Hummer H2. Manual — part 1700

CRANKCASE VENTILATION SYSTEM INSPECTION/DIAGNOSIS

Crankcase Ventilation System Inspection/Diagnosis

DRIVE BELT CHIRPING DIAGNOSIS

Diagnostic Aids

The chirping noise may be intermittent due to moisture on the drive belt(s) or the accessory drive pulley(s). In
order to duplicate the customer's concern, it may be necessary to spray a small amount of water onto the drive
belt(s). If spraying water onto the drive belt(s) duplicates the symptom, cleaning the accessory drive pulley(s)
may be the most probable solution.

A loose or improper installation of a body or suspension component, or other item(s) on the vehicle may also
cause the chirping noise.

Test Description

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

Symptom

Correction

External oil leak

Inspect for any of the following conditions:

z

Restricted positive crankcase ventilation (PCV) valve

z

Restricted or kinked PCV hose or engine vent hose

z

Damaged, incorrect, or incorrectly installed PCV valve or hose

z

Excessive crankcase pressure

Rough Idle

Inspect for any of the following conditions:

z

Restricted PCV valve

z

Restricted or kinked PCV hose or engine vent hose

z

Leaking (damaged) PCV valve or hose

z

Vacuum hoses worn or not properly installed

Stalling or slow idle speed

Inspect for any of the following conditions:

z

Restricted PCV valve

z

Restricted or kinked PCV hose or engine vent hose

z

Leaking (damaged) PCV valve or hose

High idle speed

Inspect for a leaking (damaged) PCV valve or hose

Sludge in the engine

Inspect for any of the following conditions:

z

Restricted PCV valve

z

Restricted or kinked PCV hose or engine vent hose

2004 Hummer H2

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

2: The chirping noise may not be engine related. This step is to verify that the engine is making the noise.
If the engine is not making the noise do not proceed any further in this table.

3: The noise may be an internal engine noise. Remove the drive belt(s) and operate the engine for a few
seconds, this will verify if the chirping noise 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: Inspect the drive belt(s) for signs of pilling. Pilling is the small balls, pills, or strings in the drive belt
grooves caused by the accumulation of rubber dust.

6: Misalignment of the accessory drive pulley(s) may be caused from improper mounting or incorrect
installation of an accessory drive component, or the pulley may be bent inward or outward from a
previous repair. Test for a misaligned accessory drive 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 for that pulley.

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

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

14: Replacing the drive belt(s) when it is not damaged or there is not excessive pilling will only be a
temporary repair.

Drive Belt Chirping Diagnosis

Step

Action

Yes

No

DEFINITION: The following items are indications of chirping:

z

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

z

Chirping may occur on cold damp startup conditions and will subside once the vehicle reaches
normal operating temperature.

NOTE:

Refer to Belt Dressing Notice in Cautions and Notices.

1

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

Go to Step 2

Go to Symptoms -

Engine

Mechanical

2

Verify that there is a chirping noise.
Does the engine make the chirping noise?

Go to Step 3

Go to Diagnostic

Aids

3

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

Replacement - Accessory or Drive Belt
Replacement - Air Conditioning .

2. Operate the engine for no longer than 30 to

40 seconds.

Go to Engine Noise on

Start-Up, but Only

2004 Hummer H2

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

DRIVE BELT SQUEAL DIAGNOSIS

Does the chirping noise still exist?

Lasting a Few Seconds

Go to Step 4

4

Inspect for severe drive belt pilling exceeding 1/3 of
the drive belt groove depth.
Do the drive belt grooves have pilling?

Go to Step 5

Go to Step 6

5

Clean the accessory drive pulley(s) with a suitable
wire brush.
Were the accessory drive pulley(s) cleaned?

Go to Step 15

-

6

Inspect for a misaligned accessory drive pulley(s).
Is there a misaligned accessory drive pulley(s)?

Go to Step 7

Go to Step 8

7

Replace and/or repair the misaligned accessory
drive pulley(s).
Were the misaligned accessory drive pulley(s)
replaced and/or repaired?

Go to Step 15

-

8

Inspect for a bent or cracked accessory drive
bracket(s).
Did you find any bent or cracked accessory drive
bracket(s)?

Go to Step 9

Go to Step 10

9

Replace the bent and/or cracked accessory drive
bracket(s).
Was the bent and/or cracked accessory drive
bracket(s) replaced?

Go to Step 15

-

10

Inspect for incorrect, loose and/or missing fasteners.
Were there any incorrect, loose, and/or missing
fasteners found?

Go to Step 11

Go to Step 12

11

1. Replace any incorrect and/or missing

fasteners.

2. Tighten any loose fasteners. Refer to

Fastener Tightening Specifications .

Were the fasteners replaced and/or tightened?

Go to Step 15

-

12

Inspect for a bent accessory drive pulley(s).
Was a bent accessory drive pulley(s) found?

Go to Step 13

Go to Step 14

13

Replace the bent accessory drive pulley(s).
Was the bent accessory drive pulley(s) replaced?

Go to Step 15

-

14

Replace the drive belt(s). Refer to Drive Belt
Replacement - Accessory or Drive Belt
Replacement - Air Conditioning .
Was the drive belt(s) replaced?

Go to Step 15

-

15

1. Clear any codes.

2. Run the engine in order to verify the repair.

Does the chirping noise still exist?

-

System OK

2004 Hummer H2

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

Diagnostic Aids

A loose or improper installation of a body, or suspension component, or other item(s) on the vehicle may cause
the squeal noise.

If the squeal is intermittent, verify that it is not the accessory drive component(s) by varying their load(s),
making sure they are operating to their maximum capacity. An overcharged air conditioning (A/C) system, a
power steering system restriction or the incorrect fluid, or a failing generator are suggested items to inspect.

Test Description

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

2: The squeal may not be engine related. This step is to verify that the engine is making the noise. If the
engine is not making the noise do not proceed further in this table

3: The squeal may be an internal engine noise. Remove the drive belt(s) and operate the engine for a few
seconds, this will verify if the squealing noise is related to the drive belt(s) or an accessory drive
component. 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: This test is to verify that an accessory drive component(s) does not have a seized bearing. With the belt
(s) removed, test the bearings in the accessory drive component(s) for smooth operation. Also test the
accessory drive component(s) with the engine operating by varying the load on the accessory drive
component(s) to verify that the component(s) is operating properly.

5: This test is to verify that the drive belt(s) tensioner(s) are not operating properly. If the drive belt
tensioner(s) are not operating properly, proper belt tension may not be achieved to keep the drive belt(s)
from slipping which could cause a squealing noise.

6: This test is to verify that the drive belt(s) is not too long, which would prevent the drive belt tensioner
(s) from operating properly. Also if the incorrect length drive belt(s) was installed, it may not be routed
correctly and may be turning an accessory drive component in the incorrect direction.

7: 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 for that pulley.

8: Inspect the accessory drive pulley(s) to verify that they are the correct diameter or width. Using a
known good vehicle, compare the accessory drive pulleys.

Drive Belt Squeal Diagnosis

Step

Action

Yes

No

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

NOTE:

Refer to Belt Dressing Notice in Cautions and Notices.

2004 Hummer H2

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