When diagnosing serpentine accessory drive belts,
small cracks that run across the ribbed surface of the
belt from rib to rib, are considered normal. These are
not a reason to replace the belt. However, cracks run-
ning along a rib (not across) 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 ACCESSORY DRIVE BELT DIAGNOSIS
CHART for further belt diagnosis.

NOISE 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 pul-
leys for contamination, alignment, glazing, or exces-
sive end play.

BELT ACCESSORY DRIVE

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ACCESSORY 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 foreign objects from
pulley grooves. Replace belt.

2. Installation damage

2. Replace belt

RIB OR BELT WEAR

1. Pulley misaligned

1. Align pulley(s)

2. Abrasive environment

2. Clean pulley(s). Replace belt if
necessary

3. Rusted pulley(s)

3. Clean rust from pulley(s)

4. Sharp or jagged pulley groove
tips

4. Replace pulley. Inspect belt.

5. Belt rubber deteriorated

5. Replace belt

BELT SLIPS

1. Belt slipping because of
insufficient tension

1. Inspect/Replace tensioner if
necessary

2. Belt or pulley exposed to
substance that has reduced friction
(belt dressing, oil, ethylene glycol)

2. Replace belt and clean pulleys

3. Driven component bearing failure
(seizure)

3. Replace component or bearing

4. Belt glazed or hardened from
heat and excessive slippage

4. Replace belt.

LONGITUDAL BELT CRACKING

1. Belt has mistracked from pulley
groove

1. Replace belt

2. Pulley groove tip has worn away
rubber to tensile member

2. Replace belt

GROOVE JUMPING
(Belt does not maintain correct
position on pulley)

1. Incorrect belt tension

1. Inspect/Replace tensioner if
necessary

2. Pulley(s) not within design
tolerance

2. Replace pulley(s)

3. Foreign object(s) in grooves

3. Remove foreign objects from
grooves

4. Pulley misalignment

4. Align component

5. Belt cordline is broken

5. Replace belt

BELT BROKEN
(Note: Identify and correct problem
before new belt is installed)

1. Incorrect belt tension

1. Replace Inspect/Replace
tensioner if necessary

2. Tensile member damaged during
belt installation

2. Replace belt

3. Severe misalignment

3. Align pulley(s)

4. Bracket, pulley, or bearing failure

4. Replace defective component
and belt

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BELT ACCESSORY DRIVE

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