- A loud squealing noise that occurs when the drive belt slips (very rare on multi-groove drive belts)
- Drive belt squeal typically occurs when there is a heavy load on the belt, such as when the A/C compressor clutch engages, the throttle snaps, slips on a seized pulley, or when an accessory drive component fails.
Diagnostic information
The characteristic squealing noise can also be caused by a loose or improperly installed body or suspension part, or other elements on the vehicle.
If the squeal is intermittent, it is necessary to check whether it is caused by changes in the load on the auxiliary drive component, to do this, ensure that they operate at maximum power. It is recommended to pay attention to the following - excessive freon charge in the air conditioning system, jamming in the power steering system or filling the system with inappropriate fluid, generator failure.
Description of the test
The numbers below refer to the operations in the diagnostic table:
2. This squealing noise may not be related to the engine. At this point, you should verify that the engine is making the noise. If the engine is not the cause of the noise, do not use this chart for further diagnosis.
3. This squealing noise can be caused by internal engine components. Removing the drive belt and running the engine for a few seconds will help determine whether or not the squealing noise is related to the drive belt or any accessory drive component. Without the drive belt, the water pump will not operate and the engine may overheat. Diagnostic trouble codes (DTCs) may also be set if the engine is running without the drive belt.
4. This test checks to see if any of the accessory drive components are binding in their bearings. With the belt removed, check all accessory drive component bearings for smooth rotation. Also test the accessory drive components with the engine running, varying the load on the accessory drive components to check for proper operation.
5. This test is performed to check if the drive belt tensioner is working properly. If the drive belt tensioner is not working properly, it will not be able to provide the proper tension on the belt to prevent it from slipping, which can cause a squealing noise.
6. This test checks to see if the drive belt is too long, which could prevent the drive belt tensioner from working properly. If the drive belt is installed at the wrong length, it will not be routed properly through the pulleys and the accessory drive component may rotate in the wrong direction.
7. Misalignment of accessory drive pulleys may be caused by improper installation of the pulley or accessory drive component, or the pulley may have been bent during a previous repair. Check the alignment of the pulleys by placing a straight edge in the grooves of two or three pulleys. If a misaligned pulley is found, check the installation and removal procedures for that accessory drive pulley.
8. Inspect the accessory drive pulleys to ensure they are the correct diameter or width. Compare the accessory drive pulleys with those installed on a known good vehicle.
| Step | Operation | Values | Yes | No |
| 1 |
Have you reviewed the diagnostic information Symptoms - Engine Mechanical and performed the necessary inspections?
|
-
|
Jump to operations 2
|
Go to item Symptoms - Engine Mechanical
|
| 2 |
Make sure there is a squealing sound.
Does the engine make a squealing sound?
|
-
|
Jump to operations 3
|
Go to Diagnostic Information
|
| 3 |
Is the whistling sound still present?
|
-
|
Jump to operations 4
|
|
| 4 |
Check accessory drive bearings for free rotation or accessory components for serviceability.
Has the problem been detected and corrected?
|
-
|
Jump to operations 9
|
Jump to operations 5
|
| 5 |
Inspect the drive belt tensioner to ensure it is operating properly. See Drive Belt Tensioner Diagnosis.
Has the problem been detected and corrected?
|
-
|
Jump to operations 9
|
Jump to operations 6
|
| 6 |
Check if the drive belt is the correct length.
Has the problem been detected and corrected?
|
-
|
Jump to operations 9
|
Jump to operations 7
|
| 7 |
Check the alignment of the pulleys.
Has the problem been detected and corrected?
|
-
|
Jump to operations 9
|
Jump to operations 8
|
| 8 |
Check that the pulleys are the correct size.
Has the problem been detected and corrected?
|
-
|
Jump to operations 9
|
-
|
| 9 |
Is the screeching sound still present?
|
-
|
-
|
The system is normal
|
[The source of the article is available on the website «chevyman»]