What Does a Serpentine Belt Do?

A serpentine belt helps keep the car running.

There’s a sound that cars sometimes make. You know the one. It’s that awful high-pitched squeal that alerts everyone within a 10-block radius that there’s something majorly wrong with the vehicle. That disgusting tone is coming from the serpentine belt, which is a closed strip of grooved rubber and metal that is responsible for several vital engine and vehicle functions. It’s turned by the crankshaft pulley and can slip or become damaged over time.

Under your hood, the power steering system, air conditioning, and climate system, water pump, and alternator are all driven by the serpentine belt. When the engine is running, the belt winds its way around pulleys attached to all of those components and operates mostly silently when everything is working properly.

Unfortunately, nothing lasts forever, especially not small pieces of rubber that are constantly in motion. When your serpentine belt starts to fail, it might make that sound we described earlier, or it might just fail and make it nearly impossible to safely steer your car. Either way, Car Bibles’ editors are here to help you understand what’s going on and why it’s happening.

Stick around.

A detached serpentine belt.

What Are The Signs Of A Failing Serpentine Belt?

If your serpentine belt is heading toward failure, your car will tell you about it in several ways. These are the signs to look out for.

Squealing Noise

This is the most noticeable sign of a failing serpentine belt. When the belt starts slipping, it’ll make one of the most annoying sounds you’ve ever heard, and it’s loud. It usually manifests as a squeal, squeak, or screech. The sound may become more pronounced when you first start the vehicle, or when you turn the steering wheel.

Power Steering or Air Conditioning Stop Working

This is more of an issue when the belt breaks, but both the air conditioning system and the power steering system are tied to the serpentine belt. If the belt breaks, the steering wheel could become very hard to turn, making the car much more difficult to control. Air conditioning is a comfort issue, but being able to steer the car is a safety problem.

Cracks Or Damage To The Belt

You should be able to see the serpentine belt under your hood, though some newer cars have plastic covers that will need to be moved to expose the belt. With the car turned off and the engine cool, take a good look at the belt and feel it with your hand to determine if there is damage. If you see cracks or feel that it’s starting to fray or tear, it’s time to take your car to the shop for a replacement. Too much slack isn’t a good sign, either.

What Happens If The Belt Breaks?

If you can help it, it’s best to take care of the belt before it gets to the point of breaking. There are plenty of signs a belt is going bad, and if you’re performing your regular inspections, you should be able to ward off the problem before it fully snaps.

At best, the sudden failure of a serpentine belt can be frightening, but it could also cause a major safety issue. A broken serpentine belt can cause a sudden loss of steering function, or it could make it very difficult to turn the steering wheel.

The serpentine belt is also connected to your car’s water pump and cooling system, so a broken belt will cause a disruption in your car’s ability to cool itself. Finally, a broken belt may also cause other parts of the car to stop working, such as the climate control system, the stereo, headlights, and other electrical components.

If your belt breaks, immediately shut the car off and do not turn it back on until you have replaced the belt.

An attached serpentine belt.

What Will A New Serpentine Belt Cost?

Replacing a serpentine belt, broken, worn, or otherwise, isn’t that expensive. You can count on spending somewhere between $100 and $200 for the repair, depending on the vehicle. Parts generally cost less than $50, so the majority of the repair’s price tag is related to labor. Keep in mind that if you’ve ignored the belt, or if it’s broken and caused damage to other parts of the vehicle, your costs could be higher.

Car Bible’s Glossary for Serpentine Belts

Water Pump

Your car’s water pump is a vital part of the cooling system. It moves water from the radiator to the motor and back again. By doing so, it also helps maintain a constant engine temperature.

Power Steering

Power steering is a system in your vehicle that uses hydraulic power or electric motors to supplement the effort put in by the driver to turn the wheels. This makes it much easier to steer and turn the car at low speeds.

Climate Control System

The climate control system in vehicles refers to the heating, cooling, and air circulation functions. These systems are tied into the operation of the serpentine belt, as they rely on the cooling system and other electrical functions to work properly.


The tensioner is similar to a pulley and helps the serpentine belt maintain a constant level of tension to properly drive all of the various accessories it’s responsible for. This is always something to check, the symptoms you experience might be caused by a failing tensioner, not a bad belt.

Your Questions, Our Answers on Serpentine Belts

Q: Can I Drive With A Broken Serpentine Belt?

A: While it might be physically possible to drive your vehicle with a broken serpentine belt, it’s certainly not a good idea. Remember, that little strip of rubber spinning away under your hood is responsible for everything from the air conditioning system to your ability to turn the steering wheel, so it’s a good idea to take care of issues as they arise.

Q: Does My Car Have More Than One Serpentine Belt?

A: Some vehicles have more than one belt to drive separate functions, but the vast majority of new vehicles on the road today have only one. Older cars are more likely to have multiples, which were simply called drive belts, not serpentine belts.

Q: What Causes The Belt To Break In The First Place?

A: In many cases, it’s just that the belt is old and worn. Though they’re not always prone to break with age, serpentine belts are made of rubber and other flexible materials that can degrade over time due to pressure wear and temperature fluctuation. Another common cause of failing serpentine belts is a malfunction in one of the components that it drives.

Car Bible’s Favorite Serpentine Belt-Related Products

Gates Multi V-Groove Belt
AC Delco Professional V-Ribbed Belt
Crescent 170-Piece General Purpose Tool Set

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Tony Markovich

Tony MarkovichTony has a thing for pop-up headlights. His first car was a $3,000 1996 Saturn SC2 Coupe, and his current project is a 1970 Opel GT junker. When he's not daydreaming about the Cadillac Sixteen, he's watching the Chicago Bulls go undefeated on TNT. Contact the author here.