Serpentine Belt Squeaks

The squeak is a series of high-pitched, intermittent, "rhythmic" sounds. As belt speed increases, the pitch and volume remain constant, which is why you hear a continuous belt squeak when accelerating.

Six Reasons for the Squeak

Pulley misalignment is the number one cause of the noise

Improper installation

Worn belt ribs

Worn pulley bearings causing wobble or excessive free play

Contaminated oil, power steering fluid, antifreeze, or belt dressings

Low-quality belts installed

Solutions for misaligned noises

Check the alignment of all pulleys using a straightedge or laser alignment tool.

Make sure all accessory pulleys and brackets are tight to their mounting surfaces.

Inspect and replace all accessories and pulleys that are difficult to rotate or that exhibit excessive wobble or free play due to rough or seized bearings. Keep in mind that power steering pulleys and worn harmonic balancers can also cause misalignment.

Serpentine Belt Squeaks

The squealing sound is high pitched, lasts for a few seconds, and the volume may change, but the pitch does not.

Top Three Causes of Squealing

Low belt tension can be caused by low installed tension, stretched belts, severely worn belts, degraded tension springs, or belts that are too long.

Excessive accessory/idler drag due to bearing seizure or accessory failure/locking.

Fluid contamination on belts due to exposure to belt dressings, oils, antifreeze, or other chemicals.

Solutions to Tension Squealing

The manual tensioning application should be checked for proper tension (35 pounds per rib) and then re-tensioned (30 pounds per rib) after a 5-minute break-in. This allows the belt to rest on the pulleys.

On vehicles equipped with automatic belt tensioners, the tensioner pulley should turn freely without binding, and the tensioner arm should move smoothly and with adequate tension throughout its range of motion.

Always check the tensioner pulley bearing for noise and wear. Replace the tensioner if the bearing feels rough or the pulley has slipped out.

After removing the belt, check all accessory pulleys and idler pulleys to make sure they rotate freely and smoothly. If dry bearings cause binding or rough rotation, the pulleys and/or accessories should be replaced.

If the belt is contaminated with motor oil, power steering fluid, antifreeze, or any other petroleum-based lubricant, it can weaken EPDM belts and even cause them to swell and make noise. Any serpentine belt that becomes wet with oil must be replaced.

Never attempt to correct the problem by belt trimming.