Hummer H1 (2002+). Manual - part 128

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 Steering System  8-19

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05745159

POWER STEERING SYSTEM DIAGNOSIS CHARTS

The diagnosis charts are guidelines to potential system faults.
The charts list potential faults in order of probability (most
probable to least probable).

While the charts outline common faults, they may not cover all
possible problem causes. Inspection and diagnosis with ana-
lyzer set J–25323 should be used to confirm a pump or gear
problem. 

Table 1  Power Steering Diagnosis Chart - part 1

Problem

Possible Cause

Correction

Poor Return of Steering

1.

Tires under-inflated.

2.

Lower coupling flange rubbing against 
the steering gear adjuster plug.

3.

Steering wheel rubbing against direc-
tional signal housing. 

4.

Binding steering linkage, or ball joints. 

5.

Steering gear to column misalignment. 

6.

Tie rod not centralized. 

7.

Lack of lubricant in the suspension ball 
joints and steering linkage. 

8.

Stuck or plugged valve spool. 

9.

Improper front wheel alignment. 

10. Steering gear adjusted too tightly. 

11. Kink in return hose. 

1.

Inflate to specified pressure. 

2.

Loosen the pinch bolt and assemble 
properly. 

3.

Adjust the steering jacket. 

4.

Replace the affected parts. 

5.

Align the column. 

6.

Adjust tie rod ends as required. 

7.

Lubricate. 

8.

Remove, clean, or replace the valve. 

9.

Check and adjust to specifications. 

10. Adjust over-center and thrust bear-

ing preload to specifications. 

11. Replace the hose. 

Steering Wheel Surges or Jerks 
When Turning With Engine Run-
ning Especially During Parking

1.

Low oil level in pump. 

2.

Loose pump drive belt. 

3.

Sticky flow control valve. 

4.

Insufficient pump pressure. 

1.

Add power steering fluid as required. 

2.

Adjust bolt. 

3.

Replace or clean the control valve. 

4.

Test system with analyzer. 

Hard Steering Effort in Both 
Directions

1.

Low tire pressure. 

2.

Lack of lubricant in suspension or ball 
joints (Worn/contaminated joints). 

3.

Binding of steering linkage, or ball 
joints. 

4.

Steering gear to column misalignment. 

5.

Pump belt slipping. 

6.

Low fluid level in reservoir. 

7.

High internal leakage (steering gear or 
pump). 

8.

Sticky flow control valve. 

9.

Steering gear adjusted too tight. 

10. Improper front wheel alignment

1.

Adjust the tire pressure. 

2.

Lubricate and relubricate at proper 
intervals or replace joints. 

3.

Replace all affected parts. 

4.

Align the steering column. 

5.

Adjust belt. 

6.

Fill to proper level. Inspect lines and 
joints for external leakage. 

7.

Test system with analyzer. 

8.

Replace pump.

9.

Adjust over-center and thrust bear-
ing reload to specifications. 

10. Check and adjust to specifications. 

Foaming Milky 
Looking Power Steering Fluid, 
Low Level and Possible Low
Pressure

1.

Air in the fluid and loss of fluid due to 
internal pump leakage causing overflow. 

2.

Hose or air leakage in reservoir line. 

1.

Check for leak and correct. Bleed 
system. Extremely cold temperatures 
will cause system aeration should the 
oil level be low. If oil level is correct 
and pump still foams, remove pump 
from vehicle and separate reservoir 
from housing. 

2.

Check welsh plug and housing for 
cracks. If plug is loose or housing is 
cracked, replace housing.

8-20

Steering System

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Table 2   Power Steering Diagnosis Chart - part 2

Problem

Possible Cause

Correction

“Hiss” Noise

1.

Noisy relief valve in the pump. 

1.

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. 
The noise is present in every valve and 
results from high velocity fluid passing 
valve orifice edges. There is no relation-
ship between this noise and steering per-
formance. “Hiss” may be expected when 
the steering wheel is at end of travel or 
when slowly turning at standstill. Do not 
replace the pump unless “hiss” is 
extremely loud and continuous. A 
replacement pump will also exhibit slight 
noise and is not always a cure for hiss. 

Rattle or Chuckle Noise in 
Steering Gear

1.

Gear loose on the frame. 

2.

Steering linkage wear, play, looseness. 

3.

Pressure hose touching other parts of 
vehicle. 

4.

Loose steering arm. 

5.

Improper over-center adjustment. A 
slight rattle may occur on turns because 
of increased clearance off the “high 
pint”. This is normal and clearance must 
not be reduced below specified limits to 
eliminate this slight rattle. 

1.

Check the gear mounting bolts. Torque 
the bolts to specifications. 

2.

Check linkage pivot points for wear. 
Replace if necessary. 

3.

Adjust the hose position. Do not bend 
tubing by hand. 

4.

Tighten the steering arm bolt. 

5.

Adjust to specification.

Excessive Wheel Kickback 
or Loose Steering

1.

Air in system. 

2.

Steering gear mounting loose. 

3.

Steering linkage joints worn. 

4.

Front wheel bearings incorrectly 
adjusted or worn. 

5.

Steering gear improperly adjusted. 

6.

Damaged or worn steering gear. 

1.

Add oil to the pump reservoir and bleed. 
Check hose connectors for proper torque. 

2.

Tighten attaching bolts to specified 
torque. 

3.

Replace loose parts. 

4.

Adjust the bearings or replace with new 
parts as necessary. 

5.

Adjust to specifications. 

6.

Disassemble and repair the steering gear. 

Vehicle Leads to One Side 
or the Other

1.

Keep in mind the road and wind condi-
tions. 

2.

Front wheels misaligned. 

3.

Unbalanced steering gear valve. If this is 
the cause, steering effort will be very 
light in direction of lead and heavy in 
opposite direction. 

4.

Steering shaft binding. 

1.

Test the vehicle, going in both directions, 
on a flat road. 

2.

Adjust to specifications. 

3.

Replace the gear valve body. 

4.

Align the column. 

Momentary Increase in 
Effort when Turning the 
Wheel Quickly to the Right 
or Left

1.

Low oil level in the pump. 

2.

Pump belt slipping. 

3.

High internal leakage (steering gear or 
pump). 

1.

Add power steering fluid as required. 

2.

Adjust belt pressure. 

3.

Refer to “Power Steering System Pres-
sure Test” in this section. Repair as 
needed. 

 

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 Steering System  8-21

 

 

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05745159

 

Table 3   Power Steering Diagnosis Chart - part 3

 

Problem

Possible Cause

Correction

 

Low Oil Pressure Due to 
Restriction in the Hose

1.

Check for kinks in hose. 

2.

Foreign object stuck in the hose. 

1.

Remove the kinks or replace the hose. 

2.

Remove the foreign object or replace the 
hose. 

Low Oil Pressure Due to 
Steering Gear.
Refer to “Power Steering Sys-
tem Test” in this Section. 

1.

Pressure loss in cylinder due to worn rack 
piston ring or scored housing bore. 

2.

Leakage at the valve rings and valve body 
to the worm seal. 

3.

Leakage at the valve body or a loose fitting 
spool. 

1.

Disassemble the steering gear. Inspect the 
ring and housing bore. Replace the 
affected parts. 

2.

Disassemble steering gear and replace 
seals. 

3.

Replace the valve. 

Low Oil Pressure Due to 
Steering Pump.
Refer to “Power Steering Sys-
tem Test” in this Section. 

1.

Flow control valve stuck or inoperative. 

2.

Pressure plate not flat against the cam ring. 

3.

Extreme wear of cam ring. 

4.

Scored pressure plate, thrust plate, or 
rotor. 

5.

Vanes sticking in rotor slots. 

6.

Vanes not installed properly. 

7.

Air in oil. 

8.

Low oil level. 

9.

Pump belt slipping. 

10. Damaged hoses or steering gear. 

1.

Replace pump. 

2.

Replace pump. 

3.

Replace pump and flush system. 

4.

Replace pump. Flush the system. 

5.

Replace pump. 

6.

Replace pump. 

7.

Locate source of leak and correct. Bleed 
the system. 

8.

Add power steering fluid as required. 

9.

Adjust belt. 

10. Replace as necessary.

Chirp Noise in Steering Pump 
or Belt Squeal (Particularly 
Noticeable At Full Wheel 
Travel and Standstill Parking) 

1.

Pump belt slipping. 

1.

Replace belt. 

Growl Noise in Steering Pump 1.

Excessive back pressure in hoses or steer-
ing gear caused by restriction.

1.

Locate restriction and correct. 

Growl Noise in Steering Pump 
(Particularly Noticeable 
Standstill Parking) 

1.

Scored pressure plates, thrust plate, or 
rotor. Extreme wear of cam ring. 

1.

Replace pump and flush system. 

Groan Noise in 
Steering Pump

1.

Low oil level. 

2.

Air in the oil. Poor pressure hose connec-
tion. 

1.

Add power steering fluid as required. 

2.

Torque the connector. Bleed the system. 

Rattle or Knock Noise in 
Steering Pump

1.

Loose pump pulley. 

2.

Pump vanes sticking in rotor slots. 

3.

Pressure hose touching other parts of vehi-
cle. 

1.

Replace pulley or pump. 

2.

Replace pump. 

3.

Adjust hose position. 

Swish Noise in Steering Pump 1.

Faulty flow control valve. 

1.

Replace pump. 

Whine Noise in 
Steering Pump

1.

Pump shaft bearing scored. 

1.

Replace pump. 

 

8-22

Steering System

 

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PURGING AIR FROM THE POWER STEERING 
SYSTEM

 

Air must be bled from the system before pressure testing and
anytime the hoses are disconnected or the pump and/or gear is
removed for service. Procedure is as follows:

1.

All hose connections must be tight. Loose connections 
might not leak but could allow air into system. 

2.

Switch ignition off. 

3.

Turn the steering wheel full left. 

4.

Top off the reservoir fluid level to "FULL COLD" but do
not replace the reservoir filler cap. If fluid was added to
the reservoir, allow it to settle for 2-3 minutes before
proceeding.

5.

Raise and support the vehicle front end. The front tires
only have to clear the shop floor.

6.

Shift the transmission into Park.

7.

With an assistant checking the fluid level and condition,
turn steering wheel lock-to-lock at least 40 times. The
engine remains off. 

• Trapped air may cause fluid to overflow. Thoroughly 

clean any spilled fluid to allow for leak check. 

• Keep fluid level at "FULL COLD". 

8.

While turning wheel, check fluid constantly. 

• There should be no bubbles. 

• If there are any bubbles, recheck the connections and re-

peat step 7. 

9.

Start the engine. With engine idling, maintain fluid level.
Install reservoir cap. 

10. Return wheels to center. Lower front wheels to the

ground. 

11. Keep engine running for two minutes. 

12. Continue turning wheels back and forth until bubbles no

longer appear in fluid.

13. Verify the following conditions:

• smooth power assist

• noiseless operation

• proper fluid level

• no system leaks

• proper fluid condition

14. If all conditions apply, the procedure is complete. 

 

POWER STEERING SYSTEM PRESSURE TEST

 

Power steering system performance can be checked with ana-
lyzer set J– 25323 and hose fitting adapters J– 33141. The ana-
lyzer checks flow in gallons per minute (gpm) and min/max
pressure in psi. Analyzer hose connection is shown in
Figure 8-30. Procedure is as follows.

 

Pressure Test Procedure

 

NOTE: 

 

Fluid must be at operating temperature.

1.

Purge air from power steering system. Refer to procedure 
in this section.

2.

Position drain pan under pump and gear to catch spilled
fluid.

3.

Connect J–25323 analyzer hoses to pump and gear
(Figure 8-30). Use fitting adapters J–33141 to connect
hoses to gear and pump as needed.

4.

Add power steering fluid to reservoir as required.

5.

Shift transmission into Park.

6.

Open analyzer valve.

7.

Start and run engine at curb idle speed.

8.

Note and record flow rate and pressure indicated on
analyzer gauge. 

a.

If flow is less than 1.32 gpm (5 liters/min.), pump is
faulty.

b.

If pressure is above 150 psi, (1035 kPa), either a hose
is restricted or a problem exists within the gear.

c.

If flow is greater than 1.32 gpm and pressure is less
than 150 psi, continue test.

9.

Partially close the analyzer valve, allow pressure to build
to 620 psi (4278 kPa), and record flow rate.

a.

If flow rate decreases by more than 1 gpm (3.7 L/
minute) from the reading in step 8, the pump is at
fault.

b.

If flow rate remains about the same, continue test. 

10. Completely close and partially open the analyzer valve

three times in succession. Note and record maximum
pressures each time. 

 

CAUTION: 

 

Do not close the analyzer valve for more than 3-4

seconds at a time. Longer periods will result in rapid fluid
overheat and pump damage.

 

11. If pump maximum pressures recorded in step 10 were less

than 1150 psi (7929 kPa), the pump is at fault. However, if
pressures are at, or above specified limit, continue with
test.

12. Increase engine speed to 1500 rpm and record flow rate.

a.

If flow rate remains within 1 gpm of flow recorded in
step 8, continue test.

b.

If flow rate drops by more than 1 gpm (3.7L/ minute),
pump control valve is faulty.

 

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