For 1990-2009 cars

## Drive Belt Rumbling and Vibration Diagnosis Rumble

### Diagnostic Aids

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

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

If replacing the drive belt, completing the diagnostic table, and the noise is only heard when the drive belt is installed, there might be an inoperative accessory drive component. Varying the load on the different accessory drive components may aid in identifying which component is causing the rumbling noise.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This test is to verify that the symptom is present during diagnosing. Other vehicle components may cause a similar symptom.

2. This test is to verify the drive belt is causing the rumbling noise. A rumbling noise may be confused with an internal engine noise due to the similarity in the description. When removing the drive belt the water pump will not be operating and the engine may overheat. Also DTCs may set when the engine is operating with the drive belts removed.

3. Inspecting the drive belt is to ensure that it is not causing the noise. Small cracks across the ribs of the drive belt will not cause the noise. Belt separation is identified by the plies of the belt separating and may be seen at the edge of the belt or felt as a lump in the belt.

4. Small amounts of pilling is normal condition and acceptable. When the pilling is extreme the drive belt does not have a smooth surface for correct 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 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.

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 |

Important: When removing the drive belt the water pump will not be operating and the engine may overheat.

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 Symptoms - Engine Mechanical

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 extreme pilling of more than 1/3 of the drive belt pulley grooves. Did you find extreme 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 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 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Diagnostic Aids

## Drive Belt Rumbling and Vibration Diagnosis Vibration

### Diagnostic Aids

The accessory drive components can have an affect on engine vibration. Such as, but not limited to, the A/C system over charged, the power steering system restricted or the incorrect fluid, or an extra load on the alternator. To help identify an intermittent or an incorrect condition, vary the loads on the accessory drive components.

### Test Description

The numbers below refer to the step numbers on the diagnostic table.

1. This test is to verify that the symptom is present during diagnosing. Other vehicle components may cause a similar symptom such as the exhaust system, or the drivetrain.

2. This test is to verify that the drive belt or accessory drive components may be causing the vibration. When removing the drive belt the water pump will not be operating and the engine may overheat. Also DTCs may set when the engine is operating with the drive belt removed.

3. The drive belt may cause a vibration. While the drive belt is removed, this is the best time to inspect the condition of the belt.

4. Inspecting of the fasteners can address the possibility that a wrong bolt, nut, spacer, or washer was installed.

5. Inspect the water pump shaft for being bent. Also, inspect the water pump bearings for smooth operation and play above acceptable tolerances. Compare the water pump with a known good water pump.

6. Accessory drive component brackets that are bent, cracked, or loose may put extra strain on that accessory component causing it to vibrate.

Step | Action | Yes | No
--- | --- | --- | ---
Notice: Refer to Belt Dressing Notice in the Preface section. 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 diagnostic information, and perform the necessary inspections? | Go to Step 2 | Go to Symptoms - Engine Mechanical .
2 | Verify that the vibration is engine related. Does the engine make the vibration? | Go to Step 3 | Go to Diagnostic Aids
3 |

Important: When removing the drive belt the water pump will not be operating and the engine may overheat.

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

Does the engine still make the vibration?

Go to Drive Belt Rumbling and Vibration Diagnosis

Go to Step 4

4 | Inspect the drive belt for wear, damage, debris build-up and missing drive belt ribs. Did you find any of these conditions? | Go to Step 5 | Go to Step 6
5 | Install a new drive belt. Refer to Drive Belt Replacement . Did you complete the replacement? | Go to Step 10 | -
6 | Inspect for incorrect, loose or missing fasteners. Did you find any of these conditions? | Go to Step 7 | Go to Step 8
7 |

Notice: Refer to Fastener Notice in the Preface section.

1. Tighten any loose fasteners. Refer to Fastener Tightening Specifications .
2. Replace incorrect or missing fasteners.

Did you complete the repair?

Go to Step 10

-

8 | Inspect for a bent water pump shaft. Refer to Water Pump Replacement . Did you find and correct the condition? | Go to Step 10 | Go to Step 9
9 | Inspect for bent or cracked brackets. Did you find and correct the condition? | Go to Step 10 | Go to Diagnostic Aids
10 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3