GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2004 🢒 GMC C Sierra - 2WD 🢒 Engine 🢒 Engine Mechanical - 6.6L (LB7) 🢒 Drive Belt Chirping Diagnosis

Diagnostic Aids

The chirping noise may be intermittent due to moisture on the drive belt 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. If spraying water onto the drive belt duplicates the symptom, cleaning the accessory belt 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.

If a chirping noise occurs during engine shutdown, this is considered normal and is due to the engine's high compression.

Test Description

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

  1. 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 further with this table.

    2.

  2. The noise may be an internal engine noise. Remove the drive belt and operate the engine for a few seconds, this will verify if the chirping noise is related to the drive belt or not. With the drive belt removed the cooling fan will not operate and the engine may overheat. Also diagnostic trouble codes (DTCs) may set when the engine is operated with the drive belt removed.

    3.

  3. Inspect the drive belt for signs of pilling. Pilling is the small balls, pills or strings in the drive belt grooves caused by the accumulation of rubber dust.

    4.

  4. 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 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 removal and installation procedure for that pulley.

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

    6.

  6. 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 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.

    7.

  7. 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

Notice: Do not use belt dressing on the drive belt. Belt dressing causes the breakdown of the composition of the drive belt. Failure to follow this recommendation will damage the drive belt.

DEFINITION: The following items are indications of chirping:

    • A high pitched noise that is heard once per revolution of the drive belt or a accessory drive pulley.
    • Chirping may occur on cold damp startup conditions and will subside once the vehicle reaches normal operating temperature.

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. Refer to Drive Belt Replacement .
  2. Operate the engine for no longer than 30 to 40 seconds.

Does the chirping noise still exist?

Go to Engine Noise on Start-Up, but Only Lasting a Few Seconds

Go to Step 4

4

Inspect for severe drive belt pilling exceeding 1/3 of the belt groove depth.

Does the drive belt grooves have pilling?

Go to Step 5

Go to Step 6

5

Clean the accessory drive belt pulley(s) with a suitable wire brush.

Were the accessory drive belt pulley(s) cleaned?

Go to Step 15

--

6

Inspect for a misaligned accessory drive pulley(s).

Is there a misaligned 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).

Is there a bent and/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

Go to Step 12

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. Refer to Drive Belt Replacement .

Was the drive belt 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