Isuzu Trooper (2000 year). Manual — part 43

2A–2

POWER ASSISTED SYSTEM

Service Precaution

WARNING: THIS VEHICLE HAS A SUPPLEMENTAL
RESTRAINT SYSTEM (SRS). REFER TO THE SRS
COMPONENT AND WIRING LOCATION VIEW IN
ORDER TO DETERMINE WHETHER YOU ARE
PERFORMING SERVICE ON OR NEAR THE SRS
COMPONENTS OR THE SRS WIRING. WHEN YOU
ARE PERFORMING SERVICE ON OR NEAR THE SRS
COMPONENTS OR THE SRS WIRING, REFER TO
THE SRS SERVICE INFORMATION. FAILURE TO
FOLLOW WARNINGS COULD RESULT IN POSSIBLE
AIR BAG DEPLOYMENT, PERSONAL INJURY, OR
OTHERWISE UNNEEDED SRS SYSTEM REPAIRS.

CAUTION: Always use the correct fastener in the
proper location. When you replace a fastener, use
ONLY the exact part number for that application.
ISUZU will call out those fasteners that require a
replacement after removal. ISUZU will also call out
the fasteners that require thread lockers or thread
sealant. UNLESS OTHERWISE SPECIFIED, do not
use supplemental coatings (Paints, greases, or other
corrosion inhibitors) on threaded fasteners or
fastener joint interfaces. Generally, such coatings
adversely affect the fastener torque and the joint
clamping force, and may damage the fastener. When
you install fasteners, use the correct tightening
sequence and specifications. Following these
instructions can help you avoid damage to parts and
systems.

General Description

The hydraulic power steering system consists of a pump,
an oil reservoir, a steering gear, a pressure hose and a
return hose.

Power Steering Gear

A03RS001

The power steering gear has a recirculating ball system
which acts as a rolling thread between the worm shaft and
the rack piston. When the worm shaft is turned right, the
rack piston moves up in gear.
Turning the worm shaft left moves the rack piston down in
gear. The rack piston teeth mesh with the sector gear,
which is part of the sector shaft.
Turning the worm shaft turns the sector shaft, which turns
the wheels through the steering linkage.

The control valve in the steering gear directs the power
steering fluid to either side of the rack piston.
The rack piston converts the hydraulic pressure into a
mechanical force. If the steering system becomes
damaged and loses hydraulic pressure, the vehicle can
be controlled manually.

POWER ASSISTED SYSTEM

2A–3

Hydraulic Pump

442RV006

The hydraulic pump is a vane-type design. There are two
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.

Pressure Switch

When hydraulic pressure reaches 3650

±

350 kPa (530

±

50 psi), the pressure switch of the power steering pump
closes causing the Powertrain Control Module (PCM) to
actuate the idle air control valve, which increases the
engine rpm to prevent the overload-induced engine
speed slow down. The switch opens when hydraulic
pressure drops to 3150

±

350 kPa (460

±

50 psi).

2A–4

POWER ASSISTED SYSTEM

Steering Linkage

433RS007

Legend

(1) Center Track Rod Assembly
(2) Outer Track Rod Assembly
(3) Pitman Arm

(4) Relay Lever
(5) Rod End,Outer
(6) Track Rod
(7) Rod End,Inner

The steering linkage consists of a pitman arm, relay lever,
center track rod, and two adjustable outer track rods.
When the steering wheel is turned, the gear rotates the
pitman arm which forces the center track rod to one side.
The outer track rods, connected to the center track rod by
ball studs, transfers the steering force to the wheels. The
outer track rods are adjustable and are used for toe-in
adjustments. The center track rod is supported by the
pitman arm and relay lever. The relay lever pivots on a
support attached to the frame.
The overall condition of the steering linkage affects
steering performance. If parts are bent, damaged, worn
or poorly lubricated, improper and possibly dangerous
steering action will result.
Whenever any steering linkage components are repaired
or replaced, check the steering geometry and front end
alignment. Refer to Front End Alignment Inspection and
Adjustment in this section.

POWER ASSISTED SYSTEM

2A–5

Steering Column

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
ELECTRICAL EQUIPMENT OTHER THAN
SPECIFIED IN THIS MANUAL. DO NOT USE A
NON-POWERED PROBE-TYPE TESTER.

INSTRUCTION IN THIS MANUAL MUST BE FOL-
LOWED CAREFULLY, OTHERWISE PERSONAL IN-
JURY 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.
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 ensure 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.

Diagnosis

Since the problems in steering, suspension, wheels and
tires involve several systems, they must all be considered
when diagnosing a complaint. To identify the symptom,
always road test the vehicle first. Proceed with the follow-
ing preliminary inspections and correct any defects which
are found.

1. Inspect tires for proper pressure and uneven wear.
2. Raise vehicle on a hoist, then inspect front and rear

suspension and steering linkage for loose or
damaged parts.

3. Spin the front wheels. Inspect for out-of-round tires,

out-of-balance tires, loose and/or rough wheel
bearings.

General Diagnosis

Condition

Possible cause

Correction

Vehicle Pulls

Mismatched or uneven tires.

Replace tire.

Tires not adequately inflated.

Adjust tire pressure.

Broken or sagging springs.

Replace spring.

Radial tire lateral force.

Replace tire.

Improper wheel alignment.

Adjust wheel alignment.

Brake dragging in one wheel.

Repair brake.

Loose, bent or broken front or rear
suspension parts.

Tighten or replace the appropriate
suspension part(s).

Faulty shock absorbers.

Replace shock absorber.

Abnormal or Excessive Tire Wear

Sagging or broken spring.

Replace spring.

Tire out of balance.

Balance or replace tire.

Improper wheel alignment.

Check front end alignment.

Faulty shock absorber.

Replace shock absorber.

Hard driving.

Replace tire.

Overloaded vehicle.

Replace tire and reduce load.

Tires not rotated periodically.

Replace or rotate tire.

Worn or loose road wheel bearings.

Replace wheel bearing.

Wobbly wheel or tires.

Replace wheel or tire.

Tires not adequately inflated.

Adjust the pressure.

Wheel Hop

Blister or bump on tire.

Replace tire.

Improper shock absorber operation.

Replace shock absorber.