Drive Belt: Testing and Inspection

DRIVE BELT DIAGNOSIS
Drive belts and pulleys wear evenly with use. Unusual signs of wear indicate some correction is needed. This diagnostic chart will aid in diagnosing multiple ribbed belt system problems.

Definitions:
Chirping: A high pitched noise that is usually heard once per revolution of a pulley or belt. It is also usually heard, at idle and is most common on cold damp mornings. By squirting water onto a chirping belt, the noise will momentarily go away.
Squeal: A loud screeching noise that is usually caused by a slipping belt. The noise usually occurs when a heavy load is applied to the belt, such as compressor engagement, accelerating the seized pulley.
Whine: A high pitched continuous noise that may be caused by a failed bearing.
Faint Cyclic Rumbling: A deep low frequency noise (once per revolution of the belt).
Pilling: The random accumulation of rubber dust in the bottom of the multi-ribbed belt grooves. A small amount pilling is normal. Operation of the drive belt system will not be affected unless buildup exceeds 1/3 of the belt groove depth.





Physical Inspection
^ Check the drive belt for looseness, damage, or fabric delamination. If the belt is loose, check the belt tensioner for proper operation. The belt tensioner is not adjustable. If it is not working properly, it must be replaced. If the belt is delaminated or damaged, replace it.

NOTE: Cracks across the rib material are a normal part of the belt aging process. Cracks do not affect belt operation, and do not indicate a need to replace it.

^ Check the belt length scale on the tensioner. If it reads outside the acceptable range, check for proper routing as shown on the belt routing label and in this section. Also check for proper tracking of belt ribs in the pulley grooves, correct pulley sizes (including idlers), and correct belt length.

NOTE: Multiple rib belts stretch and wear very little. Normal stretch and wear rarely exceeds 10 mm (3/8 inch) on the belt length scale.