RENR8709
24 Page, WDB
©
2004 Caterpillar
All Rights Reserved
Printed in U.S.A.
RENR8709
March 2 004
446D
Hydraulic System
446D:
DBL1-UP
Backhoe Loader
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
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 P ILOT
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
MANUAL SHUTOFF
12
15
9
11
3029
67
8
13
14
33 34
5
17
22
4
39
16
19
40
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)
TOP
VIEW
REAR
VIEW
40
40
Pilot Shut Off Valve (40)
Pilot
Shut Off
Solenoid
R912-OR
200-BK
RIDE CONTROL
Accumulator (3) , Pressure Switch (20), Ride Control Valve (38)
Machine Component Locations
Hydraulic Pump Group (19)
Brake Charge Pressure Test Port (AA)
Pump Discharge Pressure Test Port (BB)
Signal Pressure Tap (CC)
Pilot Pressure Test Port (DD)
Valve Group Pilot (35)(36)(37)(38)
Tap Locations
Pressure, Sampling, and Sensor
Tap
Number
Description
Schematic
Location
AA Brake Charge Pressure Test Port A-9
BB Pump Discharge Pressure Test Port B-9
CC Signal Pressure Test Port B-9
DD Pilot Pressure Test Port E-7
Description Media Number
446D Backhoe Loader SEBP3972
Specifications: (Hydraulic & Steering System) RENR8707
Testing and Adjusting: (Hydraulic & Steering System) RENR8708
Specifications: (Axles, Differentials & Brakes) RENR8704
Testing and Adjusting: (Axles, Differentials & Brakes) RENR8705
Schematic: (Electrical System) RENR7781
Related Manuals
Parts Manual:
Machine System:
Electrical System:
10
2
18
21
3
DD
AA
19
BB
CC
3
39
Ride Control
Solenoid
976-OR
200-BK
20
Ride Control
Pressure Switch
F738-WH
200-BK
Description
Part
Number
Machine
Location
Schematic
Location
Accumulator - Brake 9T-6284 1 A-11
Accumulator - Pilot Pressure 149-0686 2 C-5
Accumulator - Ride Ctrl(Attach) 162-3960 3 D-13
Cooler 9Y-1834 4 C-11
Cylinder - Boom 111-8211 5 D-3
Cylinder - Bucket (Standard) 240-6029 6 C-3
Cylinder - Bucket (E-Stick) 240-6030 7 C-3
Cylinder - E-Stick 242-4278 8 B-6
Cylinder - Lift 125-7895 9 E-13, E-14
Cylinder - Stab LH 197-8079 10 C-6
Cylinder - Stab RH 197-8083 11 B-6
Cylinder - Steer 9T-1834 12 D-12
Cylinder - Stick 111-8213 13 B-3
Cylinder - Swing 169-9531 14 D-6
Cylinder - Tilt 100-7844 15 E-12
Filter 6E-5215 16 C-10
Hand Metering Unit(HMU Standard) 240-8206 17 D-11
Hand Metering Unit(HMU Emergency) 241-3757 18 D-11
Pump Gp 240-2612 19 B-10
Switch - Pressure (Ride Control) 131-9203 20 D-14
Switch - Pressure (Brake Fluid) 168-7557 21 B-13
Tank Gp 9R-2294 22 B-11
Valve - Brake 9T-7928 23 B-13
Valve - Charge 9T-3682 24 A-11
Valve - Check 9T-7114 25 E-11
Valve Gp - Cushion Swing 206-3685 26 D-6
Valve Gp - Loader (Lift,Tilt) 240-5977 27 E-11
Valve Gp - Loader (Lift,Tilt,Aux) 240-5978 28 E-11
Valve Gp - Mech (Boom,Stick,Bucket) 240-6800 29 A-3
Valve Gp - Pilot (Boom,Stick,Bucket) 236-1740 30 A-3
Valve Gp - Orifice w/bypass 214-3523 31 E-4
Valve Gp - Pattern Switching 164-2274 32 C-5
Valve Gp - Pilot LH Joystick 185-5916 33 D-5
Valve Gp - Pilot RH Joystick 185-5915 34 B-5
Valve Gp - Pilot (Stab,Swing,Mech:Aux) 239-1437 35 A-7
Valve Gp - Pilot (Stab,Swing,Mech:Aux) 239-1436 36 A-7
Valve Gp - Pilot (Stab,Mech:Swing,Aux) 240-5982 37 A-7
Valve Gp - Pilot (Stab,Mech:Swing,Aux) 240-5984 38 A-7
Valve Gp - Ride Control 190-8315 39 D-13
Valve Gp - Pilot Shut-Off 220-3392 40 C-6
Valve Gp - Stabilizer Pilot 185-5900 41 C-8
Valve Gp - Stabilizer,Pilot Oper Check 246-1604 42 C-6
Component Locations
1
23
24
27
28
20
32
41 42
31
2625
3837
36
35
FRONT VIEW OF CAB
Brake Fluid
Pressure Switch
483-BR
200-BK
RENR8709
24 Page, Color 2, WDB
A
B
C
D
E
F
A
C
D
E
F
B
8
9
10
11
12
13
14
89
10
1112
13
14
1
2
3
4
5
6
7
1
23
4
56
7
HYDRAULIC CIRCUIT COLOR DESCRIPTIONS
Main Pump Output.
Pilot Pump Output.
Load Sense Circuit.
Supply Line.
Drain / Return Line.
Hand Metering Unit Control Circuit.
Lift Cylinder Control Circuit.
Brake Cylinder Control Circuit.
Tilt Cylinder Control Circuit.
Bucket Cylinder Control Circuit.
Boom Cylinder Control Circuit.
Swing Cylinder Circuit.
Auxiliary Cylinder Control Circuit.
Stick Cylinder Control Circuit.
Stabilizer Cylinder Control Circuit.
Stabilizer Cylinder Control Circuit.
E-Stick Cylinder Control Circuit.
THIS SCHEMATIC I S FOR THE 446D BACKHOE LOADER
Part #: 242-2380
Components are shown installed on a fully operable machine with the key and engine
off and transmission shifter in neutral.
LINE PATTERNS
Drain / Return Lines
Component Group
Pilot / Load Sensing Pressure
Pressure Line
Attachment
Air Line
CALLOUTS
Tap s (Pressure, Sampling,Sensor) by letter
Components by number
YY
52
BRAKE CHARGE
PRESSURE
PUMP
PRESSURE
SIGNAL
PRESSURE
PILOT
PRESSURE
XX
XX
XX
PUMP GP
240-2612
VALVE GP
CHARGE
9T-3682
ACCUMULATOR
9T-6284
HMU STD 240-8206
HMU EMERG 240-8206
VALVE GP
RIDE CONTROL
190-8315
CYLINDER GP
STEER
9T-1834
ACCUMULATOR
162-3960
CYLINDER GP
TILT
100-7844
CYLINDER GP
LIFT
125-7895
VALVE GP
CHECK
9T-7114
VALVE GP
LOADER LIFT/TILT
240-5977
VALVE GP
LOADER LIFT/TILT/AUX
240-5978
VALVE GP
BRAKE
9T-7928
TANK GP
HYDRAULIC
9R-2294
COOLER
9Y-1834
FILTER GP
RETURN
6E-5215
VALVE GP-PILOT
239-1437 STAB, SWING, MECH:AUX
239-1436 STAB, SWING, MECH:AUX
240-5982 STAB MECH: SWING, AUX
240-5984 STAB MECH: SWING, AUX
VALVE GP
STABILIZER PILOT VALVE
185-5900
CYLINDER GP
E-STICK
242-4278
CYLINDER GP
STABILIZER RH
197-8083
CYLINDER GP
STABILIZER LH
197-8079
VALVE GP
STABILIZER
246-1604
VALVE GP
LH PILOT
185-5916
VALVE GP
SHUT-OFF
220-3392
ACCUMULATOR
149-0686
CYLIDER GP
SWING
169-9531
VALVE GP
CUSHION SWING
206-3685
VALVE GP
RH PILOT
185-5915
VALVE GP
236-1740 PILOT OPERATED: BOOM, STICK, BUCKET
240-6800 MECHANICAL: BOOM, STICK, BUCKET
CYLINDER GP
STICK
111-8213
CYLINDER GP
BUCKET
240-6029 STANDARD: BORE:95.3 ROD:69.9 STROKE:1011
240-6030 E-STICK: BORE:95.3 ROD:69.9 STROKE:983
CYLINDER GP
BOOM
111-8211
VALVE GP
PATTERN
SWITCHING
164-2274
VALVE GP
214-3523
BRAKE CYLINDER
SWITCH GP
PRESSURE
168-7557
BB
AA
CC
DD
BRAKE CYLINDER
SWITCH GP
PRESSURE
131-9203
