Diagnostic Information
If the noise is intermittent, test the accessory drive components by varying their loads to confirm that they are operating at peak performance. Too much refrigerant in the A/C system, an obstruction in the power steering circuit, or a bad alternator are all likely to be the cause of a squealing accessory drive belt.
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 table.
- The noise may not be engine related. At this stage, confirmation should be obtained that the noise is emitted by the engine. If it is not the engine that is making the noise, do not continue with this diagnostic procedure.
- This noise may be caused by internal engine components. If you remove the drive belt and let the engine run for a bit, you can confirm or deny that the noise is related to the drive belt.
- Confirms that there is no seized bearing in the accessory drive component. With the belt removed, check the bearings of the accessory drive components for ease and smoothness of rotation.
- Confirms proper operation of the drive belt tensioner. If the drive belt tensioner is not working properly, the drive belt tension will not be maintained, causing a squealing noise from the belt.
- Confirms that the belt is not too long and that this should not interfere with the correct operation of the tensioner. 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.
- Skewed pulleys can be caused by one of the following reasons:
- Incorrect mounting of the accessory drive component;
- Incorrect installation of the accessory drive pulley or
- Deformed or damaged pulley.
- This test allows you to confirm the correct diameter and / or width of the pulleys. Compare with pulley dimensions on a known good vehicle.
Check the alignment of the pulleys on the plane by applying a ruler to the grooves of 2 or 3 pulleys. If a misaligned pulley 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 sound caused by the drive belt slipping. Squealing rarely occurs on multi-ribbed belts. Drive belt squealing usually occurs when the belt is heavily loaded, such as when the A/C compressor clutch engages, the throttle sticks, a pulley seizes, or an accessory drive component fails.
Step | Operation | Values | Yes | No |
1 |
Have you reviewed the information in the section "Symptoms", and performed the required checks?
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-
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Go to operation 2
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Go to item Symptoms
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2 |
Acknowledge the customer's complaint. Is there a screeching noise?
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-
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Go to operation 3
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See diagnostic advice in this section
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3 |
Is the screeching sound still there?
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-
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The drive system of the aggregates is in order.
Go to "Symptoms" and restart noise diagnostics
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Go to operation 4
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4 |
Inspect the accessory drive components for bearing seizing and general faults.
Are bearing seizures and general faults in the accessory drive system found and corrected?
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-
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Go to operation 9
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Go to operation 5
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5 |
Check the correct operation of the accessory drive belt tensioner, refer to "Diagnosis of the drive belt tensioner".
Tensioner problems found and fixed?
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-
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Go to operation 9
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Go to operation 6
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6 |
Check the correct length of the accessory drive belt.
Have tensioner length issues been identified and resolved?
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-
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Go to operation 9
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Jump to Operation 7
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7 |
Check the alignment of the accessory drive pulleys on the plane.
Have misaligned accessory drive pulleys been detected and corrected?
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-
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Go to operation 9
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Jump to operation 8
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8 |
Check that the accessory drive pulleys are correctly sized.
Wrong pulleys found and replaced?
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-
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Go to operation 9
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See diagnostic advice in this section
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9 |
Reinstall the accessory drive belt and operate the system to confirm repair is complete.
Has the screeching noise been eliminated?
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-
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The drive system of the aggregates is in order
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Go to "Symptoms"and restart diagnostics
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