Chevrolet Silverado / GMC Sierra. Manual - part 13
3. Place your thumb over the end of the hose in order to check for a vacuum. If there is no
vacuum at the hose, inspect for the following items:
Plugged hoses
The manifold port
4. Turn OFF the engine.
5. Inspect the PCV orifice in the valve cover for debris or blockage.
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.
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 two or three pulleys. If a misaligned pulley is
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
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 two or three 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
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:
NOTE:
Refer to Belt Dressing Notice .
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
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 belt(s).
Does the chirping, squeal or whine noise still
exist?
Go to Symptoms
- Engine
Mechanical
Go to Step 4
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
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado
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 13
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
14
Test the drive belt tensioner for proper
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
2008 Chevrolet Silverado 1500
2008 ENGINE Engine Mechanical - 4.3L - Sierra & Silverado