Diagnostic information
If the noise is intermittent, check the accessory drive components by varying their loads and confirm that they are operating at peak performance. Excessive refrigerant in the air conditioning system, a restriction in the power steering circuit, or a faulty alternator are likely the cause of accessory drive belt squeal.
The noise may be caused by a loose or improperly installed body component, suspension component, or other item.
Description of the test
The item numbers below are the step numbers in the diagnostic chart.
- The noise may not be engine related. At this point, you want to confirm that the noise is coming from the engine. If the noise is not coming from the engine, you should not continue with this diagnostic procedure.
- This noise can be caused by internal engine components. Removing the drive belt and letting the engine run for a while can confirm or deny that the noise is related to the drive belt.
- Confirms that there is no bearing seizure in the accessory drive component. With the belt removed, check the accessory drive component bearings for ease and smoothness of rotation.
- Confirms that the drive belt tensioner is working properly. If the drive belt tensioner is not working properly, the drive belt tension will not be maintained, causing a squealing belt noise.
- Confirms that the belt is not too long and that it should not prevent the tensioner from working properly. Also, if an excessively long belt is installed, it may also be routed incorrectly and may rotate the accessory drive component in the wrong direction.
- Misalignment of pulleys can be caused by one of the following reasons:
- Incorrect fastening of the drive component of the units;
- Incorrect installation of the drive pulley of the units or
- Deformation or damage to the pulley.
- This test allows you to confirm that the pulley diameter and/or width are correct. Compare with pulley sizes on a known good vehicle.
Check pulley alignment by placing a straight edge across pulley grooves 2 or 3. If pulley misalignment is detected, refer to the appropriate component service information for installation and removal procedures.
Diagnostic table
Definition: Accessory drive belt squeal can be defined as a loud squealing noise caused by a slipping drive belt. Squealing rarely occurs on multi-ribbed belts. Drive belt squeal usually occurs when there is a heavy load on the belt, such as when the A/C compressor clutch engages, the throttle snaps, a seized pulley, or a defective accessory drive component.
| Step | Operation | Values | Yes | No |
| 1 |
Have you reviewed the information provided in the Symptoms section and performed the required checks?
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-
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Jump to operations 2
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Go to item Symptoms
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| 2 |
Confirm customer complaint. Is there a squealing noise?
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-
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Jump to operations 3
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See diagnostic recommendations in this section
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| 3 |
Is the screeching sound still present?
|
-
|
The drive system of the units is in order.
Go to "Symptoms" and start the noise diagnostic again
|
Jump to operations 4
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| 4 |
Inspect accessory drive components for bearing seizure and general faults.
Have bearing seizures and general faults in the accessory drive system been identified and corrected?
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-
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Jump to operations 9
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Jump to operations 5
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| 5 |
Check the correct operation of the accessory drive belt tensioner, see "Diagnosing the drive belt tensioner".
Tensioner problems found and corrected?
|
-
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Jump to operations 9
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Jump to operations 6
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| 6 |
Check that the accessory drive belt length is correct.
Have tensioner length issues been identified and resolved?
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-
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Jump to operations 9
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Jump to operations 7
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| 7 |
Check the alignment of the drive pulleys of the units along the plane.
Have the drive pulley misalignments of the units been detected and corrected?
|
-
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Jump to operations 9
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Jump to operations 8
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| 8 |
Check that the auxiliary drive pulleys are the correct size.
Incorrect pulleys found and replaced?
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-
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Jump to operations 9
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See diagnostic recommendations in this section
|
| 9 |
Reinstall the accessory drive belt and operate the system to confirm completion of the repair.
Is the screeching noise fixed?
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-
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The drive system of the units is in order
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Jump to "Symptoms" and restart the diagnostics
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