Why Do my Engine Belts Squeal?

Have your friends nicknamed your car screeches?  Do you park in front of a different apartment building so when you start your car up in the morning and it makes an obnoxious squeaking noise your neighbors won’t know it’s your car?

Having a vehicle with squeaking or squealing engine belts can be embarrassing and annoying.  The terrible noise is also an indication that your engine belt will likely not last much longer and could leave you stranded and your car broken down.

The belt or belts on your engine are used to transfer the rotational energy of your vehicle’s engine to turn any accessories you also want to be powered by your engine.  Some of those accessories are essential for your engine to continue to run like the alternator or the water pump.  Some of the accessories are just for convenience like the AC compressor or power steering pump.  Either way, the belts in your vehicle are important.  Vehicles today either have multiple accessory belts where smaller belts are used and a single belt will only run 1 or 2 accessories with 3 or 4 total belts running off the crank pulley.  This is a safe combination because if 1 belt breaks, often the others will not.  Hopefully you will be able to get your vehicle to safe place without being stranded.  The other belt setup is called a serpentine belt meaning one larger belt runs all the accessories and runs in a serpentine route between and around all the pulleys.  In both cases the belt has to be at the proper tension to work properly.  If the belt is too tight it will create extra resistance in your motor, wear out pulley bearings too fast and could cause the belt to stretch or break quickly.  On the other hand, if the belt is too loose it can slip off or slide on the pulley not transfer the proper power to the accessory.

Your engine belts make a screech or squeal noise usually because the rubber belt is slipping on the metal pulley and just like your tires spinning on the road, this causes noise.  The belt may be slipping due to improper tension or because it simply has gotten old and the surface has become glazed, cracked or brittle.

If you believe your belt may be old or in need of replacement, consider doing the job yourself.  Replacement belts are usually relatively inexpensive and easily accessible on the front of your engine.  Check your vehicle’s manual for instructions on how often to change your engine accessory belt or belts.

If you believe your belt may just be improperly tensioned you can try to adjust the tension yourself.  Most serpentine or single belt systems use an automatic belt tensioner which is just an idler pulley on a spring loaded arm.  The spring tension causes torque on the arm of the idler pulley which pushes on the belt and should keep it at the proper tension.  If your belt tensioner is damaged or the spring has lost its tension replacing it may help restore the proper tension to the belt.  If your belt does not have an automatic belt tensioner, it likely is tensioned by adjusting a non-spring loaded idler pulley or by adjusting one of the accessories itself.

You can look for an adjustment slot and screw on your idler pulley or accessory.  Loosen any nuts or bolts holding the pulley or accessory in place, adjust it until the belt is at the desire tension then re-tighten the bolts.  This is often best done with the help of a friend.  To know when you’re at the proper tension you can use a belt tension measuring tool, or tighten it to the approximate tension of the other belts on your engine.  There is a relatively wide range of acceptable tensions on your accessory belts so check your owner’s manual for the proper range.

Don’t let your vehicle’s squealing or screeching continue to be an embarrassment to you.  Have the confidence to change or tension your belts today!