Drive Belts, Mounts, Brackets and Accessories: Testing and Inspection

The following are symptomatic noises of the accessory drive belt system:

Chirping
- A high pitched noise that is usually heard once per revolution of a pulley or a belt.
- It is most common on cold, damp mornings.
- Verify this condition by squirting water onto the belt. The noise will momentarily stop.

Squeal
- A loud screeching noise that is caused by a slipping belt (this is unusual for a multiple ribbed belt).
- The noise occurs when a heavy load is applied to the belt, such as an air conditioning compressor engagement, snapping the throttle, or slipping on a seized pulley.

Knocking
- A low pitch tapping noise caused by belt misalignment.
- This noise occurs on cold start-up at idle.

Whine
- A high pitched continuous noise that may be caused by a failed component bearing.

Faint Cycle Rumbling
- A low frequency noise heard once per revolution of the belt.

Piling
- The random accumulation of rubber dust in the bottom of the multi-ribbed belt grooves.
- A small amount of piling is normal.
- Operation of the drive belt system will not be effected unless the buildup exceeds one third (1/3) of the belt groove depth.

Multiple ribbed, accessory drive belts wear evenly with their pulleys. Unusual wear indicates a correction is needed. The following diagnostic tables will aid in diagnosing drive belt system problems.