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Home >> Cadillac >> 2006 >> STS Base, 3.6 7, RWD >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 18 (Engine Mechanical - 4.4L - Introduction) >> Diagnostic Information and Procedures >> Drive Belt Rumbling and Vibration Diagnosis >> Test Description

Test Description

WARNING: This page is about a different variant/trim than selected.

The numbers below refer to the step numbers 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 one of the drive belts is causing the rumbling noise or vibration. Rumbling noise 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. When removing the drive belts the water pump may not be operating and the engine may overheat. Also, diagnostic trouble codes (DTCs) may set when the engine is operating with the drive belt(s) removed.
  3. 4:  Inspecting the drive belts is to ensure that they are not causing 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 and may be seen at the edge of the belt our 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.
  5. 9:  Inspection of the fasteners can eliminate the possibility that the incorrect bolt, nut, spacer, or washer was installed.
  6. 11:  This step should only be performed if the water pump is driven by the drive belt. Inspect the water pump shaft for a bent condition. Also inspect the water pump bearings for smooth operation and excessive play. Compare the water pump with a known good water pump.
  7. 12:  Accessory drive component brackets that are bent, cracked, or loose may put extra strain on that accessory component causing it to vibrate.
Drive Belt Rumbling and Vibration Diagnosis

Step Action Yes No
NOTE: Refer to Fastener Notice .
DEFINITION: The following items are indications of drive belt rumbling:
  • 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.
  • 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
DEFINITION: The following items are indications of drive belt vibration:
  • The vibration is engine-speed related.
  • The vibration may be sensitive to accessory load.
1 Did you review the Symptoms-Engine Mechanical operation and perform the necessary inspections? Go to Step 2  Go to Symptoms - Engine Mechanical 
2  Verify that there is a rumbling noise or that the vibration is engine related.
Does the engine make the rumbling noise or vibration?		 Go to Step 3  Go to Diagnostic Aids
3 
  1. Remove the drive belt(s).

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

  2. Operate the engine for no longer than 30-40 seconds.
  3. Repeat this test if necessary by removing the remaining belt(s).
Does the rumbling or vibration still exist?		 For rumbling diagnosis, go to Symptoms - Engine Mechanical . For vibration diagnosis, go to Vibration Analysis - Engine . Go to Step 4 
4  Inspect the drive belt(s) for wear, damage, separation, sections of missing ribs, and/or debris build-up.
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 pulley grooves.
Did you find severe pilling?		 Go to Step 6  Go to Step 7 
6
  1. Clean the drive belt pulleys using a suitable wire brush.
  2. Reinstall the drive belts.
Did you correct the condition?		 Go to Step 8  Go to Step 7 
7 Install a new drive belt. Refer to Supercharger Belt Replacement , Water Pump and Air Conditioning Compressor and Power Steering Pump Belt Replacement , or Generator Drive Belt Replacement .
Did you complete the replacement?		 Go to Step 8  -
8 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 9 
9  Inspect for improper, loose or missing fasteners.
Did you find any of these conditions?		 Go to Step 10  Go to Step 11 
10
    NOTE: Refer to Fastener Notice .
  1. Tighten any loose fasteners. Refer to Fastener Tightening Specifications .
  2. Replace any improper or missing fasteners.
Did you complete the repair?		 Go to Step 13  -
11  Inspect for a bent water pump shaft.
Did you find and correct the condition?		 Go to Step 13  Go to Step 12 
12  Inspect for bent or cracked accessory brackets.
Did you find and correct the condition?		 Go to Step 13  Go to Diagnostic Aids
13 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 3 
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