SAAB WIS ONLINE

Diagnosis of creaking, squeaking and whining drive belt (A20NFT/LHU)

Diagnosis of creaking, squeaking and whining drive belt (A20NFT/LHU)

Diagnostic tools


• A creaking or squeaking noise may be intermittent due to moisture in the drive belts or pulleys. You may need to spray a small amount of water on the belts in order to reproduce the problem. If it is possible to reproduce the symptom by spraying water on the drive belt then cleaning the pulleys may be a solution.

• If the noise is intermittent, verify the accessory drive components by varying their load and ensuring that they are used to maximum capacity. An overloaded air-conditioning, power steering system with a pinched hose or incorrect fluid, or a faulty alternator, are all components that should be checked.

• A creaking, squeaking or whining noise may be caused by a component on the body or in the suspension that is loose or incorrectly fitted. The noise may also be caused by other objects in the car.

• The drive belts are not causing any whining noise.


Test description

The figures below refer to the steps in the diagnostic table.

2

The noise may not be engine related. This step verifies that the noise is coming from the engine. If the noise is not coming from the engine, do not proceed in this table.

3

The noise may be an internal engine noise. Removing the drive belts one at a time and running the engine briefly verifies that the noise is related to the drive belt. When the drive belt has been removed the water pump may not function and the engine may overheat. Diagnostic trouble codes may also be generated when the engine is running with drive belts removed.

4

Check all drive belt pulleys with regard to unravelling. Unravelling involves small balls or clumps, or also strings, in the drive belt grooves due to the accumulation of rubber dust.

6

Misaligned pulleys can be caused by the incorrect installation of accessory drive components, incorrect installation of an accessory drive component pulley or the pulley being bent inwards or outwards in a previous repair. Test if a pulley is misaligned with the help of a straightening plate in the pulley grooves over two or three pulleys. If a misaligned pulley is identified, see the related accessory drive component for the correct installation procedure for the pulley.

10

Checking the fasteners can exclude the possibility that an incorrect screw, nut, spacer or washer has been fitted.

12

When checking whether the pulley is bent you should also check for any dents or other damage to the pulleys. This could cause the drive belt not to be seated correctly in all the grooves or on the smooth surface of a pulley when the rear of the belt is used to drive the pulley.

14

This test verifies that the drive belt tensioner is working properly. If the drive belt tensioner is not working correctly then the correct belt tension to prevent the belt slipping may not be achieved, which may cause a squeaking noise.

15

This test verifies that the drive belt is too long. This could cause the drive belt tensioner to work incorrectly. If a belt of incorrect length is fitted then it may have been routed incorrectly and may turn an accessory drive component in the wrong direction.

16

Misaligned pulleys can be caused by the incorrect installation of accessory drive components, incorrect installation of an accessory drive component pulley or the pulley being bent inwards or outwards in a previous repair. Test if a pulley is misaligned with the help of a straightening plate in the pulley grooves over two or three pulleys. If a misaligned pulley is identified, see the related accessory drive component for the correct installation procedure for the pulley.

17

This test verifies that the pulley diameter or width is correct. Use a car that has been found to be satisfactory when comparing pulley sizes.

19

Replacing the drive belt when it is not damaged or when there is not much unravelling is only a temporary solution.

Stage Event Yes No
DEFINITION: The following items are indications of creaking:
• A loud noise that is heard once per revolution of the drive belt or pulley.

• Creaking may occur when starting in cold and damp weather, and stops when the car reaches normal operating temperature.


DEFINITION: The following items are indications of a squeaking drive belt:
• A loud whistling noise caused by a slipping drive belt. This is unusual for a belt with several ribs.

• The noise is generated when the belt is exposed to heavy loads, e.g. activating an air conditioning compressor or slipping for a pulley that jams or a defective accessory drive component.


DEFINITION: The following items are indications of a whining drive belt:
• A continuous noise with high tone.

• The noise may be caused by a faulty bearing for an accessory drive component.


1 Did you go through the Symptoms for drive belt, and did you carry out the necessary checks? Go to Step 2 Go to "Symptoms - Engine mechanics"
2 Verify that a creaking, squeaking or whining noise is being generated. Does the creaking, squeaking or whining noise come from the engine? Go to Step 3 Go to Diagnostic tools
3
1. Remove the drive belt.

If the engine has several drive belts, remove them one belt at a time and perform the test below each time a belt has been removed.

2. Do not run the engine for longer than 30-40 seconds.

3. Repeat this test if necessary by removing the remaining belt(s).


Can you still hear the creaking, squeaking or whining noise? 		Go to "Symptoms - Engine mechanics" Go to Step 4
4 When diagnosing a creaking noise, check whether there is significant unravelling exceeding 1/3 of the belt groove's depth. When diagnosing a whining or whistling noise, proceed to Step 13. Is there any unravelling in the belt grooves? Go to Step 5 Go to Step 6
5
Clean the drive belt pulleys with a suitable wire brush. Have you completed the repair? Go to Step 20 Go to Step 6
6 Check whether the pulleys are misaligned. Is any one of the pulleys misaligned? Go to Step 7 Go to Step 8
7
Replace or repair all misaligned pulleys. Have you completed the repair? Go to Step 20 Go to Step 8
8
Check whether there are any brackets which are bent or cracked. Are there any brackets that are bent or cracked? Go to Step 9 Go to Step 10
9
Replace all bent or cracked brackets. Have you completed the repair? Go to Step 20 Go to Step 10
10 Check for defective, loose or missing fasteners. Did you identify the condition? Go to Step 11 Go to Step 12
11

1. Tighten all loose fasteners. Information is available in Tightening specifications for fasteners (A20NFT/LHU) .

2. Replace all defective or missing fasteners.


Have you completed the repair? 		Go to Step 20 Go to Step 12
12 Check if the pulley is bent. Did you identify the condition? Go to Step 18 Go to Step 19
13 Check for binding bearings for accessory drive components or a defective accessory drive component. When diagnosing a whining sound and the condition persists, proceed to Diagnostic tools. Did you identify and correct the condition? Go to Step 20 Go to Step 14
14 Test that the drive belt tensioner is working correctly. Information is available in Diagnosis of drive belt tensioner A20NFT/LHU . Did you identify and correct the condition? Go to Step 20 Go to Step 15
15 Check that the drive belt's length is correct. Did you identify and correct the condition? Go to Step 20 Go to Step 16
16 Check whether the pulley is misaligned. Did you identify and correct the condition? Go to Step 20 Go to Step 17
17 Check that the pulley's size is correct. Did you identify and correct the condition? Go to Step 20 Go to Diagnostic tools
18
Replace the bent pulley. Have you completed the repair? Go to Step 20 Go to Step 19
19 Replace the drive belt. See Drive belt, auxiliaries (poly-V) . Have you completed the repair? Go to Step 20 Go to Diagnostic tools
20
Use the system to check the repair. Did you correct the condition? System OK Go to Step 3