Isuzu N-Series. Service manual - part 107

Noisy relief valve.
There is some noise in all power steering
systems. One of the most common is a
hissing sound most evident at standstill
parking. Hiss is a high frequency noise simi-
lar to that experienced while slowly closing
a water tap. The noise is present in every
valve and results from high velocity fluid
passing valve orifice edges. There is no
relationship between this noise and perfor-
mance of the steering. “Hiss” may be
expected when the steering wheel is at end
of travel of when slowly turning at stand still.

Do not replace the valve unless “hiss” is
extremely objectionable. A replacement
valve will also exhibit slight noise and is not
always a cure.

Rattle or Chuckle
Noise in the Steering
Gear

1. Gear housing loose on frame.

1. Check gear mounting. Torque the bolts

to specifications.

2. Steering linkage looseness.

2. Check linkage pivot points for wear. Re-

place if necessary.

3. Pressure house touching other parts of

the truck.

3. Adjust the hose position. Do not bend

tubing by hand.

4. Loose pitman shaft over center adjust-

ment. A slight rattle may occur on turns
because of increased clearance off the
“high point.” This is normal and clear-
ance must not be reduced below speci-
fied limits to eliminate this slight rattle.

4. Adjust.

5. Loose pitman arm.

5. Torque the pitman arm nut.

Groan Noise in the
Steering Pump

1. Low oil level.

1. Fill the reservoir to the proper level.

2. Air in the oil. Poor pressure house con-

nection.

2. Torque the connector. Bleed the system.

Rattle or Knock
Noise in the Steering
Pump

Loose pump gear nut.

Torque the nut.

Rattle Noise in the
Steering Pump

1. Vanes not installed properly.

1. Install properly.

2. Vanes sticking in the rotor slots.

2. Repair or replace.

Switch Noise in the
Steering Pump

Defective flow control valve.

Replace or repair.

Whine Noise in the
Steering Pump

Pump shaft bearing scored.

Replace the housing and shaft. Flush and
bleed the system.

Growl Noise in the
Steering Pump

Excessive back pressure in houses or the
steering gear caused by restriction.

Locate the restriction and correct. Replace
the part if necessary.

Growl Noise in the
Steering Pump (Par-
ticularly Noticeable
at Standstill Parking)

1. Scored pressure plates, thrust plate or

rotor.

1. Replace the parts and flush the system.

2. Extreme wear of the cam ring.

2. Replace the parts.

SERVICE INFORMATION 00-3

Excessive Play or
Looseness in the
Steering System
(Steering Wanders)

1. Front wheel bearing loosely adjustment.

1. Adjust the bearing or replace with new

parts as necessary.

2. Worn coupling or steering shaft joints.

2. Replace.

3. Worn steering linkage ball joints.

3. Replace steering linkage.

4. Worn upper or lower ball joints.

4. Replace ball joints.

5. Steering wheel loose on the shaft, loose

pitman arm, tie rods, steering arms, or
steering linkage ball studs.

5. Torque the fastener.

6. Steering gear worm bearing loosely ad-

justed.

6. Adjust the preload.

7. Excessive pitman shaft to ball nut lash in

the steering gear.

7. Adjust the preload.

8. Toe-in out of adjustment or worn drag

link or tie rod sockets.

8. Replace the tie rod ends if worn, adjust to

correct the toe-in, and inspect the steer-
ing arm and tie rod for bent condition.

9. Steering system out of alignment.

9. Align caster, camber, and toe-in.

Inspect spring components for condition
and wear. Repair or replace as required.

10. Tires badly worn, edge of the tires are

rounded off.

10. Install new tires, and check alignment;

abnormal tire wear indicates improper
alignment.

11. Lack of lubrication in the linkage and

kingpins.

11. Lubricate. Free up any components

which are frozen and will not take lubrica-
tion.

12. Air in the system.

12. Add oil to the pump reservoir and bleed

the system. Check hose connectors for
proper torque.

13. Steering gear mounting loose.

13. Tighten attaching bolts to the specified

torque.

PROBLEM

POSSIBLE CAUSE

CORRECTION

00-4 SERVICE INFORMATION

Vibration and
Shimmy

1. Seal damage and leakage resulting in

loss of lubricant, corrosion and exces-
sive wear.

1. Replace damaged parts as necessary.

2. Tires, wheels, or brake drums out of bal-

ance.

2. Balance the tires and wheels, preferably

with an on-vehicle type balancer, as this
method balances the entire wheel and
drum assembly.

3. Bent wheel or out of bound tire.

Wheel nuts torqued unevenly.

3. Replace the wheel and remount the tire,

or replace the assembly.

4. Loose steering linkage components.

4. Adjust, torque, and repair the linkage as

necessary.

5. Worn steering linkage ball joints.

5. Replace steering linkage.

6. Worn upper or lower end ball joints.

6. Replace ball joints.

7. Wheel loose on the hub.

7. Inspect the wheel bolt holes for damage,

and replace the wheel or torque the nuts.

8. Drive line universal joints rough or defec-

tive. This condition may be confused with
steering vibration.

8. Repair the drive line.

9. Engine misses or is out of balance, this

may also be confused with steering
shimmy.

9. Correct the miss in the engine, or repair

the out of balance condition, clutch, pres-
sure plate, or harmonic balancer, etc.

10. Faulty shock absorbers.

10. Replace the shock absorbers.

Hard Steering or
Excessive Effort
Required at Steer-
ing Wheel

1. Low or uneven tire pressure.

1. Inflate to specified pressures.

2. Steering linkage kingpins or ball joints

need lubrications.

2. Lubricate, and free up kingpins or ball

joints. Make certain all fittings take lubri-
cant properly.

3. Tight or frozen intermediate rod, tie rod

or idler socket.

3. Lubricate or replace as necessary.

4. Steering gear to column misalignment.

4. Align the column.

5. Steering gear adjust too tightly.

5. Adjust preload.

6. Front wheel alignment incorrect.

6. Check alignment and correct as neces-

sary.

7. Steering gear adjusted too tight.

7. Adjust the steering gear.

8. Frozen or tight shaft bearings.

8. Replace the bearings.

9. Lower the U-joint flange rubbing against

the adjuster.

9. Loosen the bolt, assemble and torque

properly.

10. Tight or binding conditions in steering

column.

10. Adjust the steering column.

11. Power cylinder rod nicked or marred.

11. Replace the cylinder.

PROBLEM

POSSIBLE CAUSE

CORRECTION

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