Hummer H1 (2006+). Manual - part 254

8-32

Steering System

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8.

Sticky flow control valve.

8.

Replace pump.

9.

Steering gear adjusted too tight.

9.

Replace the steering gear.

10. Improper front wheel alignment.

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. 

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.

Hose or air leakage in reservoir line. 

2.

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

 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 pass-
ing valve orifice edges. There is no rela-
tionship between this noise and steering 
performance. “Hiss” may be expected 
when the steering wheel is at end of 
travel or when slowly turning at stand-
still. 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. 

1.

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

2.

Steering linkage wear, play, looseness.

2.

Check linkage pivot points for wear.
Replace if necessary.

3.

Pressure hose touching other parts of 
vehicle.

3.

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

4.

Loose steering arm.

4.

Tighten the steering arm bolt.

 Power Steering Diagnosis Chart - part 1

Problem

Possible Cause

Correction

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 Steering System  8-33

5745804

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. 

5.

Replace the steering gear.

Excessive Wheel Kickback 
or Loose Steering

1.

Air in system.

1.

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

2.

Steering 

gear 

mounting 

loose. 

2.

Tighten attaching bolts to specified
torque.

3.

Steering linkage joints worn.

3.

Replace loose parts.

4.

Front wheel bearings incorrectly 
adjusted or worn.

4.

Adjust the bearings or replace with new
parts as necessary. 

5.

Steering gear improperly adjusted. 5.

Adjust 

to 

specifications.

6.

Damaged or worn steering gear.

6.

Replace the steering gear.

Vehicle Leads to One Side 
or the Other

1.

Keep in mind the road and wind condi-
tions. 

1.

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

1.

Front wheels misaligned.

1.

Adjust to specifications.

2.

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

2.

Replace the steering gear.

3.

Steering shaft binding.

3.

Align the column. 

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

1.

Low oil level in the pump.

1.

Add power steering fluid as required.

2.

Pump belt slipping.

2.

Adjust belt pressure.

3.

High internal leakage (steering gear or 
pump).

3.

Refer to “Power Steering System
Pressure Test” in this section. Repair as
needed.

 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.

1.

Remove the kinks or replace the hose.

2.

Foreign object stuck in the hose.

2.

Remove the foreign object or replace the
hose. 

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

1.

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

1.

Replace the steering gear.

2.

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

2.

Replace the steering gear.

 Power Steering Diagnosis Chart - part 2

Problem

Possible Cause

Correction

2-25-08

8-34

Steering System

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3.

Leakage at the valve body or a loose fit-
ting spool.

3.

Replace the steering gear.

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

1.

 Flow control valve stuck or inoperative.

1.

 Replace pump.

2.

Pressure plate not flat against the cam 
ring.

2.

Replace pump.

3.

Extreme wear of cam ring.

3.

Replace pump and flush system.

4.

Scored pressure plate, thrust plate, or 
rotor.

4.

Replace pump. Flush the system.

5.

Vanes sticking in rotor slots.

5.

Replace pump.

6.

Vanes not installed properly.

6.

Replace pump.

7.

Air in oil. 

7.

Locate source of leak and correct. Bleed
the system.

8.

Low oil level.

8.

Add power steering fluid as required.

9.

Pump belt slipping.

9.

Adjust belt. 

10. Damaged hoses or steering gear.

10. Replace as necessary.

Chirp Noise in Steering 
Pump or Belt Squeal (Partic-
ularly 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 
steering gear caused by restriction.

1.

Locate restriction and correct. 

Growl Noise in Steering 
Pump (Particularly Notice-
able 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. 

1.

Add power steering fluid as required. 

2.

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

2.

Torque the connector. Bleed the system.

Rattle or Knock Noise in 
Steering Pump

1.

Loose pump pulley.

1.

Replace pulley or pump.

2.

Pump vanes sticking in rotor slots.

2.

Replace pump.

3.

Pressure hose touching other parts of 
vehicle.

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. 

 Power Steering Diagnosis Chart - part 3

Problem

Possible Cause

Correction

11-1-05

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 Steering System  8-35

5745804

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 re-
moved for service. Procedure is as follows:

1.

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

2.

Switch the 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 the 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 the fluid level at “FULL COLD”. 

8.

While turning the wheel, check the fluid constantly. 

• There should be no bubbles. 

• If there are any bubbles, recheck the connections and repeat step 7. 

9.

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

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

11. Keep the engine running for two minutes. 

12. Continue turning the wheels back and forth until the 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 analyzer set J–44721 and hose fitting adapters J-44721-15. The analyzer
checks flow in gallons per minute (gpm) and min/max pressure in psi. Analyzer hose connection is shown in (Figure  8-31). Proce-
dure is as follows.

Pressure Test Procedure

NOTE: The fluid must be at operating temperature.

1.

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

2.

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

3.

Connect J–44721 analyzer hoses to the pump and the gear (Figure  8-31). Use fitting adapters J-44721-15 to connect the hoses
to the gear and the pump as needed.

4.

Add power steering fluid to the reservoir as required.

5.

Shift the transmission into Park.

6.

Open the analyzer valve.

7.

Start and run the engine at curb idle speed.

8.

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

a.

If the flow is less than 1.7 gpm (6.4 liters/min.), the pump is faulty.

11-1-05