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Test Description

WARNING: This page is about a different car, the 2004 GMC Sierra, 2004 GMC Cab & Chassis Sierra, 2004 Chevrolet Silverado, and 2004 Chevrolet Cab & Chassis Silverado. However, it is still accessible from the selected car via links, so may be relevant.

The number(s) below refer to the step(s) on the diagnostic table.

  1. 2:  This test is to verify that the symptom is present during diagnosing. Other vehicle components may cause a similar symptom.
  2. 3:  This test is to verify that the drive belt is causing the rumbling. Rumbling may be confused with an internal engine noise due to the similarity in the description. Operate the engine for a few seconds, this will verify if the rumbling noise is related to the drive belt or not. With the drive belt removed the cooling fan will not operate and the engine may overheat. Also diagnostic trouble codes (DTCs) may set when the engine is operated with the drive belt removed.
  3. 4:  Inspect 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 will 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. 5:  Small amounts of pilling is a normal condition and acceptable. When the pilling is severe, the drive belt does not have a smooth surface for proper operation.
Drive Belt Rumbling Diagnosis

Step Action Yes No
NOTE: Refer to Belt Dressing Notice in Cautions and Notices.
DEFINITION:
  • A low pitch tapping, knocking, or thumping noise heard at or just above idle.
  • Heard once per revolution of the drive belt or a pulley(s).
  • 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 diagnostic information, 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 .
  2. Operate the engine for no longer than 30 to 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.
Were any of these conditions found?		 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 pulley(s) using a suitable wire brush.
  2. Install the drive belt. Refer to Drive Belt Replacement .
Did you complete the repair?		 Go to Step 8  -
7 Install a new drive belt. Refer to Drive Belt Replacement .
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
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