Tom's Corner Garage: Squealing Serpentine Belts
This weekly feature for Edmunds Daily about car repair and maintenance is written by Tom Torbjornsen, the popular host of America's Car Show on satellite radio.
Dear Tom,
Why do my car's belts squeal all the time? I own a 2006 Ford Focus with a 2.3 liter 4 cylinder engine. I have replaced the belts three times in the last three months and they still squeal, especially when the A/C is on. I am tired of replacing belts, so what else could be wrong?
Alan from Freehold, NJ
Alan's car has only one drive belt, called a serpentine belt. He should check for a worn, glazed, or torn belt or a worn automatic belt tensioner. Note that Alan keeps referring to "belts." His car only has one that drives all the components, and we'll take a closer look at these serpentine belts.
Why is it called a Serpentine Belt?
This type of system utilizes one long belt to snake its way throughout the pulley system (see illustration, right) driving all the components, hence its name Serpentine (snake).
How do you adjust the belt tension?
Carmakers realized that if they stretched the belt out to the required length needed to drive all the components, then they would have to come up with a way to automatically adjust the belt as it stretched out with wear. The solution is the automatic belt tensioner, which is a spring-loaded idler pulley that rides against the back of the belt and keeps it properly tensioned at all times. As in the case of Alan's car, these tensioners wear out over time and must be replaced. How do you know that the tensioner is worn out? The belt will squeal incessantly; especially when a load (such as the air conditioner) is added to the system.
How do I know when to replace the belt?
A simple visual inspection of the belt will show signs of age, which include glazing, torn ribs, excessive wear, cracking, or fraying. Average serpentine belt life? 35-50,000 miles.
'Til next time...Keep Rollin'
- Posted by
- Paul Seredynski July 15, 2009, 11:00 AM
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- Car Maintenance
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- accessory belts, serpentine belt
Ever heard of a Gates belt making a rhythmic squeal from the painted on logo going through the pulley(s)?
35-50000 miles is incorrect. It's as accurate as a 3000 miles oil change. Most require 100k mile belt changes.
Check your owners manual!
In theory they're supposed to be good for 100K,in real life they get hard and form cracks in the ribs. This often makes them very noisy, and where I live it will not pass safety inspection for licensing. I don't doubt they function to 100K, but I doubt that happens often.
High heat, extreme cold or road salt all really shorten belt life. If you live in a mild climate then they likely will last 100K or more.
If (like most people) you don't live somewhere with a perfect climate and no road salt then you are better off changing them more often. It's cheap insurance against a breakdown.
It took less then 5 minutes for me to change mine and I kept old one as a spare ( I put it in the spare tire compartment) in case the new one snapped on the road.