When diagnosing serpentine accessory drive belts, small cracks that run across the ribbed surface of the belt from rib to rib (1), are considered normal. These are not a reason to replace the belt. However, cracks running along a rib (not across) (2) are not normal. Any belt with cracks running along a rib must be replaced. Also replace the belt if it has excessive wear, frayed cords or severe glazing.
Refer to the ACCESSORY DRIVE BELT DIAGNOSIS CHART for further belt diagnosis.
Noises generated by the accessory drive belt are most noticeable at idle. Before replacing a belt to resolve a noise condition, inspect all of the accessory drive pulleys for alignment, glazing, or excessive end play.
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CONDITION
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POSSIBLE CAUSES
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CORRECTION
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RIB CHUNKING (One or more ribs has separated from belt body) |
1. Foreign objects imbedded in pulley grooves. |
1. Remove foreign objects from pulley grooves. Replace belt. |
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2. Installation damage |
2. Replace belt |
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RIB OR BELT WEAR |
1. Pulley misaligned |
1. Align pulley(s) |
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2. Abrasive environment |
2. Clean pulley(s). Replace belt if necessary |
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3. Rusted pulley(s) |
3. Clean rust from pulley(s) |
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4. Sharp or jagged pulley groove tips |
4. Replace pulley. Inspect belt. |
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5. Belt rubber deteriorated |
5. Replace belt |
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BELT SLIPS |
1. Belt slipping because of insufficient tension |
1. Adjust tension (2.5L) |
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2. Belt or pulley exposed to substance that has reduced friction (belt dressing, oil, ethylene glycol) |
2. Replace belt and clean pulleys |
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3. Driven component bearing failure (seizure) |
3. Replace faulty component or bearing |
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4. Belt glazed or hardened from heat and excessive slippage |
4. Replace belt. |
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LONGITUDAL BELT CRACKING |
1. Belt has mistracked from pulley groove |
1. Replace belt |
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2. Pulley groove tip has worn away rubber to tensile member |
2. Replace belt |
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"GROOVE JUMPING" (Belt does not maintain correct position on pulley) |
1. Belt tension either too low or too high |
1. Replace accessory drive belt tensioner
(Refer to 7 - COOLING/ACCESSORY DRIVE/BELT TENSIONERS - REMOVAL) |
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2. Pulley(s) not within design tolerance |
2. Replace pulley(s) |
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3. Foreign object(s) in grooves |
3. Remove foreign objects from grooves |
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4. Pulley misalignment |
4. Align component |
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5. Belt cordline is broken |
5. Replace belt |
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BELT BROKEN (Note: Identify and correct problem before new belt is installed) |
1. Excessive tension |
1. Replace belt and adjust tension to specification |
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2. Tensile member damaged during belt installation |
2. Replace belt |
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3. Severe misalignment |
3. Align pulley(s) |
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4. Bracket, pulley, or bearing failure |
4. Replace defective component and belt |
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NOISE (Objectionable squeal, squeak, or rumble is heard or felt while drive belt is in operation) |
1. Belt slippage |
1. Replace accessory drive belt tensioner
(Refer to 7 - COOLING/ACCESSORY DRIVE/BELT TENSIONERS - REMOVAL) |
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2. Bearing noise |
2. Locate and repair |
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3. Belt misalignment |
3. Align belt/pulley(s) |
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4. Belt to pulley mismatch |
4. Install correct belt |
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5. Driven component induced vibration |
5. Locate defective driven component and repair |
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6. System resonant frequency induced vibration |
6. Vary belt tension within specifications. |
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TENSION SHEETING FABRIC FAILURE (Woven fabric on outside, circumference of belt has cracked or separated from body of belt) |
1. Tension sheeting contacting stationary object |
1. Correct rubbing condition |
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2. Excessive heat causing woven fabric to age |
2. Replace belt |
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3. Tension sheeting splice has fractured |
3. Replace belt |
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CORD EDGE FAILURE (Tensile member exposed at edges of belt or separated from belt body) |
1. Excessive tension |
1. Replace accessory drive belt tensioner
(Refer to 7 - COOLING/ACCESSORY DRIVE/BELT TENSIONERS - REMOVAL) |
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2. Belt contacting stationary object |
2. Replace belt |
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3. Pulley(s) out of tolerance |
3. Replace pulley |
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4. Insufficient adhesion between tensile member and rubber matrix |
4. Replace belt and adjust tension to specifications |