Fixing Noisy Belts

Symptoms

Squeak, squeak, squeak.... You hear a squeak or squeal coming from one of the belts all the time, under load, or when the engine is cold.

Causes

An under-tightened, overtightened, or worn out belt.
Missing belt splash guards.
Pulleys have become polished from age.
Misaligned or bent pulley.

Diagnosis

Use this procedure to figure out which belt is causing the problems:

If the belt squeaks during acceleration or under electrical load (headlights, rear defroster, etc.), then it is likely to be the alternator belt. If the belt squeaks when turning, then it is likely the power steering belt. If the belt squeaks when the air conditioning or defroster is on, then it is likely the air conditioner compressor belt. If the belt squeaks or squeals in the rain or when you drive through a puddle, then you may be missing the plastic pulley splash guard. Tighten any belt that is loose or replace if it is worn or cracked using the information on the Drive Belt Replacement page. If the belt still squeaks during idle, then proceed to step two.
WARNING: it is very dangerous to work around engine belts with the engine running, so proceed at your own risk. Start the engine under which ever conditions the belt squeaks (when hot or cold, etc.). Using a regular bar of hand soap (without pumice) let the bar of soap rub the inside of each belt being very careful not to allow fingers, sleeves, watches, etc get caught (roll up your sleeves and take off any jewelery). When you find a belt that stops squeaking, then you know it is the one. If the belt seems tight and is not badly worn or cracked, then the belt may be too tight. Check your service manual for belt tightening specifications. It is easy to over tighten the timing belt, air conditioner compressor belt, and the alternator belt, so be sure not to. See the belt tension chart on the Drive Belt Replacement page.
If you tried each belt and the squeaking persists, then it is probably the timing belt. See The Timing Belt Squeak section.

The Timing Belt Squeak

Usually what happens is the timing belt idler pulley (towards the rear of the engine) that is used to tighten the belt gets polished over time. If the belt is also over tightened, a persistent squeak will result. To remedy this, you will need to take off the timing belt and you might as well replace it. See the Engine Timing and Belt Replacement page for more details.
Once you have removed the belt, you can deglaze the idler pulley with a piece or emery cloth. Just "sand" the pulley with the cloth until it looks uniformly hazy. You can also deglaze the sprockets to ensure that they are not glazed, but this takes more time and they usually aren't the cause of the squeak. It is a good idea to wipe the teeth and grooves of the sprockets down with a solvent to remove any oil or rubber deposits.
Reassemble and time the engine using the procedure on the Engine Timing and Belt Replacement page.

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Updated 10/30/2003.