Chevrolet Silverado / GMC Sierra. Manual - part 237
Can you identify the type of fluid and the
approximate location of the leak?
Go to Step 10
Go to Step 6
6
1. Completely clean the entire engine and
surrounding components.
2. Apply an aerosol-type powder, baby
powder, foot powder, etc., to the suspected
area.
3. Operate the vehicle for several kilometers,
miles, at normal operating temperature and
at varying speeds.
4. Identify the type of fluid, and the
approximate location of the leak, from the
discolorations in the powder surface.
Can you identify the type of fluid and the
approximate location of the leak?
Go to Step 10
Go to Step 7
7
1. Visually inspect the suspected area. Use a
small mirror to assist in looking at hard to
see areas.
2. Inspect for leaks at the following locations:
Sealing surfaces
Fittings
Cracked or damaged components
Can you identify the type of fluid and the
approximate location of the leak?
Go to Step 10
Go to Step 8
8
Use the J 28428-E high-intensity black light kit
in order to identify the type of fluid, and the
approximate location of the leak. See Special
Tools. Refer to the manufacturer's instructions
when using the tool.
Can you identify the type of fluid and the
approximate location of the leak?
Go to Step 10
Go to Step 9
1. Visually inspect the suspected area. Use a
small mirror to assist in looking at hard to
see areas.
2. Inspect for leaks at the following locations:
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
CRANKCASE VENTILATION SYSTEM INSPECTION/DIAGNOSIS
9
Sealing surfaces
Fittings
Cracked or damaged components
Can you identify the type of fluid and the
approximate location of the leak?
Go to Step 10
System OK
10
1. Inspect the engine for mechanical damage.
Special attention should be shown to the
following areas:
Higher than recommended fluid levels
Higher than recommended fluid
pressures
Plugged or malfunctioning fluid filters
or pressure bypass valves
Plugged or malfunctioning engine
ventilation system
Improperly tightened or damaged
fasteners
Cracked or porous components
Improper sealants or gaskets, where
required
Improper sealant or gasket installation
Damaged or worn gaskets or seals
Damaged or worn sealing surfaces
2. Inspect the engine for customer
modifications.
Is there mechanical damage, or customer
modifications to the engine?
Go to Step 11
System OK
11
Repair or replace all damaged or modified
components.
Does the engine still leak oil?
Go to Step 1
System OK
Symptom
Correction
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
DRIVE BELT CHIRPING, SQUEAL, AND WHINE DIAGNOSIS
Diagnostic Aids
A chirping or squeal noise may be intermittent due to moisture on the drive belts or the
pulleys. It may be necessary to spray a small amount of water on the drive belts in order to
duplicate the customers concern. If spraying water on the drive belt duplicates the symptom,
cleaning the belt pulleys may be the probable solution.
If the noise is intermittent, verify the accessory drive components by varying their loads
making sure they are operated to their maximum capacity. An overcharged A/C system,
power steering system with a pinched hose or wrong fluid, or a generator failing are
suggested items to inspect.
A chirping, squeal or whine noise may be caused by a loose or improper installation of a
body or suspension component. Other items of the vehicle may also cause the noise.
The drive belts will not cause a whine noise.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
2: The 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 further with this table.
External oil leak
Inspect for any of the following conditions:
Restricted or kinked PCV hose or engine vent hose
Damaged, incorrect, or incorrectly installed PCV hose
Excessive crankcase pressure
Rough Idle
Inspect for any of the following conditions:
Restricted or kinked PCV hose or engine vent hose
Leaking (damaged) PCV hose
Vacuum hoses worn or not properly installed
Stalling or slow idle speed
Inspect for any of the following conditions:
Restricted or kinked engine vent hose
Leaking (damaged) PCV hose
High idle speed
Inspect for a leaking (damaged) PCV hose
Sludge in the engine
Inspect for restricted or kinked PCV hose or engine vent hose
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2
3: The noise may be an internal engine noise. Removing the drive belts one at a time and
operating the engine for a brief period will verify the noise is related to the drive belt. When
removing the drive belt 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: Inspect all drive belt pulleys for pilling. Pilling is the small balls or pills or it can be
strings in the drive belt grooves from the accumulation of rubber dust.
6: Misalignment of the pulleys may be caused from improper mounting of the accessory
drive component, incorrect installation of the accessory drive component pulley, or the
pulley bent inward or outward from a previous repair. Test for a misaligned pulley using a
straight edge in the pulley grooves across 2 or 3 pulleys. If a misaligned pulley is found refer
to that accessory drive component for the proper installation procedure for that pulley.
10: Inspecting of the fasteners can eliminate the possibility that a wrong bolt, nut, spacer, or
washer was installed.
12: Inspecting the pulleys for being bent should include inspecting for a dent or other
damage to the pulleys that would prevent the drive belt from not seating properly in all of
the pulley grooves or on the smooth surface of a pulley when the back side of the belt is
used to drive the pulley.
14: This test is to verify that the drive belt tensioner operates properly. If the drive belt
tensioner is not operating properly, proper belt tension may not be achieved to keep the
drive belt from slipping which could cause a squeal noise.
15: This test is to verify that the drive belt is not too long, which would prevent the drive
belt tensioner from working properly. Also if an incorrect length drive belt was installed, it
may not be routed properly and may be turning an accessory drive component in the wrong
direction.
16: Misalignment of the pulleys may be caused from improper mounting of the accessory
drive component, incorrect installation of the accessory drive component pulley, or the
pulley bent inward or outward from a previous repair. Test for a misaligned pulley using a
straight edge in the pulley grooves across 2 or 3 pulleys. If a misaligned pulley is found refer
to that accessory drive component for the proper installation procedure for that pulley.
17: This test is to verify that the pulleys are the correct diameter or width. Using a known
good vehicle compare the pulley sizes.
19: Replacing the drive belt when it is not damaged or there is not excessive pilling will
only be a temporary repair.
Step
Action
Yes
No
NOTE:
Refer to Belt Dressing Notice .
2008 Hummer H2
2008 ENGINE Engine Mechanical - 6.2L - H2