Chevrolet Silverado / GMC Sierra. Service manual — part 238

DEFINITION: The following items are indications of chirping:

A high pitched noise that is heard once per revolution of the drive belt or a pulley.

Chirping may occur on cold damp start-ups and will subside once the vehicle reaches

normal operating temp.

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

A loud screeching noise that is caused by a slipping drive belt. This is unusual for a

drive belt with multiple ribs.

The noise occurs when a heavy load is applied to the drive belt, such as an air

conditioning compressor engagement snapping the throttle, or slipping on a seized

pulley or a faulty accessory drive component.

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

A high pitched continuous noise.

The noise may be caused by an accessory drive component failed bearing.

1

Did you review the drive belt symptom

operation and perform the necessary

inspections?

Go to Step 2

Go to Symptoms
- Engine
Mechanical

2

Verify that there is a chirping, squeal or whine

noise.

Does the engine make the chirping squeal or

whine noise?

Go to Step 3

Go to Diagnostic
Aids

3

1. Remove the drive belt.

If the engine has multiple drive belts,

remove the belts one at a time and

perform the test below each time a belt is

removed.

2. Operate the engine for no longer than 30-

40 seconds.

3. Repeat this test if necessary by removing

the remaining belts.

Does the chirping, squeal or whine noise still

exist?

Go to Symptoms
- Engine
Mechanical

Go to Step 4

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

4

If diagnosing a chirping noise, inspect for

severe pilling exceeding 1/3 of the belt groove

depth.

If diagnosing a squeal or whine noise, proceed

to step 13.

Do the belt grooves have pilling?

Go to Step 5

Go to Step 6

5

Clean the drive belt pulleys with a suitable

wire brush.

Did you complete the repair?

Go to Step 20

Go to Step 6

6

Inspect for misalignment of the pulleys.

Are any of the pulleys misaligned?

Go to Step 7

Go to Step 8

7

Replace or repair any misaligned pulleys.

Did you complete the repair?

Go to Step 20

Go to Step 8

8

Inspect for bent or cracked brackets.

Did you find any bent or cracked brackets?

Go to Step 9

Go to Step 10

9

Replace any bent or cracked brackets.

Did you complete the repair?

Go to Step 20

Go to Step 10

10

Inspect for improper, loose or missing

fasteners.

Did you find the condition?

Go to Step 11

Go to Step 12

11

1. Tighten any loose fasteners. Refer to

Fastener Tightening Specifications.

2. Replace any improper or missing

fasteners.

Did you complete the repair?

NOTE:

Refer to Fastener Notice .

Go to Step 20

Go to Step 12

12

Inspect for a bent pulley.

Did you find the condition?

Go to Step 18

Go to Step 19

13

Inspect for an accessory drive component
seized bearing or a faulty accessory drive

component.

If diagnosing a whine noise and the condition

still exist, proceed to Diagnostic Aids.

Did you find and correct the condition?

Go to Step 20

Go to Step 14

Test the drive belt tensioner for proper

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

DRIVE BELT RUMBLING AND VIBRATION DIAGNOSIS

Diagnostic Aids

The accessory drive components can have an affect on engine vibration. Vibration from the
engine operating may cause a body component or another part of the vehicle to make rumbling
noise. Vibration can be caused by, but not limited to the air conditioning (A/C) system over
charged, the power steering system restricted or the incorrect fluid, or an extra load on the
generator. To help identify an intermittent or an improper condition, vary the loads on the
accessory drive components.

The drive belt may have a rumbling condition that can not be seen or felt. Sometimes replacing
the drive belt may be the only repair for the symptom.

If replacing the drive belt, completing the diagnostic table, and the noise is only heard when the
drive belts are installed, there might be an accessory drive component with a failure. Varying the
load on the different accessory drive components may aid in identifying which component is
causing the rumbling noise.

Test Description

14

operation. Refer to Drive Belt Tensioner

Diagnosis.

Did you find and correct the condition?

Go to Step 20

Go to Step 15

15

Inspect for the correct drive belt length.

Did you find and correct the condition?

Go to Step 20

Go to Step 16

16

Inspect for misalignment of a pulley.

Did you find and correct the condition?

Go to Step 20

Go to Step 17

17

Inspect for the correct pulley size.

Did you find and correct the condition?

Go to Step 20

Go to Diagnostic
Aids

18

Replace the bent pulley.

Did you complete the repair?

Go to Step 20

Go to Step 19

19

Replace the drive belt. Refer to Drive Belt

Replacement - Accessory or Air

Conditioning Compressor Belt

Replacement.

Did you complete the repair?

Go to Step 20

Go to Diagnostic
Aids

20

Operate the system in order to verify the

repair.

Did you correct the condition?

System OK

Go to Step 3

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2

The numbers below refer to the step numbers on the diagnostic table.

2: This test is to verify that the symptom is present during diagnosing. Other vehicle
components may cause a similar symptom.

3: This test is to verify that one of the drive belts is causing the rumbling noise or vibration.
Rumbling noise may be confused with an internal engine noise due to the similarity in the
description. Remove only one drive belt at a time if the vehicle has multiple drive belts.
When removing the drive belts the water pump may not be operating and the engine may
overheat. Also DTCs may set when the engine is operating with the drive belts removed.

4: Inspecting the drive belts is to ensure that they are not causing the noise. Small cracks
across the ribs of the drive belt will not cause the noise. Belt separation is identified by the
plys of the belt separating and may be seen at the edge of the belt our felt as a lump in the
belt.

5: Small amounts of pilling is normal condition and acceptable. When the pilling is severe
the drive belt does not have a smooth surface for proper operation.

9: Inspecting of the fasteners can eliminate the possibility that the wrong bolt, nut, spacer,
or washer was installed.

11: This step should only be performed if the water pump is driven by the drive belt. Inspect
the water pump 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.

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

Step

Action

Yes

No

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

A low pitch tapping, knocking, or thumping noise heard at or just above idle.

Heard once per revolution of the drive belt or a pulley.

Rumbling may be caused from:

Pilling, the accumulation of rubber dust that forms small balls (pills) or strings in

the drive belt pulley groove

The separation of the drive belt

A damaged drive belt

NOTE:

Refer to Belt Dressing Notice .

2008 Hummer H2

2008 ENGINE Engine Mechanical - 6.2L - H2