RENR7784-00
20Page,B/W,DGM
©
2004 Caterpillar
All Rights Reserved
Printed in U.S.A.
RENR7784
January 2004
428D Backhoe Loader
Hydraulic System
DSX1-UP
BXC1-UP
MBM1-UP
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
FLUID POWER SYMBOLS
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
AB
PT
AB
PT
SHIFTED POSITION
INFINITE POSITION
CONTROL VALVES
ATTACHMENT
Hydraulic Symbols (Electrical)
Electrical Symbols Table
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
T
Pressure
Symbol
Temperature
Symbol
Level
Symbol
Flow
Symbol
Electrical Symbols (Electrical)
SINGLE TILT LOADER WITH SIDE SHIFT BACKHOE
428D PARALLEL LIFT LOADER OR
26
28
29
68910
5
17
3422 23 24
27 30
7
13
14 15 16 18 19 20 21
1
25
50
5756555452
6261605958
6766656463
53
51
11 12
4948
46434140
34 35
44 45
33 36
37 38
31
42
2
47
Item No Description Part No.
1 Rear Steering Cylinder (If Equipped) ------
2 All Wheel Steer Valve (If Equipped) 121-4449
3 Steering Cylinder All Wheel Drive (If Equipped) ------
4 Steering Cylinder 167-4235
5 Multipurpose Bucket Cylinder (If Equipped) 185-1839
6 Broom Motor (If Equipped) ------
7 Auxiliary Control Valve 191-4035
8 Coupler Cylinder 178-3713
9 Coupler Valve 138-1979
10 Diverter Valve 201-0947
11 Tilt Cylinder for Parallel Lift 192-3884
12 Tilt Cylinder for Single Tilt 206-3555
Line Relief Valve for Head End of Single Tilt Cylinder
Line Relief Valve for Rod End of Parallel Lift Cylinder
14 Auxiliary Relief Valve 9T-0704
Line Relief Valve for Head End of Parallel Lift Cylind
e
Line Relief Valve for Rod End of Single Tilt Cylinder
16 Loader Tilt Control Valve 191-4032
17 Lift Cylinder Loader 192-3791
18 Loader Lift Control Valve 130-6520
19 Steering Priority Valve 188-7471
20 Two Bank Valve for Loader 185-5913
21 Three Bank Valve for Loader 185-5914
22 Pressure Switch 131-9203
23 Ride Control Solenoid Valve 190-8315
24 Ride Control Accumulator 162-3960
25 All Wheel Steer Pressure Switch 128-5091
26 Steering Metering Pump 238-8550
27 Piston Pump 185-5918
28 Hydraulic Tank 240-9716
29 Hydraulic Oil Cooler ------
30 Hydraulic Oil Filter 143-0421
Back Pressure Check Valve (Return Oil) 178-7480
Back Pressure Check Valve (Hammer Option) 178-7481
33 Stabilizer Contol Valve 222-0364
34 Stabilizer Cylinder 173-4565
35 Stabilizer Cylinder 173-4565
36 Stabilizer Control Valve 222-0364
37 Stabilizer Contol Valve (Two Bank) 185-5898
38 Pressure Reducing Valve 239-2226
40 Solenoid Valve (TUV) 179-5593
41 Inlet Cover 202-2236
42 Boom Cylinder 206-3630
43 Line Relief Valve for the Rod End of Boom Cylinder 6E-6285
44 Swing Cylinder 191-8161
45 Swing Cylinder 191-7735
46 Line Relief Valve for the Rod End of Swing Cylinder 137-9466
48 Backhoe Bucket Cylinder 206-0514
49 Backhoe Bucket Cylinder Extendable Stick 206-0518
50 Line Relief for Head End of Bucket Cylinder 187-0524
51 Stick Cylinder 206-0509
52 Line Relief for Head End of Stick Cylinder 187-0528
53 Extendable Stick Cylinder (If Equipped) 191-7725
54 Extendable Stick Control Valve 190-3450
55 End Cover 193-9189
56 Side Shift Lock Valve 3E-8622
57 Stick Control Valve 204-0533
58 Line Relif for the Rod End of Stick Cylinder 187-0529
59 Backhoe Bucket Control Valve 193-3124
60 Line Relief for the Rod End of Bucket Cylinder 187-0527
61 Backhoe Control Valve (Four Bank Valve)
203-5486
62 Backhoe Control Valve (Five Bank Valve)
203-5488
63 Backhoe Control Valve (Six Bank Valve)
203-5487
64 Swing Control Valve
166-7950
65 Boom Control Valve
204-0532
66 Line Relief for the Head End of the Boom Cylinder
187-0523
67 Extendable Stick Control Valve (If Equipped) 190-3450
68 Filter with Indicator
224-6812
69 Temperature Switch
7N-0758
70 Tilt Valve
191-4032
71 Backhoe Control Valve (Four Bank Valve)
185-5908
72 Backhoe Control Valve (Five Bank Valve)
185-5909
73 Backhoe Control Valve (Six Bank Valve)
185-5910
74 Valve Group (Cushion Relief)
206-3685
75 End Cover - Inlet (BH Valves without TUV)
116-1317
31
COMPONENT LIST
13
15
187-0532
197-3124
TAP LOCATIONS
Pressure, Sampling, and Sensor
Tap
Number
Description
Schematic
Location
FF PUMP SIGNAL PRESSURE TEST PORT C-9
GG PUMP PRESSURE TEST PORT B-9
Description Media Number
428D Backhoe Loader (DSX & BXC) SEBP3969
428D Backhoe Loader (MBM) SEBP3970
Specifications: (Hydraulic & Steering System) RENR7778
Testing and Adjusting: (Hydraulic & Steering System) RENR7779
Specifications: (Axles, Differentials & Brakes) RENR7776
Testing and Adjusting: (Axles, Differentials & Brakes) RENR7777
Schematic: (Electrical system) RENR7781
Related Manuals
Parts Manual:
Machine System:
Electrical System:
RENR7784-00
20 Page, B/W, DGM
A
C
D
E
F
B
8
9
10
11
89
10
11
1
2
3
4
5
6
7
1
23
4
56
7
A
B
C
D
E
F
THIS SCHEMATIC IS FOR THE 428D, Backhoe Loader
Part #: 201-6838 CHG02
Components are shown installed on a fully operable machine with the key and engine
off and transmission shifter in neutral.
P
T
49
42
44
48
51
53
54
52
50
46
43
59
58
57
60
6465
66
67
62
63
61
AUX BOOM
SWING
BUCKET
STICK
E-STICK
55
56
73
72
71
40
41
45
75
S3
S1
74
T
NOT USED
WITH AWS
USED WITH
AWS
SIGNAL
PRESSURE
T1
(Y)
(C)
ACC
H
R
PS
(B)
T
PUMP
PRESSURE
HMU
AWS VALVE
PUMP
LIFT
TILT
AUX
1
2
30
29
28
27
5
3B
19
18
16
17
13
15
14
5
4
7
11
31
3
S1
S2
S3
T3
23
22
24
70
10
9
8
6
F1
F2
R1
R2
LS
RS
LS
RS
FRONT AXLE
(CYLINDER IS IN
FRONT OF AXLE)
FRONT OF MACHINE
68
69
REPLACES STANDARD FILTER
ON CAB DELUXE MODELS
REAR AXLE
(CYLINDER IS IN
FRONT OF AXLE)
T1
PILOT
PRESSURE
T3
USED WITH
AWS
USED WITH
NON-AWS
38
STABILIZER
STABILIZER
36
34
35
S2
37
33
12
FF
GG
20
21
