Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1093

POWER-ASSISTED STEERING SYSTEM

2A–9

The hydraulic pump is vane-type design. The 
submerged pump has housing and internal parts that 
are inside the reservoir and operate submerged in oil. 
There are two bore openings at the rear of the pump 
housing. The larger opening contains the cam ring, 
pressure plate, thrust plate, rotor and vane assembly, 
and end plate. The smaller opening contains the 
pressure line union, flow control valve and spring.
The flow control orifice is part of the pressure line union. 
The pressure relief valve inside the flow control valve 
limits the pump pressure.

Pressure Switch

When hydraulic pressure reaches 3430 kPa (500 psi), 
the pressure switch of the power steering pump closes 
causing the Powertrain Control Module (PCM) to 
actuate the throttle valve, which increases the engine 
rpm to prevent the overload-induced engine speed slow 
down. The switch opens when hydraulic pressure drops 
to 2940 kPa (430 psi).

Steering Column

431RY00004

WARNING:  TO AVOID DEPLOYMENT WHEN 
TROUBLE-SHOOTING THE SRS SYSTEM, DO NOT 
USE ELECTRICAL TEST EQUIPMENT, SUCH AS 
BATTERY-POWERED OR A/C-POWERED 
VOLT-METER, OHMMETER, ETC., OR ANY TYPE OF 
ELECTRICA L EQUIPMENT OTHER THAN 
SPECIFIED IN THIS MANUAL. DO NOT USE A 
NON-POWERED PROBE-TYPE TESTER.

INSTRUCTION IN THIS MANUAL MUST BE 
FOLLOWED CAREFULLY, OTHERWISE PERSONAL 
INJURY MAY RESULT.
When servicing a vehicle equipped with Supplemental 
Restraint System, pay close attention to all WARNINGS 
and CAUTIONS.
For detailed explanation about SRS, refer to Restraints 
section.

2A–10

POWER-ASSISTED STEERING SYSTEM

The steering column has three important features in 
addition to the steering function:

1. The column is energy absorbing, designed to 

compress in a front-end collision to minimize the 
possibility of injury to the driver of the vehicle.

2. The ignition switch and lock are mounted 

conveniently on the column.

3. With the column mounted lock, the ignition and 

steering operation can be locked to prevent theft of 
the vehicle.

The column can be disassembled and reassembled. 
However, to insure the energy absorbing action, use 
only the specified screws, bolts and nuts as designated, 
and tighten them to the specified torque.
Handle the column with care when it is removed from 
the vehicle. A sharp blow on the end of steering shaft or 
shift lever, or dropping the assembly could shear or 
loosen the fasteners that maintain column rigidity.

Power Steering System Test

Test Procedure

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E nd O FCallo ut

Test of fluid pressure in the power steering system is 
performed to determine whether or not the oil pump and 
power steering unit are functioning normally.
The power steering system test is used to identify and 
isolate hydraulic circuit difficulties. Prior to performing 
this test, the following inspections and corrections, if 
necessary, must be made.

• Inspect pump reservoir for proper fluid level.

• Inspect pump belt for proper tension.

• Inspect pump driver pulley condition. 

1. Place a container under the pump to catch the fluid 

when disconnecting or connecting the hoses.

2. With the engine NOT running, disconnect the 

pressure hose at the power steering pump and 
install power steering tester J-29877-A. The gage 
must be between the shutoff valve and pump. Open 
the shutoff valve.

3. Check the fluid level. Fill the reservoir with power 

steering fluid, to the “Full" mark. Start the engine, 
then turn the steering wheel and momentarily hold it 
against a stop (right or left). Turn the engine off and 
check the connections at tester for leakage.

Legend

(1)

Fluid Reservoir

(2)

Power Steering Unit

(3)

Power Steering Pump

POWER-ASSISTED STEERING SYSTEM

2A–11

4. Bleed the system. Refer to Bleeding the Power 

Steering System in this section.

5. Start the engine and check the fluid level. Add 

power steering fluid if required. When the engine is 
at normal operating temperature, increase engine 
speed to 1500 rpm.

CAUTION:  Do not leave shutoff valve fully closed 
for more than 5 seconds, as the pump could 
become damaged internally.

6. Fully close the shutoff valve. Record the highest 

pressures.

• If the pressure recorded is within 9300–9800 kPa 

(1350–1420 psi), the pump is functioning within 
its specifications.

• If the pressure recorded is higher than 9800 kPa 

(1420 psi), the valve in the pump is defective.

• If the pressure recorded is lower than 9300 kPa 

(1350 psi), the valve or the rotating group in the 
pump is defective.

7. If the pump pressures are within specifications, 

leave the valve open and turn (or have someone 
else turn) the steering wheel fully in both directions. 
Record the highest pressures and compare with the 
maximum pump pressure recorded in step 6. If this 
pressure cannot be built in either side of the power 
steering unit, the power steering unit is leaking 
internally and must be replaced.

8. Shut the engine off, remove the testing gauge. 

9. Reconnect the pressure hose, check the fluid level 

and make the needed repairs.

10. If the problem still exists, the steering and front 

suspension must be thoroughly examined.

Maintenance

The hydraulic system should be kept clean and fluid 
level in the reservoir should be checked at regular 
intervals and fluid added when required. Refer to 
Recommended Fluids and Lubricants in General 
Information section for the type of fluid to be used and 
the intervals for filling.
If the system contains some dirt, flush it as described in 
this section. If it is exceptionally dirty, the pump must be 
completely disassembled before further usage. (The 
steering unit cannot be disassembled.)
All tubes, hoses, and fittings should be inspected for 
leakage at regular intervals. Fittings must be tight. Make 
sure the clips, clamps and supporting tubes and hoses 
are in place and properly secured.
Power steering hoses and lines must not be twisted, 
kinked or tightly bent. Air in the system will cause 
spongy action and noisy operation. When a hose is 
disconnected or when fluid is lost, for any reason, the 
system must be bled after refilling. Refer to Bleeding the 
Power Steering System in this section.

• Inspect belt for tightness.

• Inspect pulley for looseness or damage. The pulley 

should not wobble with the engine running.

• Inspect hoses so they are not touching any other 

parts of the vehicle.

• Inspect fluid level and fill to the proper level. 

Fluid Level

1. Run the engine until the power steering fluid 

reaches normal operating temperature, about 55

°C 

(130

°F), then shut the engine off.

2. Check the level of fluid in the reservoir.

3. If the fluid level is low, add power steering fluid as 

specified in General Information to the proper level 
and install the receiver cap.

4. When checking the fluid level after the steering 

system has been serviced, air must be bled from the 
system. Refer to Bleeding the Power Steering 
System in this section.

Bleeding The Power Steering System

When a power steering pump or unit has been installed, 
or an oil line has been disconnected, the air that has 
entered the system must be bled out before the vehicle 
is operated. If air is allowed to remain in the power 
steering fluid system, noisy and unsatisfactory 
operation of the system may result. 

Bleeding Procedure

When bleeding the system, and any time fluid is added 
to the power steering system, be sure to use only power 
steering fluid as specified in General Information.

1. Fill the pump fluid reservoir to the proper level and 

let the fluid settle for at least two minutes.

2. Start the engine and let it run for a few seconds. Do 

not turn the steering wheel. Then turn the engine off.

3. Add fluid if necessary.

4. Repeat the above procedure until the fluid level 

remains constant after running the engine.

5. Raise and support the front end of the vehicle so 

that the wheels are off the ground.

6. Start the engine. Slowly turn the steering wheel right 

and left, lightly contacting the wheel stops.

7. Add power steering fluid if necessary.

8. Lower the vehicle, set the steering wheel at the 

straight forward position after turning it to its full 
steer positions 2 or 3 times, and stop the engine.

9. Check the fluid level and refill as required.

10. If the fluid is extremely foamy, allow the vehicle to 

set a few minutes, then repeat the above procedure. 

Flushing The Power Steering System

1. Raise and support the front end of the vehicle off the 

ground until the wheels are free to turn.

2. Remove the fluid return line at the pump inlet 

connector and plug the connector port on the pump.
Position the line toward a large container to catch 
the draining fluid.

3. While running the engine at idle, fill the reservoir 

with new power steering fluid. Turn the steering 
wheel in both directions. Do not contact or hold the 
steering wheel to the wheel stops. This will cause 
the pump to go to pressure relief mode, which may 
cause a sudden fluid overflow at the reservoir.

2A–12

POWER-ASSISTED STEERING SYSTEM

4. Install all the lines and hoses. Fill the system with 

new power steering fluid and bleed the system as 
described in Bleeding The Power Steering System. 
Operate the engine for about 15 minutes.
Remove the pump return line at the pump inlet and 
plug the connection on the pump. While refilling the 
reservoir, check the draining fluid for contamination. 
If foreign material is still evident, replace all lines, 
disassemble and clean or replace the power 
steering system components. Do not re-use any 
drained power steering fluid. 

Steering Wheel Free Play Inspection

430RX003

1. With the tires in the straight-ahead position, check 

the amount of steering wheel play by turning the 
wheel in both directions until the tires begin to 
move.

NOTE:  The wheel free play should be checked with the 
engine running.

Free play: 0 – 30 mm (0 – 1.18in)

2. Also check the steering wheel for play and 

looseness in the mount by moving it back and forth 
and sideways. When test driving, check for hard 
steering, steering shimmy and tendency to pull to 
one side. 

Front End Alignment Inspection and 
Adjustment

General Description

“Front End Alignment" refers to the angular relationship 
between the front wheels, the front suspension 
attaching parts and the ground.
Proper front end alignment must be maintained in order 
to insure efficient steering, good directional stability and 
to prevent abnormal tire wear.
The most important factors of front end alignment are 
wheel toe-in, wheel camber and axle caster.

Camber:

This illustration shows view from the front of the vehicle.

480RS004

Camber is the vertical tilting inward or outward of the 
front wheels. When the wheels tilt outward at the top, 
the camber is positive (+). When the wheels tilt inward 
at the top, the camber is negative (-). The amount of tilt 
measured in degrees from the vertical is called the 
camber angle (1). If camber is extreme or unequal 
between the wheels, improper steering and excessive 
tire wear will result. Negative camber causes wear on 
the inside of the tire, while positive camber causes wear 
to the outside.

Caster:

This illustration shows view from the side of the vehicle.

480RS005