How long has it been since you changed or inspected your serpentine belt? In modern cars, it is one of the most durable parts under the hood, but it still requires replacement when it becomes worn. How do you tell if it is time to put this project on your weekend to-do list?

1. A Visual Check Works on Older Vehicles

If you are driving a car or truck that is older than 10 years, it may still have an older type of rubber used on its serpentine belt. These belt compounds would actually stretch and crack, clearly showing you when it is time for a replacement. The newer belts use a more durable compound that stretches instead of cracking. You will need to use other methods to determine if your belt has turned too many miles.

2. Listening for Squeaks and Squeals

One of the most common indicators of an old belt is that classic squeal. It isn’t because the car is old. The serpentine belt is rubbing against the edges of pulleys, causing the squeak. This is a result of stretching and the belt is no longer riding in the correct path. You most likely need a new belt.

3. Give the Serpentine Belt a Tug

The belt should lay firmly against the tensioner pulley. You should not be able to simply flip it over or pull it off its intended path. If that is the case, order up a replacement belt before it jumps the track and causes some serious havoc under the hood.

4. Rolling the Tensioner Pulley by Hand

Even if your serpentine belt looks fine, if the tensioner pulley has lost grease in its bearings, it could be providing too much resistance to the belt causing undue wear. If the pulley does not roll freely, it should be replaced. Since the tensioner and the belt have the same expected lifespan, replace both of them at the same time for a reliable repair. Any other idler pulleys should also be replaced to maximize the serpentine belt lifespan. Some manufacturers, including MICHELIN, sell these components together as a kit.

5. Put it to the Flex Test

Your serpentine belt should be bendable without creating creases in the belt. If you have the belt off the engine, flip it so the toothed-side is exposed and bend the belt. If you see even minor cracks or stretches, it is time for a new one.

6. Using a Belt Wear Tester on Newer Machines

Since the introduction of longer-lasting compounds for serpentine belts, is it known that they wear differently. Now we check the belts much like we test tires for tread wear. Using a Belt Wear Tester, place it against the teeth of the belt. A new belt will fit snugly around the tool. On a worn-out belt, there is light showing around the teeth of the tester and the tool can be wiggled around. Basically, the belt wears out between the ribs until finally the thinnest part of the belt separates in a catastrophic failure. Believe the tester tool that it is time for a change. The tester only costs a couple of bucks and is available on Amazon.

7. Just How Long will a Serpentine Belt Last?

Most new serpentine belts used on modern cars are designed to last between 80,000 and 100,000 miles. If your older machine suggests a change at 50,000 miles, check the OEM specs for the original belt. If it was manufactured as rubber and replacement parts are constructed out of the older material, 50,000 miles is a good marker. You may find an aftermarket belt built out of the newer compound that will last longer.