GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2004 🢒 Isuzu - N Series 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 Drive Belt Rumbling Diagnosis

Diagnostic Aids

Vibration from the engine operating may cause a body component or another part of the vehicle to make rumbling noise.

The drive belt may have a condition that cannot be seen or felt. Sometimes replacing the drive belt may be the only repair for the symptom.

If, after replacing the drive belt and completing the diagnostic table, the rumbling is only heard with the drive belt installed, there may be an accessory drive component failure. Varying the load on the accessory drive component may aid in identifying which component is causing the rumbling noise.

Test Description

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

  1. This step verifies that the symptom is present during diagnosis. Other vehicle components may cause a similar symptom.

    2.

  2. This step verifies that the drive belt is causing the rumbling. Rumbling may be confused with an internal engine noise due to the similarity in the description. Remove only one drive belt at a time, if the vehicle has multiple drive belts. Operate the engine for a few seconds, this verifies if the rumbling noise is related to the drive belt or not. With the drive belts removed, the water pump does not operate and the engine may overheat. Diagnostic trouble codes (DTCs) may set when the engine is operated with the drive belt removed.

    3.

  3. This step inspects the drive belt to ensure that the drive belt is not the cause of the noise. Small cracks across the ribs of the drive belt does not cause the noise. Belt separation is identified by the plys of the belt separating. This may be seen at the edge of the belt or felt as a lump in the belt.

    4.

  4. Small amounts of pilling is an acceptable, normal condition. When the pilling is severe, the drive belt does not have a smooth surface required for proper operation.

Step

Action

Yes

No

Notice: Refer to Belt Dressing Notice in the Preface section.

DEFINITION:

    • A low pitch tapping, knocking or thumping noise heard at or just above idle.
    • Heard once per revolution of the drive belt or pulley.
    • Rumbling may be caused from:
       - Pilling, the accumulation of rubber dust that forms small balls, pills, or strings in the drive belt pulley groove
       - The separation of the drive belt
       - A damaged drive belt

1

Did you review the Symptoms - Engine Mechanical and perform the necessary inspections?

Go to Step 2

Go to Symptoms - Engine Mechanical

2

Verify that there is a rumbling noise.

Does the engine make the rumbling noise?

Go to Step 3

Go to Diagnostic Aids

3

  1. Remove the drive belt. Refer to Drive Belt Replacement - Accessory or Drive Belt Replacement - Air Conditioning.
  2. Operate the engine for no longer than 30-40 seconds.

Does the rumbling noise still exist?

Go to Engine Noise on Start-Up, but Only Lasting a Few Seconds

Go to Step 4

4

Inspect the drive belt for damage, separation or sections of missing ribs.

Did you find any of these conditions?

Go to Step 7

Go to Step 5

5

Inspect for severe pilling of more than 1/3 of the drive belt groove depth.

Do the drive belt grooves have pilling?

Go to Step 6

Go to Step 7

6
  1. Clean the drive belt pulleys, using a suitable wire brush.
  2. Install the drive belt. Refer to Drive Belt Replacement - Accessory or Drive Belt Replacement - Air Conditioning.

Did you complete the repair?

Go to Step 8

--

7

Install a new drive belt. Refer to Drive Belt Replacement - Accessory or Drive Belt Replacement - Air Conditioning.

Did you complete the replacement?

Go to Step 8

--

8
  1. Clear any codes.
  2. Run the engine in order to verify the repair.

Does the rumbling noise still exist?

--

System OK