Drive Belt: Testing and Inspection

Definitions The following are symptomatic noises of the accessory drive belt system:
1. 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.
2. 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.
3. Knocking: A low pitch tapping noise caused by belt misalignment. This noise occurs on cold start-up at idle.
4. Whine: A high pitched continuous noise that may be caused by a failed component bearing.
5. Faint Cycle Rumbling: A low frequency noise heard once per revolution of the belt.
6. Pilling: The random accumulation of rubber dust in the bottom of the multi-ribbed belt grooves. A small amount of pilling 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.

NOTE: 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.