Hummer H2. Manual - part 1702

The accessory drive components may have an affect on engine vibration. An overcharged air conditioning
(A/C) system, a power steering system restriction, or the incorrect fluid, or an extra load placed on the generator
are suggested items to inspect. To help identify an intermittent or an improper condition, vary the loads on the
accessory drive components.

Test Description

The number(s) below refer to the step(s) in the diagnostic table.

2: This test is to verify that the vibration is present during diagnosing. Other vehicle components may
cause a similar symptom such as the exhaust system, or the drivetrain.

3: This test is to verify that the drive belt(s) or accessory drive components may be causing the vibration.
Remove the drive belt(s) and operate the engine for a few seconds, this will verify if the vibration is
related to the drive belt(s) or not. With the drive belt(s) removed the water pump will not operate and the
engine may overheat. Also diagnostic trouble codes (DTCs) may set when the engine is operated with the
drive belt(s) removed.

4: The drive belt(s) may cause a vibration. While the drive belt(s) is removed this is the best time to
inspect the condition of the drive belt(s).

6: Inspection of the fasteners can eliminate the possibility that a incorrect bolt, nut, spacer, or washer was
installed.

8: This step should only be performed if the fan is driven by the drive belt. Inspect the engine cooling fan
for bent, twisted, loose, or cracked blades. Inspect the fan clutch for smooth operation. Inspect for a bent
fan shaft or bent mounting flange.

9: Inspect the water pump drive shaft for being bent. Also inspect the water pump bearings for smooth
operation and excessive play. Compare the water pump with a known, good water pump.

10: Accessory drive component brackets that are bent, cracked, or loose may put an extra strain on that
accessory drive component causing it to vibrate.

Drive Belt Vibration Diagnosis

Step

Action

Yes

DEFINITION: The following items are indications of drive belt vibration:

The vibration is engine-speed related.

The vibration may be sensitive to accessory load.

NOTE:

Refer to Belt Dressing Notice in Cautions and Notices.

Did you review the Symptoms - Engine
Mechanical diagnostic information, and
perform the necessary inspections?

Go to Step 2

Go to Symptoms

- Engine

Mechanical

Verify that the vibration is engine related.
Does the engine make the vibration?

Go to Step 3

Go to Diagnostic

Aids

1. Remove the drive belt(s). Refer to

Drive Belt Replacement - Accessory

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

DRIVE BELT FALLS OFF DIAGNOSIS

Diagnostic Aids

If the drive belt(s) repeatedly falls off the accessory drive pulley(s), this may be caused by a pulley
misalignment.

An extra load that is quickly applied or released by an accessory drive component may also cause the drive belt
(s) to fall off. Verify that the accessory drive component(s) are operating properly.

or Drive Belt Replacement - Air
Conditioning .

2. Operate the engine for no longer than

30 to 40 seconds.

Does the engine still make the vibration?

Go to Diagnostic Starting Point

- Vibration Diagnosis and

Correction in Vibration

Diagnosis and Correction

Go to Step 4

Inspect the drive belt(s) for wear, damage,
debris build-up and missing drive belt ribs.
Were any of these conditions found?

Go to Step 5

Go to Step 6

Install a new drive belt(s). Refer to Drive
Belt Replacement - Accessory or Drive
Belt Replacement - Air Conditioning .
Did you complete the replacement?

Go to Step 11

Inspect for incorrect, loose, and/or missing
fasteners.
Were any of these conditions found?

Go to Step 7

Go to Step 8

Replace any incorrect and/or missing
fastener.
Tighten any loose fasteners. Refer to
Fastener Tightening Specifications .
Were the fasteners replaced and/or
tightened?

Go to Step 11

Inspect for damaged fan blades or a bent fan
clutch shaft.
Did you find and correct the condition?

Go to Step 11

Go to Step 9

Inspect for a bent water pump drive shaft.
Did you find and correct the condition?

Go to Step 11

Go to Step 10

Inspect for a bent or cracked accessory drive
bracket(s).
Did you find and correct the condition?

Go to Step 11

1. Clear any codes.

2. Run the engine in order to verify the

repair.

Does the vibration still exist?

System OK

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

If the drive belt(s) is the incorrect length, the drive belt tensioner may not maintain the proper tension on the
drive belt(s).

Test Description

The number(s) below refer to the step(s) in the diagnostic table.

2: This inspection is to verify the condition of the drive belt(s). Damage may have occurred to the drive
belt(s) when the drive belt(s) fell off the pulley. Inspect the drive belt(s) for cuts, tears, sections of ribs
missing, or damaged belt plys.

4: Misalignment of the accessory drive pulley(s) may be caused from improper mounting or incorrect
installation of a accessory drive component, or the pulley may be bent inward or outward from a previous
repair. Test for a misaligned pulley using a straight edge in the pulley grooves across two or three pulleys.
If a misaligned pulley is found, refer to that accessory drive component for the proper removal and
installation procedure of that pulley.

5: Inspection of the accessory drive pulley(s) should include inspecting for bends, dents, or other damage
that would prevent the drive belt from seating properly in the pulley grooves or on the smooth surface of
a pulley when the back side of the drive belt(s) is used to drive the pulley.

6: Accessory drive component brackets that are bent or cracked will also cause the drive belt(s) to fall off.

7: Inspection of the fasteners can eliminate the possibility that a incorrect bolt, nut, spacer, or washer was
installed. Missing, loose, or incorrect fasteners may cause pulley misalignment from the accessory drive
bracket(s) moving under load. Over tightening the fasteners may cause misalignment of the accessory
component bracket(s).

Drive Belt Falls Off Diagnosis

Step

Action

Yes

DEFINITION: The drive belt(s) falls off the pulleys or may not ride correctly on the pulleys.

NOTE:

Refer to Belt Dressing Notice in Cautions and Notices.

Did you review the Symptoms - Engine Mechanical diagnostic
information, and perform the necessary inspections?

Go to

Step 2

Go to Symptoms -

Engine Mechanical

Inspect for a damaged drive belt(s).
Was a damaged drive belt(s) found?

Go to

Step 3

Go to Step 4

Install a new drive belt(s). Refer to Drive Belt Replacement -
Accessory or Drive Belt Replacement - Air Conditioning .
Does the drive belt(s) continue to fall off?

Go to

Step 4

System OK

Inspect for a misaligned accessory drive pulley(s).
Did you find and correct the condition?

Go to

Step 12

Go to Step 5

Inspect for a bent or dented accessory drive pulley(s).
Did you find and correct the condition?

Go to

Step 12

Go to Step 6

Inspect for a bent or a cracked accessory drive bracket(s).
Did you find and correct the condition?

Go to

Step 12

Go to Step 7

Inspect for incorrect, loose and/or missing fasteners.

Go to

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

DRIVE BELT EXCESSIVE WEAR DIAGNOSIS

Diagnostic Aids

Excessive wear on a drive belt(s) is usually caused by incorrect installation or the incorrect drive belt(s) for the
application.

Minor misalignment of the accessory drive pulley(s) will not cause excessive wear, but will probably cause the
drive belt(s) to make a noise or fall off.

Excessive misalignment of the accessory drive pulley(s) will cause excessive wear and may also make the drive
belt(s) fall off.

Test Description

The number(s) below refer to the step(s) in the diagnostic table.

2: This inspection is to verify that the drive belt(s) is correctly installed on all of the accessory drive
pulleys. Wear on the drive belt(s) may be caused by mis-positioning the drive belt(s) by one or more
grooves on a pulley(s).

3: The installation of a drive belt(s) that is too wide or too narrow will cause wear on the drive belt(s).
The drive belt(s) ribs should match all of the grooves on the pulleys.

4: This inspection is to verify that the drive belt(s) is not contacting any part of the engine or body while
the engine is operating. There should be sufficient clearance when the accessory drive components load
varies. The drive belt(s) should not come in contact with an engine or a body component when snapping
the throttle.

Were there any incorrect, loose and/or missing fasteners?

Step 8

Go to Step 9

1. Replace any incorrect and/or missing fasteners.

2. Tighten any loose fasteners. Refer to Fastener Tightening

Specifications .

Does the drive belt continue to fall off?

Go to

Step 9

System OK

Test the drive belt tensioner for correct operation. Refer to Drive
Belt Tensioner Diagnosis .
Does the drive belt tensioner operate correctly?

Go to

Step 11

Go to Step 10

Replace the drive belt tensioner. Refer to Drive Belt Tensioner
Replacement - Accessory or Drive Belt Tensioner Replacement -
Air Conditioning .
Does the drive belt continue to fall off?

Go to

Step 11

System OK

Inspect for a failed drive belt idler and/or tensioner pulley bearing.
Did you find and repair the condition?

Go to

Step 12

Run the engine in order to verify the repair.
Does the drive belt still fall off?

System OK

2004 Hummer H2

2004 ENGINE Engine Mechanical - 4.8L, 5.3L, and 6.0L - Hummer H2

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