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, that awful high-pitched squeal that alerts everyone within a 10-block radius that there’s something majorly wrong. This particular disgusting tone comes from the serpentine belt: a closed strip of grooved rubber and metal responsible for several vital engine and vehicle functions and turned by the crankshaft pulley. 

As for specifics, under your hood, the power steering system, climate systems, 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.
Depositphotos

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 as 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 — as you should! — 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.
Depositphotos

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.

The Job: How To Remove and Replace a Serpentine Belt

The job of replacing a serpentine belt can be complicated, depending on the type of vehicle you’re working on but in most cases, it’s a fairly straightforward process. Accessing the belt itself may prove to be the most difficult part of the whole job, especially if your vehicle’s engine bay is covered by a large plastic cover, as many modern engine bays are.

The Safety Brief

The biggest thing to remember here is security. If you’re going to be working underneath your vehicle for any amount of time, you’ll want to make sure that it’s secure and stable on jack stands.

  • Pay attention to the vehicle position and stability if you’re lifting it on a jack for this job. Don’t leave the vehicle on the jack while working and use jack stands to hold its position.
  • Work on a flat surface as far from traffic as possible. A garage or driveway is ideal, but if you have to do the work outside of one of those locations, it’s best to find a quiet side street or parking lot to do the job.
  • Wear gloves and eye protection for this job. You may be confident in your ability to look away when danger arises, but things can happen and surprises are no fun when you’re not prepared.
  • The serpentine belt is one of the most important components under your hood, so it’s vital that you do the job correctly. If you’re unsure about one or more steps in the process, get help. 
  • If you don’t have one of the required tools for this job, get one, or take your car into the shop. Using tools for jobs they were never intended for can be dangerous.

The Tools and Parts You Need

Replacing your serpentine belt requires quite a few tools, but none are extremely expensive.

Parts

The only part involved in this job is the replacement belt itself, but there are related parts that may be required to complete the job:

Step-by-Step Instructions for Replacing a Serpentine Belt

The exact process to replace your serpentine belt will vary depending on the model of vehicle you have. Some vehicles use manual tensioners and some have automatic tensioners, so it’s important to refer to your vehicle’s service or repair manual to determine the exact process you need to follow.

  1. Locate your serpentine belt

    1. Make sure the vehicle is turned off and is parked in a safe, flat location.
    2. Disconnect the battery’s negative terminal before beginning the project.
    3. The belt may be located on the front or side of the engine bay, depending on the orientation of the engine.
    4. The belt is routed around and through several pulleys that control various vehicle functions. Your vehicle’s maintenance manual likely has a diagram, or you can find one online. This will be important, both for removing and replacing the belt.
  2. Remove the old belt

    1. You may need to locate and either loosen or remove the belt tensioner. This step will require the socket set to de-tension the belt. Your exact process to loosen the tensioner will depend on the type and location of the tensioner itself. Refer to your vehicle’s repair manual for more information on this step.
    2. Slip the belt off of the pulley closest to you and carefully work your way down to remove the belt from each pulley along the way. If the belt is shredded or damaged, be sure to get any debris left behind as well.
  3. Install the new belt

    1. Following your vehicle’s belt diagram, re-route the serpentine belt around the various pulleys in the exact order the old one came off. If your tensioner or other components are damaged, replace them before attempting to install the new belt.

The Glossary: Terms and Parts To Know

Welcome to Bible School!

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.

Tensioner

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.

The Questionnaire

Car Bibles has the answers to all of your burning questions.

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.

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 Markovich

Tony 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.