNECT
(OPERATOR LEFT) 1
6V-3965
(164) VALVE GP
CHECK AND RELIEF
(OPERATOR LEFT) 1
275-4098
(165) VALVE GP
CHECK AND RELIEF
(OPERATOR LEFT) 2
275-4098
(178) VALVE GP
RELIEF
(OPERATOR LEFT) 1
143-8912
(179) VALVE GP
RELIEF
(OPERATOR LEFT) 2
143-8912
(131) SCREEN GP
IMPLEMENT
(OPERATOR LEFT) 2
251-2451
(130) SCREEN GP
IMPLEMENT
(OPERATOR LEFT) 1
251-2451
(84) ACTUATOR GP
PILOT CONTROL
(LOWER,
OPERATOR RIGHT VALVE,
RIGHT LIFT CYLINDER)
217-6720
(86) ACTUATOR GP
PILOT CONTROL
(RACK,
OPERATOR RIGHT VALVE,
RIGHT TILT CYLINDER)
217-6720
(82) ACTUATOR GP
PILOT CONTROL
(DUMP,
OPERATOR RIGHT VALVE,
RIGHT TILT CYLINDER)
217-6720
(156) VALVE
OPERATOR RIGHT VALVE 1
102-4156
(140) SENSOR GP
PRESSURE
(OPERATOR LEFT VALVE)
344-7391
(92) CONNECTOR AS
OPERATOR LEFT VALVE
8I-6347
(154) VALVE
OPERATOR LEFT VALVE 2
102-4156
(177) VALVE GP
RELIEF
(LEFT TILT CYLINDER ROD END)
352-2907
(85) ACTUATOR GP
PILOT CONTROL
(RACK,
OPERATOR LEFT VALVE,
LEFT TILT CYLINDER)
217-6720
(81) ACTUATOR GP
PILOT CONTROL
(DUMP,
OPERATOR LEFT VALVE,
LEFT TILT CYLINDER)
217-6720
(153) VALVE
OPERATOR LEFT VALVE 1
102-4156
(152) VALVE
OPERATOR LEFT VALVE
6E-1291
(176) VALVE GP
RELIEF
(LEFT TILT CYLINDER HEAD END)
129-8293
(175) VALVE GP
RELIEF
(LEFT LIFT CYLINDER HEAD END)
352-2906
(133) SCREW
PURGE
(LEFT TILT CYLINDER HEAD END)
9F-2167
(138) SENSOR GP
PRESSURE
(LEFT LIFT CYLINDER HEAD END)
349-1178
(91) CONNECTOR AS
LEFT LIFT CYLINDER ROD END
8I-6347
(87) ACTUATOR GP
PILOT CONTROL
(RAISE, OPERATOR LEFT VALVE, LEFT LIFT CYLINDER)
217-6720
(83) ACTUATOR GP
PILOT CONTROL
(LOWER,
OPERATOR LEFT VALVE,
LEFT LIFT CYLINDER)
217-6720
G5
G6
G7
G9
G8
G2
Q
M
A
X
G3
G4
AIR
BLEED
AIR
BLEED
AIR
BLEED
AIR
BLEED
AIR
BLEED
AIR
BLEED
AIR
BLEED
AIR
BLEED
G1
P1
P
D

Leave a Reply

Your email address will not be published. Required fields are marked *