Possible Causes
• Low belt tension …MOST COMMON
• Low installation tension (locked center drives), belt stretch, extreme belt wear, tensioner spring degradation, belt too long, etc….
• High accessory/idler loading
• Seized bearings, accessory failure/lock-up, ….
• Contamination/Environment
• Fluid contamination on the belt (such as oil, antifreeze, P/S fluid, Belt Dressing, …)
• A hard splash of water such that the belt hydroplanes and looses traction

Possible Solutions
• Belts installed on fixed-center drives should be properly tensioned during installation (35 lbf per rib), and then re-tensioned after ~5 minutes of run-in (30 lbf per rib). If after running for a time the belt falls below 15 lbf per rib, it should again be re-tensioned (30 lbf per rib).
• On systems equipped with an automatic tensioner, the tensioner pulley should turn freely without binding, and the tensioner arm should move smoothly through its entire range of motion.
• While the belt is removed, inspect all accessory pulleys and idlers to insure free and smooth rotation. If there is binding or rough rotation (dry bearing), then the pulley and/or accessory should be replaced.
• If the belt is contaminated with any engine fluid (other than washer fluid), the belt should be replaced.
• The belt should NEVER be sprayed with belt dressing or cleaned with brake cleaner, as this only temporarily eliminates the noise by lubricating the surface. The noise will come back, and typically louder than before.