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HELP CATERPILLAR ELPHINSTONE PTY. LTD.

R1700G LHD STIC

STEERING SYSTEM
MODULE
FORM NO. 9EP6156-00
FOR USE IN SERVICE TRAINING GUIDE:-
R1700G - JANUARY 2000

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

List of Contents
Caterpillar Elphinstone R1700G LHD
List of Contents ...........................................................................................................................................2
Important Safety Notice ..............................................................................................................................3
R1700G LHD STIC Steering System Overview .........................................................................................4
Introduction .................................................................................................................................................5
STIC Steering Component Location ............................................................................................................6
STIC Steering System Block Schematic ....................................................................................................7
STIC Steering Pilot System ........................................................................................................................8
Neutralizer Valves ..................................................................................................................................... 11
Main Steering System Components .......................................................................................................... 12
Main Control Valve (Hold Position) ............................................................................................................13
Main Control Valve (Right Turn) .................................................................................................................14
STIC Steering System (Hold) ...................................................................................................................16
STIC Steering System (Gradual Right Turn) .............................................................................................17
STIC Steering System (Full Right Turn) ....................................................................................................18
Secondary Steering System Components (If Equipped) ..........................................................................19
Secondary Steering Sectional Schematic (If Equipped) ........................................................................... 20
Secondary Steering System (Engine Below 2000 rpm) ............................................................................21
Secondary Steering System (Engine Above 2000 rpm) ........................................................................... 22
Secondary Steering System (Engine Off) ................................................................................................. 23
Check The System (Practical Task) .......................................................................................................... 24

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

IMPORTANT SAFETY NOTICE

The course content and subject matter is current
at the time of publication. Specifications,
torques, pressure settings, measurements,
adjustments, illustrations and other items can
change at any time. Always refer to the machine
specific service manual, parts book and updates
prior to performing repairs and adjustments.
Caterpillar Elphinstone Pty Ltd cannot anticipate
every possible circumstance that might involve
a potential hazard. The warnings in this module
are therefore not inclusive. If a procedure, tool,
device or work method not specifically
recommended by Caterpillar Elphinstone Pty Ltd
is to be used, you must satisfy yourself that it is
safe for yourself and others. You should also
ensure that the machine will not be damaged or
made unsafe by the procedures you choose.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

R1700G LHD STIC Steering System Overview

Module Description

Aims:
The aim of this training module is to provide participants with the operational knowledge and diagnostic skills necessary to
troubleshoot the R1700G LHD STIC Steering System.

Nominal Duration:
The module is designed so that most of the trainees will acquire the knowledge in one 4 hour session. The length of time
actually taken to complete the module will vary depending on factors such as the teaching method used, the trainee’s
knowledge and skills at entry, and the individual trainee’s ability.

Pre-Requisites:
Mechanical tradesman - should have completed a Basic Hydraulic Training Program (preferred but not essential).

Learning Outcomes:
As a result of studying this module, participants should be able to:
1. Demonstrate an understanding of the function and operation of the STIC Steering system and its components.
2. Use and understand the STIC Steering system schematic.
3. Trace the oil flow through the STIC steering system during all modes of operation.
4. Apply this operational knowledge to troubleshoot a series of STIC Steering system problems.
5. Use the Service Manual and Parts Book to assist with troubleshooting.

Assessment:
Tasks:
Part A: Practical Tests
Part B: Theory Assessment (Multiple Choice Test)

Resource Requirements:
• R1700G LHD.
• Fully equipped classroom with white board and overhead projector.
• Training Module and handout material.
• Hydraulic pressure gauges.
• Service Manual.
• Parts Book.
• Tools for practical tasks.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

Introduction

• Introduction: This presentation discusses the system operation and adjusting

procedures for the R1700G STIC Steering System.

Graphical symbols and sectional view drawings will be used when

discussing systems operations. Systems will be explained by tracing oil
flow from the tank, through the system, and back to the tank.

• Schematic colour code: The colour codes for hydraulic oil used throughout this presentation
are as follows:
Red - System or High Pressure.
Orange - Pilot Pressure.
Blue - Blocked or Trapped Oil.
Green - Tank or Return Oil.

• Testing & Adjusting NOTE: Always follow the procedures in the Service Manual
procedures: when testing and/or adjusting the machine.

• Serviceman’s Handouts: Give each trainee a copy of the relevant serviceman’s handouts,
supplied with this training module.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

1 2 3 4 5 6 7

8 9 10 11 12

STIC Steering Component Location

• Steering system components: The steering hydraulic system is made up of two basic circuits, the
(1) Steering secondary pilot circuit and the main steering circuit. When the machine is
lockout valve equipped with the optional secondary steering attachments or the
(2) STIC pilot control reversible steering attachments, the steering system also includes
valve these additional circuits.
(3) Neutralizer valves
(4) Main control valve The main components of the pilot circuit are hydraulic oil tank (9),
(5) Dual pilot check valve brake and pilot pump (11), pilot pressure reducing valve (6), steering
(6) Pilot pressure reducing secondary lockout valve (1), STIC pilot control valve (2), dual pilot
valve check valve (5), neutralizer valves (3) and selector and pressure
(7) Oil cooler control valve (10).
(8) Steering cylinders
(9) Hydraulic oil tank The primary components of the main steering circuit are hydraulic oil
(10) Selector and pressure tank (9), steering pump (12), main control valve (4), steering
control valve cylinders (8) and oil cooler (7).
(11) Brake and pilot pump
(12) Steering pump

§SH-Page 22

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

TO IMPLEMENT
PILOT SYSTEM

STIC PILOT
PILOT PRESSURE CONTROL VALVE
SELECTOR AND
REDUCING VALVE
PRESSURE CONTROL
VALVE

STEERING DUAL PILOT

SECONDARY CHECK VALVE
NEUTRALIZER
LOCKOUT
VALVE
VALVE

TO BRAKE NEUTRALIZER
SYSTEM VALVE

MAIN
CONTROL VALVE

BRAKE AND STEERING STEERING

PILOT PUMP PUMP CYLINDERS

FILTER OIL COOLER

TANK

STIC Steering System Block Schematic

• Pilot system consists of: This block diagram of the R1700G STIC steering system shows the
- Brake and pilot pump components and oil flow. The steering pilot circuit consists of the
- Pilot pressure reducing brake and pilot pump, pilot pressure reducing valve, selector and
valve pressure control valve, STIC pilot control valve, steering secondary
- Selector and pressure lockout valve, dual pilot check valve and two neutralizer valves.
control valve When the steer lever is moved to the right or left, pilot oil is sent
- STIC pilot control valve through the respective neutralizer valve to the directional control
- Steering secondary lockout spool in the main control valve. The pilot oil moves the directional
valve control spool and allows steering pump oil to flow to the steering
- Dual pilot check valve cylinders.
- Two neutralizer valves
The main steering circuit consists of the steering pump, main control
• Main system consists of: valve and steering cylinders. The steering pump draws oil (green)
- Steering pump from the tank and sends oil flow (red) to the main control valve.
- Main control valve
- Steering cylinders The main control valve houses the combination valve and the
directional control spool. In the hold position the oil (blue) to the
steering cylinders is blocked. The steering cylinders are fitted with
line relief valves to protect them from external shocks.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

1. Brake and pilot pump. 2. Pilot pressure reducing valve.

3
4

3. Selector and pressure control valve. 4. Hydraulic oil tank.

4

STIC Steering Pilot System

• The brake and pilot pump is The brake and pilot pump (1) is part of a two section gear type
part of a two section gear pump mounted on the torque converter updrive housing. The brake
type pump and pilot pump (1) supplies oil to the parking brake circuit, service
brake circuit, implement pilot circuit and the STIC steering pilot
• The brake and pilot pump circuit. The rear section of the pump supplies oil to the main
supplies oil to the: steering system.
- Implement pilot circuit
- Parking brake circuit Oil flows from brake and pilot pump (1) to pilot pressure reducing
- Service brake circuit valve (2). The pilot pressure reducing valve (2) maintains a constant
- Steering pilot circuit pressure in the pilot oil circuits. Oil flows from pilot pressure
reducing valve (2) to selector and pressure control valve (3). The
• The pressure reducing valve selector and pressure control valve (3) blocks the flow of alternate
limits the maximum oil pilot oil into the into the pilot system. But if the brake and pilot pump
pressure in the pilot system fails, or oil is not available, then the selector and pressure control
valve (3) will allow alternate pilot oil to flow into the pilot system from
• The selector and pressure either the lift cylinders or the main control valve.
control valve will supply
alternate oil to the pilot The hydraulic oil tank (4) is located on the right hand side of the
system machine and supplies oil to the brake and pilot pump and steering
pump. The hydraulic return filters are mounted inside the hydraulic
oil tank.
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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

1
2

1. STIC pilot control valve. 2. Primary transmission and steering lockout lever.

4 3

5
3. Neutralizer valve.
4. Striker. 5. Steering Secondary Lockout Valve.
5

STIC Steering Pilot System

• The STIC pilot control valve The STIC pilot control valve (1) is mounted on the operator station
sends pilot oil to the door. The STIC pilot control valve (1) sends pilot oil to the main
directional control spool in control valve to move the directional control spool to turn the
the main control valve machine left or right.

• The primary steering and The primary steering and transmission lockout lever (2) is used to
transmission lockout lever mechanically lock the STIC pilot control valve in the neutral position
mechanically locks the STIC when the operator is leaving the cab.
pilot control valve
The two neutralizer valves (3) are mounted on the rear frame. Each
• At the end of a turn the neutralizer valve has an adjustable striker (4) mounted on the front
striker moves the neutralizer frame. When the machine makes a maximum turn (either left or
valve spool stopping pilot oil right) the respective striker will contact the neutralizer valve at the
flow to the control valve end of the turn. The striker moves the neutralizer valve spool and
spool blocks pilot oil flow to the directional spool in the main control valve.
With the oil flow stopped, the directional control spool centering
• Centering spring centers the spring centers the spool and stops the machine from turning before
spool and stops the turn the machine turns against the frame stops.
Continued

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

• The secondary steering The secondary steering lockout valve (5) is mounted on the inside of
lockout valve when activated the operators station door. When the operators station door is
blocks pilot oil supply to the opened, the valve is activated blocking the pilot oil supply to the
STIC pilot control valve STIC pilot control valve, this stops the steering action while an
operator is mounting or dismounting the machine.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

LESS THAN MAXIMUM TURN

TO FROM
MAIN STIC PILOT
CONTROL CONTROL VALVE
VALVE
ORIFICE SPRING

TO TANK

MAXIMUM TURN
TO FROM
VALVE SPOOL CENTER PASSAGE MAIN STIC PILOT
CONTROL CONTROL VALVE
VALVE
ORIFICE SPRING

TO TANK

VALVE SPOOL CENTER PASSAGE

Neutralizer Valves

• Sectional view of neutralizer Shown is a sectional view of the neutralizer valve. During less than
valve maximum articulation, pilot oil from the STIC pilot control valve flows
through the neutralizer valve to the main control valve.
• Striker moves the neutralizer
valve spool blocking pilot oil When the striker moves the neutralizer valve spool, pilot oil flow to
supply to the main control the main directional control spool is blocked. Pilot oil at the
valve directional control spool flows back through the orifice of the center
passage in the neutraliser spool to drain. The centering spring on
• Pilot oil at the main control the directional control spool centers the spool in the main control
valve drains to the hydraulic valve and stops the machine from turning.
oil tank through the
neutralizer valve spool

§SH-Page 23

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

1. Steering pump.
1 2. Main control valve.

3 4

3. Steering cylinder. 4. Oil cooler.

7

Main Steering System Components

• The steering pump is part of The steering pump (1) is the rear section of the two section gear type
the two section gear type pump mounted on the torque converter updrive housing. The
pump mounted on the torque steering pump is a fixed displacement pump which supplies oil to
converter updrive housing the main control valve.

• The main control valve Main control valve (2) is located in the rear frame, immediately to the
contains the combination rear of the articulation hitch. The main control valve houses the
valve and the directional combination valve and the directional control spool. The main
control spool control valve sends oil to the steering cylinders.

• The steering cylinders are Steering cylinders (3) are located on either side of the lower
located either side of the articulation hitch. The steering cylinders have crossline relief valves
lower articulation hitch mounted on them which protect the cylinders from large external
forces overloading the cylinder.
• The oil cooler is hinge
mounted on the rear of the The oil cooler (4) is hinge mounted on the outside of the radiator and
radiator can be swung out for servicing. Access is gained by opening the
guard at the rear of the machine. The oil cooler is air cooled by the
engine fan and cools the return steering oil.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

Main Control Valve (Hold Position)

• Main control valve in the hold This sectional view of the main control valve identifies the various
position components. The control valve is in the hold position.

• Steering pump oil is blocked When oil from the steering pump enters the main control valve, the
by the control spool, oil is blocked by the control spool and the combination dump, flow
combination dump, flow and and relief valve. The function of the control spool is to direct oil to
relief valve the respective ends of the steering cylinders when making a turn.
The function of the combination valve depends on the operational
• The control spool directs oil mode of the steering system.
to the respective ends of the
steering cylinders when When in the hold position, leakage around the control spool allows
making a turn pressure in the lines to the steering cylinders to bleed to the
hydraulic oil tank. Oil behind the combination valve is connected
• The combination valve acts through the spring chamber oil passage to the control spool and the
as a dump valve lines to the steering cylinders. Pump oil flow entering the main
control valve is blocked by the combination valve and the control
spool. The supply pressure increases until the pressure exceeds
the force of the combination valve spring. The valve compresses the
§SH-Page 24 springs and sends the pump oil flow to the hydraulic oil tank. Oil in
the valve spring chamber flows back through the spring chamber oil
passage to the control spool. The combination valve acts as a
dump valve. Page 13
 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

Main Control Valve (Right Turn)

• Pilot oil moves the spool in When the STIC pilot control valve is moved to the right, pilot oil
the main control valve moves the spool in the main control valve to the left. Movement of
opening a variable orifice the spool opens a variable orifice. Oil flow through the orifice
generates a pressure difference between the oil in the left end of the
• Oil flow through the orifice combination valve (higher pressure) and the oil to the steering
generates a pressure cylinders (lower pressure). Oil also flows to the steering cylinders
difference through the pilot passage to the shuttle valve. The shuttle valve
moves up and blocks the flow of oil to the return side of the spool.
• Oil flow to the steering Oil flow continues through the spring chamber oil passage and the
cylinders also flows to the orifice to the spring chamber behind the combination valve.
shuttle valve which moves
and blocks oil flow to the The oil in the spring chamber behind the combination valve is the
return side of the spool same pressure as the oil in the steering cylinders. The oil pressure
plus the spring force moves the combination valve to the left towards
• Combination valve acts as a the closed position. Movement of the valve restricts some of the oil
flow control valve flow to the hydraulic oil tank and sends more oil to the steering
cylinders. Therefore the combination valve acts as a flow control
valve
Continued

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

• When external forces prevent When external forces prevent the machine from turning, the steering
the machine from turning, the cylinders are blocked. Continued displacement of the STIC pilot
oil in the cylinders is blocked control valve sends pilot oil to keep the spool in the main control
valve in the open position. The steering pump oil flow is blocked at
• Pilot oil from the STIC pilot the cylinders. Oil ceases to flow through the orifice at the spool.
control valve keeps the main System oil pressure becomes equal. The oil pressure in the front of
control valve spool in the the flow control valve equals the oil pressure in the spring chamber
open position behind the flow control valve. The spring moves the flow control
valve to the left and stops all oil flow to the hydraulic oil tank.
• Steering pump oil flow is System oil pressure increases to the relief valve setting. The pilot
blocked at the steering valve opens and sends oil in the spring chamber to the hydraulic oil
cylinders, oil flow through the tank. Oil flow through the orifice causes the oil pressure at the left
orifice at the spool stops end of the flow control valve to be higher than the oil pressure in the
spring chamber. The higher oil pressure opens the valve. Steering
• System pressure equalizes, pump oil flows through the open valve to the hydraulic oil tank. The
the spring moves the flow combination valve now functions as a relief valve.
control valve and stops oil
flow to the hydraulic oil tank

• The combination valve now

acts as a relief valve

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

STEERING
CYLINDERS

CROSSLINE CROSSLINE
RELIEF VALVE RELIEF VALVE

DOUBLE
CHECK
VALVE

MAIN
CONTROL
VALVE
COMBINATION
VALVE

OIL COOLER

LEFT RIGHT
NEUTRALIZER NEUTRALIZER
STIC
CONTROL
VALVE PILOT PRESSURE
REDUCING VALVE

DUAL PILOT
CHECK VALVE

SECONDARY
FROM LIFT LOCKOUT VALVE
CYLINDERS

BRAKE AND
STEERING PILOT PUMP
PUMP

HYDRAULIC OIL TANK

SELECTOR AND PRESSURE
CONTROL VALVE

10

STIC Steering System (Hold)

• Pilot pressure reducing valve With the engine running oil from the brake and pilot pump flows to
maintains a constant the pilot pressure reducing valve. The pilot pressure reducing valve
pressure in the pilot circuits maintains a constant oil pressure in the pilot circuits. The brake and
pilot pump also supplies oil to the brake system and the implement
• The brake and pilot pump pilot circuit.
also supplies oil to the brake
system and the implement Pilot oil from the pilot pressure reducing valve flows through the
pilot circuit secondary steering lockout valve to the STIC pilot control valve.
When the operators station door is open the secondary steering
• Secondary steering lockout lockout valve blocks the pilot oil supply to the STIC pilot control
valve blocks pilot oil supply valve.
to the STIC pilot control valve
when the operators station When the STIC pilot control valve is in the neutral position pilot oil
door is open supply to the main control valve is blocked by the valve. The
steering pump supplies oil to the main control valve. With the main
• The combination valve in the control valve in the hold position the combination valve located in the
main control valve acts as a main control valve acts as a dump valve and returns the steering
dump valve pump oil through the oil cooler to the hydraulic oil tank.
§ SH-Page 25

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

STEERING
CYLINDERS

CROSSLINE CROSSLINE
RELIEF VALVE RELIEF VALVE

DOUBLE
CHECK
VALVE

MAIN
CONTROL
VALVE
COMBINATION
VALVE

OIL COOLER

LEFT RIGHT
NEUTRALIZER NEUTRALIZER
STIC
CONTROL
VALVE PILOT PRESSURE
REDUCING VALVE

DUAL PILOT
CHECK VALVE

FROM LIFT
SECONDARY
LOCKOUT VALVE
CYLINDERS

BRAKE AND
STEERING PILOT PUMP
PUMP

HYDRAULIC OIL TANK

SELECTOR AND PRESSURE
CONTROL VALVE

11

STIC Steering System (Gradual Right Turn)

• STIC pilot control valve When the STIC pilot control valve is moved to the right turn position
moved to the right turn the valve directs pilot oil through the right hand neutralizer valve to
position and pilot oil acts on the main control valve. The pilot oil acts on the right hand side of the
the right side of the spool in spool in the main control valve moving it to the left. Pilot oil on the
the main control valve left hand side of the spool returns to the hydraulic oil tank through
moving it to the left the left hand side neutralizer valve and the STIC pilot control valve.

• When the spool moves to the When the spool in the main control valve moves to the left it allows
left steering pump oil is oil from the steering pump to flow to the head end of the left steering
directed to the head end of cylinder and the rod end of the right steering cylinder. The machine
the left steering cylinder and then turns to the right. The oil in the rod end of the left cylinder and
the rod end of the right the head end of the right cylinder returns to the hydraulic oil tank
steering cylinder, the machine through the main control valve and oil cooler.
turns to the right

§ SH-Page 26

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

STEERING
CYLINDERS

CROSSLINE CROSSLINE
RELIEF VALVE RELIEF VALVE

DOUBLE
CHECK
VALVE

MAIN
CONTROL
VALVE
COMBINATION
VALVE

OIL COOLER

LEFT RIGHT
NEUTRALIZER NEUTRALIZER
STIC
CONTROL
VALVE PILOT PRESSURE
REDUCING VALVE

DUAL PILOT
CHECK VALVE

SECONDARY
FROM LIFT LOCKOUT VALVE
CYLINDERS

BRAKE AND
STEERING PILOT PUMP
PUMP

HYDRAULIC OIL TANK

SELECTOR AND PRESSURE
CONTROL VALVE

12

STIC Steering System (Full Right Turn)

• STIC pilot control valve in the When the STIC pilot control valve is in the right turn position and the
right turn position striker has machine has turned as far right as it can turn the striker contacts the
contacted the right right neutralizer valve. Pilot oil flow from the STIC pilot control valve
neutralizer valve moving the to the spool in the main control valve is blocked by the movement of
valve the neutralizer valve. When the flow of pilot oil stops acting on the
spool centering springs will return the spool to the hold position and
• Pilot oil flow to the spool in the steering action of the machine stops.
the main control valve is
blocked by the neutralizer The neutralizer valves prevent the front frame from contacting the
and the spool returns to the rear frame of the machine when turning full left or full right
hold position
Notice
Check the Service Manual for the correct adjusting procedure.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

1. Secondary steering pump.

2. Secondary steering diverter valve.

13

Secondary Steering System Components (If Equipped)

• The secondary steering pump The secondary steering pump (1) is a gear type pump mounted on
is a ground driven gear type the front of the transmission and attached to the transmission output
pump gears. It is a ground driven pump that rotates as long as the
machine is moving.
• The secondary steering
system has three purposes The secondary steering system has three purposes:
(a) To provide steering supply oil should the main steering pump fail
• The secondary steering while the machine is moving.
diverter valve contains two (b) To supply oil if the engine should stop while the machine is
check valves and two spool moving.
valves which control the oil (c) Add oil to the main steering pump output when the engine
flow from the secondary speed is below 2000 rpm and the machine is moving.
steering pump
The secondary steering diverter valve (2) is mounted on the right
side of the transmission. Two check valves and two spool valves
are housed within the diverter valve which directs the secondary
steering pump oil flow depending on the machines operational
requirements.

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

BRAKE/ STEERING
PILOT PUMP
PUMP

DIVERTER SPOOL

CHECK VALVE
MAIN
CONTROL
VALVE

ORIFICE

CHECK
VALVE

STEERING
CYLINDERS

SECONDARY STEERING
FILTER REVERSING
DIVERTER VALVE
VALVE

SECONDARY
STEERING PUMP
HYDRAULIC OIL TANK
14

Secondary Steering Sectional Schematic (If Equipped)

• Secondary steering Shown is a sectional schematic of the machine steering system with
attachment consists of the optional secondary steering attachment. The secondary steering
secondary pump and diverter pump is splined to the transmission output transfer gear. When the
valve machine moves, the transfer gear turns the pump. The secondary
steering attachment consists of the secondary pump and diverter
• Pump is splined to the valve.
transmission output transfer
gear The diverter valve consists of a reversing spool, two check valves, a
diverter spool and an orifice (to the left of the upper check valve).
• Diverter valve:
- Reversing spool
- Two check valves
- Diverter spool
- Orifice

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

STEERING
CYLINDERS

CROSSLINE CROSSLINE
RELIEF VALVE RELIEF VALVE

SECONDARY DOUBLE
STEERING PUMP CHECK
REVERSING VALVE
SPOOL

MAIN
CONTROL
VALVE
CHECK COMBINATION
VALVES VALVE

OIL COOLER
DIVERTER
SPOOL

ORIFICE

SECONDARY LEFT RIGHT

STEERING NEUTRALIZER NEUTRALIZER
DIVERTER VALVE
STIC
CONTROL
VALVE PILOT PRESSURE
REDUCING VALVE

DUAL PILOT
CHECK VALVE

SECONDARY
LOCKOUT VALVE

BRAKE AND
TO SELECTOR STEERING PILOT PUMP
AND PRESSURE PUMP
CONTROL VALVE

HYDRAULIC OIL TANK

15

Secondary Steering System (Engine Below 2000 rpm)

• Machine moving, engine When the machine is moving and engine speed is less than 2000
speed below 2000 rpm rpm, pressure caused by the steering pump oil flow through the
orifice (located in the secondary steering diverter valve) is not high
• Low steering pump oil flow enough to move the diverter spool. Oil in the secondary pump
through the orifice supply passage is blocked from the hydraulic oil tank. The check
valve opens and secondary pump oil joins the oil from the steering
• Diverter spool closed to the pump to supply the steering system.
hydraulic oil tank

• Secondary pump oil

supplements steering pump
oil

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

STEERING
CYLINDERS

CROSSLINE CROSSLINE
RELIEF VALVE RELIEF VALVE

SECONDARY DOUBLE
STEERING PUMP CHECK
REVERSING VALVE
SPOOL

MAIN
CONTROL
VALVE
CHECK COMBINATION
VALVES VALVE

OIL COOLER
DIVERTER
SPOOL

ORIFICE

SECONDARY LEFT RIGHT

STEERING NEUTRALIZER NEUTRALIZER
DIVERTER VALVE
STIC
CONTROL
VALVE PILOT PRESSURE
REDUCING VALVE

DUAL PILOT
CHECK VALVE

SECONDARY
LOCKOUT VALVE

BRAKE AND
TO SELECTOR STEERING PILOT PUMP
AND PRESSURE PUMP
CONTROL VALVE

HYDRAULIC OIL TANK

16

Secondary Steering System (Engine Above 2000 rpm)

• Machine moving, engine When the machine is moving and the engine speed is higher than
speed above 2000 rpm 2000 rpm) the increase in steering pump oil flow through the orifice
(located in the secondary steering diverter valve) increases the
• Steering pump flow through pressure of oil upstream of the orifice. The increase in oil pressure
the orifice increases moves the diverter spool to the open position. Oil in the secondary
supply passage is sent to the hydraulic oil tank. The check valve
• Diverter spool opens, closes preventing steering pump oil from going through the diverter
secondary pump oil sent to valve to the hydraulic oil tank. When engine speed is above 2000
the hydraulic oil tank rpm) the steering pump supplies all the oil used in the steering
system.
• Check valve blocks steering
pump oil from the hydraulic
oil tank, steering pump
supplies all oil used

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

STEERING
CYLINDERS

CROSSLINE CROSSLINE
RELIEF VALVE RELIEF VALVE

SECONDARY DOUBLE
STEERING PUMP CHECK
REVERSING VALVE
SPOOL

MAIN
CONTROL
VALVE
CHECK COMBINATION
VALVES VALVE

OIL COOLER
DIVERTER
SPOOL

ORIFICE

SECONDARY LEFT RIGHT

STEERING NEUTRALIZER NEUTRALIZER
DIVERTER VALVE
STIC
CONTROL
VALVE PILOT PRESSURE
REDUCING VALVE

DUAL PILOT
CHECK VALVE

SECONDARY
LOCKOUT VALVE

BRAKE AND
TO SELECTOR STEERING PILOT PUMP
AND PRESSURE PUMP
CONTROL VALVE

HYDRAULIC OIL TANK

17

Secondary Steering System (Engine Off)

• Machine moving engine off If the machine is moving with the engine off, no oil flows through the
orifice (located in the secondary steering diverter valve). The
• Secondary pump supplies oil secondary pump draws oil from the hydraulic oil tank. Supply oil is
sent through an internal passage in the reversing spool to the end of
• Diverter spool blocks flow to the spool. Pressure oil moves the reversing spool and connects the
the hydraulic oil tank pump supply oil to an internal passage, the upper check valve and
the diverter spool. The spring in the diverter spool holds the diverter
• Secondary oil supplies the spool in the closed position. Oil flow unseats the upper check valve,
steering system seats the lower check valve and fills the steering system

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 Service Training Module
STIC Steering System
CATERPILLAR ELPHINSTONE PTY. LTD.

18

Check The System

(Practical Task)

Explain tasks: Each trainee will be required to successfully complete the tasks
listed below.
1 . Setting the main steering relief valve.
2 . Adjust the neutralizer stops.

Practical Test Guidelines

1. The trainee must find the procedure in the Service Manual.
2. The trainee must follow the procedure and successfully complete
the task.

Service Manual: Always check the Service Manual for the correct adjusting procedure
and specifications.

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