Diagnostic Information
Engine vibration can cause rumbling noise from body components or other parts.
The drive belt may have properties that cannot be determined by visual inspection. Sometimes replacing the belt may be the only way to confirm that the problem is with the belt.
If the entire diagnostic table is completed after the drive belt is replaced, but the rumble is only present when the drive belt is installed, an accessory drive component such as the A/C compressor may be the cause. Varying the load on each accessory drive component in turn should help isolate the component causing the noise.
Description of the test
The item numbers below are the step numbers in the diagnostic table.
- Confirms the existence of a symptom at the time of diagnosis. Noise may be caused by other vehicle components.
- Confirms that the accessory drive belt is causing the noise. Drive belt rumble is often confused with internal engine noise due to the similarity in the description. 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.
- Inspection of the drive belt will ensure that it is not the cause of the noise. Small cracks in the ribs of the drive belt do not cause noise and are not in themselves a justification for replacing the belt. Belt delamination can be identified by the layer of belt separation and can be seen along the side edges of the belt or felt as bulges under the belt.
- A small amount of build-up and inclusions is normal and is considered acceptable. When the amount of pilling reaches a significant level (33% of belt groove depth), the belt does not leave a smooth working surface and needs to be replaced.
Diagnostic table
Definition: Accessory drive belt rumble can be defined as a low-pitched thud, thump, or thud heard only at or above idle speed, once per revolution of the drive belt or specific accessory drive component. Drive belt rumble is caused by one of the following:
- balls or strips in the grooves of the drive belt;
- split drive belt or
- Damaged or defective drive belt.
Note: Pilling is the formation of small balls (growths) or strips of rubber in the grooves of the drive belt caused by the accumulation of rubber dust.
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 rumbling 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 rumbling sound still present?
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-
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The drive system of the aggregates is in order.
Go to "Symptoms" and restart diagnostics
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Go to operation 4
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4 |
Inspect the accessory drive belt for damage, splitting, or missing ribs.
Are there any damage, delamination, or missing ribs?
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-
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Jump to Operation 7
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Go to operation 5
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5 |
Inspect accessory drive belt for severe pilling (exceeding 33% of the belt groove depth).
Is serious peeling detected?
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-
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Go to operation 6
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Go to operation 5
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6 |
Clean the drive belt with a suitable wire brush and reinstall on the motor, see Section 1B, Engine Mechanical - 2.0 Diesel.
Has the repair been completed?
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-
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Jump to operation 8
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-
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7 |
Install a new accessory drive belt, see Section 1B, Engine Mechanical - 2.0 Diesel.
Has the accessory drive belt been replaced?
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-
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Jump to operation 8
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-
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8 |
If required, reinstall the accessory drive belt and operate the system to confirm repair is complete.
Has the rumbling 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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