Diagnosis And Testing - Accessory Drive Belt
| 1 - NORMAL CRACKS BELT OK |
| 2 - NOT NORMAL CRACKS REPLACE BELT |
When diagnosing serpentine drive belts, small cracks that run across ribbed surface of belt from rib to rib, are considered normal. These are not a reason to replace belt. However, cracks running along a rib (not across) are not normal. Any belt with cracks running along a rib must be replaced. Also replace belt if it has excessive wear, frayed cords or severe glazing.
Refer to for further belt diagnosis.
SERPENTINE DRIVE BELT DIAGNOSIS CHART
| CONDITION | POSSIBLE CAUSES | CORRECTION |
|---|---|---|
| RIB CHUNKING (ONE OR MORE RIBS HAS SEPARATED FROM BELT BODY) | 1. Foreign objects imbedded in pulley grooves. | 1. Remove the foreign objects from pulley grooves. Replace the belt. |
| 2. Installation damage. | 2. Replace the belt. | |
| RIB OR BELT WEAR | 1. Pulley(s) misaligned. | 1. Align the pulley(s). |
| 2. Abrasive environment. | 2. Clean pulley(s). Replace the belt if necessary. | |
| 3. Rusted pulley(s). | 3. Clean the rust from pulley(s). | |
| 4. Sharp or jagged pulley groove tips. | 4. Replace the pulley. | |
| 5. Rubber deteriorated. | 5. Replace the belt. | |
| LONGITUDINAL BELT CRACKING (CRACKS BETWEEN TWO RIBS) | 1. Belt has mistracked from pulley groove. | 1. Replace the belt. |
| 2. Pulley groove tip has worn away rubber to tensile member. | 2. Replace the belt. | |
| BELT SLIPS | 1. Belt slipping because of insufficient tension. | 1. Replace the automatic belt tensioner. |
| 2. Belt routed incorrectly. | 2. Verify the belt routing. | |
| 3. Incorrect belt. | 3. Replace the belt. | |
| 4. Belt or pulley subjected to substance (belt dressing, oil ethylene glycol) that has reduced friction. | 4. Replace the belt and clean the pulleys. | |
| 5. Driven component bearing failure. | 5. Replace the faulty component bearing. | |
| 6. Belt glazed and hardened from heat and excessive slippage. | 6. Replace the belt. | |
| "GROOVE JUMPING" (BELT DOES NOT MAINTAIN CORRECT POSITION ON PULLEY) | 1. Belt tension either too high or too low. | 1. Replace the automatic belt tensioner. |
| 2. Belt routed incorrectly. | 2. Verify the belt routing. | |
| 3. Incorrect belt. | 3. Replace the belt. | |
| 4. Pulley(s) not within design tolerance. | 4. Replace the pulley(s). | |
| 5. Foreign object(s) in grooves. | 5. Remove the foreign objects from grooves. | |
| 6. Pulley misalignment. | 6. Check and/or replace. | |
| 7. Belt cord line is broken. | 7. Replace the belt. | |
| BELT BROKEN (NOTE: IDENTIFY AND CORRECT PROBLEM BEFORE NEW BELT IS INSTALLED) | 1. Excessive tension. | 1. Replace the belt and automatic belt tensioner. |
| 2. Incorrect belt. | 2. Replace the belt. | |
| 3. Tensile member damaged during belt installation. | 3. Replace the belt. | |
| 4. Severe misalignment. | 4. Check and replace. | |
| 5. Bracket, pulley, or bearing failure. | 5. Replace the defective component and belt. | |
| NOISE (OBJECTIONABLE SQUEAL, SQUEAK, OR RUMBLE IS HEARD OR FELT WHILE DRIVE BELT IS IN OPERATION) | 1. Belt slippage. | 1. Replace the belt or automatic belt tensioner. |
| 2. Bearing noise. | 2. Locate and repair. | |
| 3. Belt misalignment. | 3. Replace the belt. | |
| 4. Belt-to-pulley mismatch. | 4. Install the correct belt. |