For 1990-2009 cars

### Drive Belt Rumbling Diagnosis

#### Diagnostic Aids

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

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

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

### Test Description

The numbers below refer to the steps in 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 that the drive belts are 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 will verify if the rumbling noise is related to the drive belts or not. With the drive belts removed the water pump will not operate and the engine may overheat. Also diagnostic trouble codes (DTCs) may set when the engine is operated with the drive belts removed.

3. Inspect the drive belts to ensure that the drive belts are not the cause of the noise. Small cracks across the ribs of the drive belts will not cause the noise. Belt separation is identified by the plies of the belt separating, this may be seen at the edge of the belt or felt as a lump in the belt.

4. Small amounts of pilling is a normal condition and acceptable. When the pilling is extreme the drive belts 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 belts or pulleys.

• | Rumbling may be caused from:

- | Pilling, the accumulation of rubber dust that forms small balls (pills) or strings in the drive belts pulley groove.

- | The separation of the drive belts.

- | 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 belts. Refer to Drive Belt Replacement - Accessory or Air Conditioning Compressor Belt Replacement.
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 or Upper Engine Noise, Regardless of Engine Speed or Lower Engine Noise, Regardless of Engine Speed.

Go to Step 4

4 | Inspect the drive belts for damage, separation, or sections of missing ribs. Refer to Drive Belt Replacement - Accessory or Air Conditioning Compressor Belt Replacement. Were any of these conditions found? | Go to Step 7 | Go to Step 5
5 | Inspect for extreme 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 belts. Refer to Drive Belt Replacement - Accessory or Air Conditioning Compressor Belt Replacement.

Did you complete the repair?

Go to Step 8

Go to Step 7

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

### Drive Belt Vibration Diagnosis

#### Diagnostic Aids

The accessory drive components may have an affect on engine vibration. An overcharged air conditioning (A/C) system, a power steering system restriction, or the incorrect fluid, or an extra load placed on the alternator are suggested items to inspect. 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 steps in the diagnostic table.

1. This test is to verify that the vibration 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 belts or accessory drive components may be causing the vibration. Remove the drive belts and operate the engine for a few seconds, this will verify if the vibration is related to the drive belts or not. With the drive belts removed the water pump will not operate and the engine may overheat. Also diagnostic trouble codes (DTCs) may set when the engine is operated with the drive belts removed.

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

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

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

6. Accessory drive component brackets that are bent, cracked, or loose may put an 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 |

1. Remove the drive belts. Refer to Drive Belt Replacement - Accessory or Air Conditioning Compressor Belt Replacement .
2. Operate the engine for no longer than 30 - 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 belts for wear, damage, debris build-up and missing drive belt ribs. Refer to Drive Belt Replacement - Accessory or Air Conditioning Compressor Belt Replacement . Were any of these conditions found? | Go to Step 5 | Go to Step 6
5 | Install new drive belts. Refer to Drive Belt Replacement - Accessory or Air Conditioning Compressor Belt Replacement . Did you complete the replacement? | Go to Step 11 | --
6 | Inspect for incorrect, loose or missing fasteners. Were any of these conditions found? | Go to Step 7 | Go to Step 8
7 |

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

Were the fasteners replaced and/or tightened?

Go to Step 11

--

8 | Inspect for a bent water pump drive shaft. Refer to Water Pump Cleaning and Inspection . Did you find and correct the condition? | Go to Step 11 | Go to Step 9
9 | Inspect for a bent or cracked accessory drive brackets. Did you find and correct the condition? | Go to Step 10 | --
10 | Replace the bent and/or cracked accessory drive brackets. Refer to Compressor Mounting Bracket Replacement . Refer to Generator Bracket Replacement . Was the bent and/or cracked accessory drive brackets replaced? | Go to Step 11 | --
11 |

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

Does the vibration still exist?

--

System OK