Initial Inspection and Diagnostic Overview

Accessory Drive

Inspection and Verification

NOTICE: Under no circumstances should the accessory drive belt, tensioner or pulleys have any fluids or belt dressing applied to them as damage to the belt material and tensioner damping mechanism may occur.

1. Verify the customer concern by operating the system.

2. Visually inspect for obvious signs of mechanical damage.

Visual Inspection Chart






Belt Tensioner With Belt Length Indicator

NOTE: Belt tensioner is shown in the free-state position against the arm travel stops.

NOTE: 6.2L engine accessory drive belt tensioner shown, other accessory drive belt tensioners similar.










3. Check that the belt length indicator, if equipped, on the belt tensioner is in the acceptable belt installation and wear range. If the indicator is in the belt replacement range, either an incorrect belt is installed or the belt is worn beyond the service limit. Install a new belt as necessary.

4. Eliminate all other non-belt related noises that could cause belt misdiagnosis, such as A/C compressor engagement chirp, A/C slugging noise, power steering cavitations at low temperatures, Variable Camshaft Timing (VCT) tick or generator whine.

5. If a concern is found, correct the condition before proceeding to the next step.

V-Ribbed Serpentine Drive Belt With Cracks Across Ribs





6. Check the belt for cracks. Up to 15 cracks in a rib over a distance of 100 mm (4.0 in) can be considered acceptable. If cracks exceed this standard, install a new belt.

V-Ribbed Serpentine Belt With Piling

NOTE: Piling is an excessive buildup in the V-grooves of the belt.





7. The condition of the V-ribbed drive belt should be compared against the illustration and appropriate action taken.
1. Small scattered deposits of rubber material. This is not a concern, therefore, installation of a new belt is not required.

2. Longer deposit areas building up to 50% of the rib height. This is not considered a durability concern, but it can result in excessive noise. If noise is apparent, install a new belt.

3. Heavy deposits building up along the grooves resulting in a possible noise and belt stability concern. If heavy deposits are apparent, install a new belt.


V-Ribbed Serpentine Belt With Chunks of Rib Missing





8. There should be no chunks missing from the belt ribs. If the belt shows any evidence of this, install a new accessory drive belt.

9. If the concern is not visually evident, verify the symptom and GO to Symptom Chart. Symptom Related Diagnostic Procedures