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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.

  1. 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.

    2.

  2. 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.

    3.

  3. 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.

    4.

  4. 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.

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

    6.

  6. 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.

    7.

  7. 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.

    8.

  8. 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.

    9.

  9. 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.

    10.

  10. This test is to verify that the pulleys are the correct diameter or width. Using a known good vehicle compare the pulley sizes.

    11.

  11. 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

Caution: 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 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.

    2. 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

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

    Caution: Refer to Fastener Caution in the Preface section.

  1. Tighten any loose fasteners. Refer to Fastener Tightening Specifications .
  2. Replace any improper or missing fasteners.

Did you complete the repair?

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

14

Test the drive belt tensioner for proper operation.

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 Symptoms - Engine Mechanical .

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

   


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