KENR7658-01October 2008

Printed in U.S.A.

420E and 430E Backhoe LoaderHydraulic System

© 2008 Caterpillar, All Rights Reserved

420E:PRA1-UPPHC1-UP

430E:SCD1-UPRLN1-UP

Component Tables

ITEM NAME PART NUMBER SCHEMATIC LOCATION1 PUMP GP. 267-27552 HYDRAULIC TANK 297-12333 TANK GROUP 297-12324 HYDRAULIC COOLER 304-78475 FILTER 226-97476 HMU 210-6240

7 FRONT 214-5097

8A ST 228-35098B PL/IT 228-3505

9A ST 200-71289B PL/IT 192-388410 MP BUCKET CYL.(OPT) 185-1839

11A LH 262-704911B RH 262-7050

268-9050(S)210-7076

13 STICK CYL. 210-7091(S)14 SWING CYL. 278-197115 BUCKET CYL. 210-7095(S)16 E-STICK CYL (OPT). 210-7097(S)

17A VALVE PILOT-BODY 223-471317B LEVER W/DTNT & SWTCH (OPT) 223-471518 ACCUMULATOR 226-042019 RIDE CNTRL VALVE (OPT) 245-878020 RIDE CNTRL ACCMLTR (OPT) 162-396021 RIDE CNTR PRES. SWTCH(OPT) 304-569622 TEMP. SENSOR (OPT) N/A23 DIFF. PRES. SWITCH (OPT) 134-040425 COUPLER VALVE (Volume 2) 231-261526 COUPLER CYLINDER (Volume 2) 190-3085

27 2 BANK 266-255227 3 BANK 266-2553

27A INLET SECTION 269-108027B LIFT SECTION 269-109127C TILT SECTION 269-109227D AUX SECTION 269-109327E OUTLET MANIFOLD 269-1079

28 3 BANK 266-256328B LIFT SECTION 269-108128C TILT SECTION 269-108228D AUX SECTION 269-1083

STEER CYLINDER

VALVE PILOT 2-BANK

LOADER VALVE (ST)

LOADER VALVE (PL/IT)

BOOM CYLINDER12

LIFT CYLINDERS

TILT CYLINDERS

STABILIZER CYLINDERS

Component Table

ITEM NAME PART NUMBER SCHEMATIC LOCATION

29 6 BANK 266-255629 7 BANK 266-255729 8 BANK 266-2558

29A BOOM SECTION 269-106229B SWING SECTION 269-106429C BUCKET SECTION 269-106529D STICK SECTION 269-106329G E-STICK SECTION 269-106629H RH STABILIZER SECTION 269-106129E AUX SECTION 269-106729F OUTLET MANIFOLD 269-105929J INLET MANIFOLD 269-106029K PATTERN SWITCHING VALVE 257-7724

29L LH STABILIZER SECTION 269-1061

30 VALVE GP - CUSHION RELIEF 206-3685 (STD)

31 VALVE GP - PILOT (BACKHOE) 267-2758

32 VALVE GP - PILOT (LOADER) 267-2758

33 MANIFOLD - PILOT 268-0094

BACKHOE VALVES (COMMON)

BACKHOE VALVE (CP)

Component Table Continued

Tap Description Schematic LocationT1 Pump DischargeT2 Load SenseT3 Pilot Pressure

SOS Oil Sampling

TAP LOCATIONS

Pressure Tap Table

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 RESTRICTIONVARIABLE and PRESSURE

COMPENSATED

PRESSURECOMPENSATION

PUMP: VARIABLE andPRESSURE COMPENSATED

ENERGY TRIANGLESHYDRAULIC PNEUMATIC

MEASUREMENT

PRESSURE TEMPERATURE FLOW

ROTATING SHAFTS

UNIDIRECTIONAL BIDIRECTIONAL

PUSH-PULL LEVER PEDALGENERAL MANUAL PUSH BUTTON SPRING

MANUAL CONTROL SYMBOLS

HYDRAULIC MOTORS

FIXEDDISPLACEMENT

VARIABLE DISPLACEMENTNON-COMPENSATED

UNIDIRECTIONAL

BIDIRECTIONAL

HYDRAULIC PUMPS

FLUID STORAGE RESERVOIRS

CROSSING AND JOINING LINES

VALVE ENVELOPES VALVE PORTS

BASIC COMPONENT SYMBOLS

FLUID CONDITIONERPUMP or MOTOR

FIXEDDISPLACEMENT

VARIABLE DISPLACEMENTNON-COMPENSATED

UNIDIRECTIONAL

BIDIRECTIONAL

VALVES

PILOT CONTROL SYMBOLSRELEASED PRESSURE

EXTERNAL RETURN INTERNAL RETURN

REMOTE SUPPLY PRESSURE

SIMPLIFIED COMPLETE INTERNALSUPPLY 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

BASICSYMBOL

SPRINGLOADED

CHECK VALVES

TWOPOSITION

INFINITEPOSITIONING

FLOW IN ONEDIRECTION

FLOW ALLOWED INEITHER DIRECTION

THREEPOSITION

CROSSFLOW

PARALLELFLOW

INTERNAL PASSAGEWAYS

NORMAL POSITION

A B

P T

A B

P TSHIFTED POSITION INFINITE POSITION

CONTROL VALVES

ATTACHMENT

MANUAL SHUTOFF

SHUTTLE PILOTCONTROLLED

FLUID POWER SYMBOLS

Hydraulic Symbols (Electrical)

325-AG135 PK-14

Circuit IdentificationNumber

Wire Color Wire Gauge

Harness identification codeThis example indicateswire 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 ColorCircuit Number Identification

B A

Wire

Wire

(EXAMPLE VALVE)

Current Standard

Transducer(Fluid)

Transducer(Gas / Air)

G

Generator

Electrical WirePressure Switch

MElectric Motor

Pressure Switch (Adjustable)

Temperature Switch

PressureSymbol

TemperatureSymbol

LevelSymbol

FlowSymbol

Electrical Symbols (Electrical)

T

ELECTRICAL SYMBOLS

LINE PATTERNS

Drain / Return Lines

Component Group

Pilot / Load Sensing Pressure

Pressure Line

Attachment

Air Line

CALLOUTS

Taps (Pressure, Sampling,Sensor) by letter

Components by number

YY

52

THIS SCHEMATIC IS FOR THE 420E BACKHOE LOADER (ST)VOLUME 1 of 2 PART NUMBER: 297-5426, CHANGE: 01, VERSION: -Components are shown installed on a fully operable machine.

Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.

DRAIN / RETURN LINE

HYDRAULIC CIRCUIT COLOR DESCRIPTIONSIMPLEMENT and STEERING PUMP CIRCUIT

SWING CYLINDER CIRCUIT

STEERING CYLINDER CIRCUIT

PILOT OIL CIRCUIT

BUCKET CYLINDER CIRCUIT

STICK CYLINDER CIRCUIT

LOAD SENSE CIRCUITSUPPLY LINE

AUXILIARY CIRCUIT (BACKHOE VALVE)E-STICK CYLINDER CIRCUIT

BOOM CYLINDER CIRCUITSTABILIZER CYLINDER CIRCUIT

BOOSTED BRAKE OIL CIRCUIT

LIFT CYLINDER CIRCUITTILT CYLINDER CIRCUITAUXILIARY CIRCUIT (LOADER VALVE)

12345678

A

B

C

D

E

F

12345678

A

B

C

D

E

F

STAB RH BOOM STICK SWING BUCKET E-STICK AUX. STAB LH

HMU

PUMP

TANK

BACKHOE VALVE

1

3

2

5

22

23

4

FRONT STEER CYL.

AUX

TILT

LIFT

LOADER VALVE

LEFT JOYSTICK RIGHT JOYSTICKSTABILIZER JOYSTICK

33

BOOSTED BRAKES (REF)

BS BT

LEFT BRAKEPEDAL

RIGHT BRAKEPEDAL

TO REAR AXLE LEFT WHEEL BRAKE

TO REAR AXLE RIGHT WHEEL BRAKE

DEL

27

T3

T2

T1

11B 12 13

14

3315 16

11A

29F29L29E29G29C29B

29K

29A29H29J

18

29

27A

27B

27C

27D

10

A8 A9

21

20

19

17C 17A 31 31

29D

SOS

6

27E

7

LINE PATTERNS

Drain / Return Lines

Component Group

Pilot / Load Sensing Pressure

Pressure Line

Attachment

Air Line

CALLOUTS

Taps (Pressure, Sampling,Sensor) by letter

Components by number

YY

52

THIS SCHEMATIC IS FOR THE 420E BACKHOE LOADER ( PL / IT )VOLUME 2 of 2 PART NUMBER: 297-5426, CHANGE: 01, VERSION: -Components are shown installed on a fully operable machine.

Refer to the appropriate Service Manual for Troubleshooting, Specifications and Systems Operations.

DRAIN / RETURN LINE

HYDRAULIC CIRCUIT COLOR DESCRIPTIONSIMPLEMENT and STEERING PUMP CIRCUIT

SWING CYLINDER CIRCUIT

STEERING CYLINDER CIRCUIT

PILOT OIL CIRCUIT

BUCKET CYLINDER CIRCUIT

STICK CYLINDER CIRCUIT

LOAD SENSE CIRCUITSUPPLY LINE

AUXILIARY CIRCUIT (BACKHOE VALVE)E-STICK CYLINDER CIRCUIT

BOOM CYLINDER CIRCUITSTABILIZER CYLINDER CIRCUIT

BOOSTED BRAKE OIL CIRCUIT

LIFT CYLINDER CIRCUITTILT CYLINDER CIRCUITAUXILIARY CIRCUIT (LOADER VALVE)

12345678

A

B

C

D

E

F

12345678

A

B

C

D

E

F

STAB RH BOOM STICK SWING BUCKET E-STICK AUX. STAB LH

HMU

PUMP

TANK

BACKHOE VALVE

11B 12 13

14

3315 16

11A

29F29L29E29G29C29B

29K

29A29H29J

6

1

3

2

5

22

23

4

18

FRONT STEER CYL.

29

AUX

TILT

LIFT

LOADER VALVE

LEFT JOYSTICK RIGHT JOYSTICKSTABILIZER JOYSTICK

33

3117C 17B 17A

BOOSTED BRAKES (REF)

BS BT

LEFT BRAKE PEDAL

RIGHT BRAKE PEDAL

TO REAR AXLE LEFT WHEEL BRAKE

TO REAR AXLE RIGHT WHEEL BRAKE

31

DEL

LOADER JOYSTICK

32

FLOAT RTD

T3

T2

T1

9B

10

26 25

8B

21

20

19

27A

28B

28C

28B

27E28

29D

SOS

7

15

16

13 12 31 33 5 6 3 2 8 4 9 10

26

25

101414 11B

11A

17 32 18

2930

28 1 19 20 8 7 9

Hydraulic Components - Chassis View

29F 29L 29C 29G 29C 29B 29D 29A 29H

29J

(29F) Outlet Manifold(29L) Left Stabilizer Control Valve(29E) Auxiliary Control Valve(29G) Extendable Stick Control Valve(29C) Bucket Control Valve(29B) Swing Control Valve(29D) Stick Control Valve

J

EIGHT BANK VALVE (PILOT OPERATED)

For other bank valve configurations see RENR6487 (Specifications Manual).

(29A) Boom Control Valve(29H) Right Stabilizer Control Valve(J) Pilot On/Off Solenoid Valve(29J) Inlet Manifold(L) A Ports(M) B Ports

L

M

Backhoe Valve (8 Bank)

C

B

H

E

G

C

A

D

D

T2

T1

T2

T2

T1

1

C

A

B

EF

These illustrations show the implement and steering pump (1) out of the machine. The following components are visible:

Torque control adjustment (A), Flow compensator adjustment (B), Load sensing pressure tap (T2), Inlet port (C), Case drain port (D), Torque control solenoid (E), Discharge pressure tap (T1), Torque limiter (F), Outlet port (G), Loader Valve (27).

The implement and steering pump on the 420E/430E machines are similar to the "D" Series machines, but now includes a torque control solenoid (not visible). The torque control solenoid provides an additional pump setting.

The implement and steering pump is located below the floor plate in the cab. The pump control valve (H) contains a torque control spool adjustment screw (B) and a flow compensator adjustment screw (A). The adjustment screws and the load sensing pres-sure tap (T2) are accessible from the cab.

Drain

27

Implement and Steering Pump

SOS

Filter Bypass Switch

The hydraulic oil filter is located below the machine at the left frame rail. The hydraulic oil filter bypass switch is mounted to the oil filter base.

Temp Sensor

Filter Bypass Switch

Temp Sensor

SOS

Hydraulic Oil Filter

HYDRAULIC OIL FILTER

SOS Filter Bypass Switch

5

The hydraulic oil filter is located below the machine at the left frame rail. The hydraulic oil filter bypass switch is mounted to the oil filter base.

SOS

Temp Sensor

Filter BypassSwitch

Temp Sensor

SOS

The loader valve is accessed from below the floor plate. The loader control valve group contains:

F

NOTE: Machines with a mechanically controlled loader valve or a pilot controlled loader valve use the same inlet manifold.

For other bank valve configurations see RENR6487 (Specifications Manual).

THREE BANK VALVE (PILOT OPERATED)

GH

J K L

M

P

R

N

(27E) Outlet manifold (27D, 28D) Auxiliary control valve (27C, 28C) Tilt control valve (27B, 28B) Lift control valve (27A) Inlet manifold (F) Load sensing relief valve (G) Solenoid for the B circuit (H) Solenoid for the A circuit (J) Makeup and relief valve (K) B pilot line port (L) A pilot line port (M) Priority Valve (N) Dead engine lower valve (P) A ports (R) B ports

27D27A

27C

27B

27

1

2827E

28D

28C 28B27A

Three Bank (Mechanically Controlled)

5

Loader Valve

Travel at high speeds over rough terrain causes bucket movement. The optional Ride Control System acts as a shock absorber by absorbing bucket forces, which stabilize the machine.

The Ride Control System components include; Ride Control Valve (19), Ride Control Relay, Ride Control Sole-noids, Ride Control Accumulator (20), and Ride Control Pressure Switch (21).

Two solenoids are now used on the "E" Series machines Ride Control System.

The Ride Control System, on machines with the optional autoshift transmission, is controlled by the Machine ECM. The Machine ECM monitors the position of the ride control switch and determines when to operate the ride control system.

21

ECM

Ride Control Relay

20

19

Ride Control (Option)

Ride Control Solenoids

The 420E/430E machines are equipped with hydraulically assisted master cylinders. The brake boost valves are connected to the master cylinder (A) at each brake pedal (B). Oil enters the master cylinder through the supply hose (C) and exits the master cylinder through the return hose (D). The oil flows to the service brakes through the hoses (E) at the bottom of the master cylinder. The master cylinders can be removed from the machine from inside the operator's compartment.

This illustration shows a sectional view of the boosted brake valve group. When the brake pedal is depressed, the boost brake valve moves to the left and inlet oil from the pilot manifold is directed to the master cylinder.

To Wheel Brake

Boost Brake Valve

From PilotAccumulatorTo Tank

Master Cylinder

SlaveCylinder

A BE D C

Boosted Brakes