What is a Serpentine Belt & When Should You Replace It

A bad or faulty alternator is something that almost every motorist has to deal with at some point as they drive. An Alternator is the vehicle’s component that maintains the battery’s charge in order to help the battery supply electrical power to other electronic components of the car.

A car without an alternator would have trouble supplying power that allows all its electronic components to function even for a short period.

This means that These electronic components in the vehicle will not work properly since they will not have enough power generated by the vehicle to enable them to function properly.

By keeping the battery charged, the alternator allows the power produced by the battery to flow through the vehicle regularly.

Serpentine Belts are rubber belts that help deliver power to the engine’s accessories, including the alternator and power steering pump, the air conditioner compressor, and sometimes even the water pump.

An alternator could not perform all its functions properly without the Serpentine Belt (also known as the alternator belt).

As we proceed through this article, we will explain what a Serpentine Belt is, what it does, and how you can replace your Serpentine Belt if it gets damaged. 

Ready? Let’s get started!

What is a Serpentine Belt?

Serpentine Belts are rubber belts that help deliver power to the engine’s accessories, including the alternator and power steering pump, the air conditioner compressor, and sometimes even the water pump.

A serpentine belt can also be known as an alternator belt, fan belt, or accessory belt, which is why some of these terms will be used interchangeably in this guide. 

Before now, cars had several drive belts joining the engine to various accessories in a vehicle such as cooling fans and other parts.

Nowadays, modern automobiles use only a single belt connected through various pulleys to properly and efficiently power everything else on the vehicle.

The only drawback of utilizing only one belt is that if the Serpentine Belt in your vehicle malfunctions, you’ll lose power in all the vehicle components! For instance, You will be unable to operate the AC and steering of your vehicle.

In the long run, this can cause your engine to get overheated, and your battery could also fail. Furthermore, it would also damage the components of the engine that the battery is in charge of regulating.

Checking your serpentine belt at regular time intervals is crucial for this reason.

What Does The Serpentine Belt Do?

The serpentine belt must be in good operating condition for your car’s engine and systems to function properly.

A car’s alternator, power steering pump, air conditioning compressor, and possibly the vehicle’s water pump are all powered with the help of the serpentine belt.

The serpentine belt constantly rotates when the car is running. As the car runs through its belt, its rotational power is transferred to other parts to run different accessories on the car. This is done through a pulley system and a tensioner.

How To Tell If The Serpentine Belt is Bad 

Serpentine Belt
Credits: SOORACHET KHEAWHOM / Shutterstock

Serpentine belts are used nearly every day as you drive your car. There is the possibility that it may wear out or may come out of the pulley as it is used constantly, and different kinds of symptoms can occur as a result.

It is essential to replace the Serpentine immediately if any of these symptoms appear. By not changing the serpentine belt, it is possible you may be stranded at an unfamiliar location if your car loses power due to a bad serpentine belt.

Here are the five symptoms of a Bad Serpentine or alternator belt.

1. Battery Warning Light

Your battery warning light will also come on as a sign that you need to inspect your batter or serpentine belt and replace it if the need arises. However, this light does not always mean you have a problem with your vehicle’s battery.

Maybe there is a problem with the electrical system in the vehicle, which you need to check out that is probably causing problems for the car battery.

You should take your vehicle to your local mechanic immediately to find out what the problem is or, if you are sure, simply try to solve the problem at home.

2. Vehicle Stalls

Your engine can quit if the Serpentine belt becomes too loose while driving your vehicle, and this can force you to pull over by the roadside to properly access your car.

Obviously, you don’t want this to happen on a highway or when traffic is heavy along the highway as your car stopping as a result of loss of power can affect you and other motorists using the road.

However before your car goes out, you might notice some flickering lights in your vehicle, and a loose alternator belt could cause the flickering of the lights if this is the case.

3. Flickering/Dimming Lights. 

In the event that your car’s headlights flicker, or dim, or the interior lights dim while you’re driving, it could indicate a problem with your car’s battery or the alternator.

As the power is not getting to the lights when there is a Serpentine belt issue, lights may dim or flicker for quite a while before they go out completely. It could also be a sign that the alternator is approaching failure.

However, this is dependent on the age of the alternator and how long you have been using it.

4. Dead Battery

The battery attempts to serve as the automobile’s sole power source if the alternator cannot fully charge it because of a faulty alternator belt.

Due to the inability of the car’s battery to meet all the electricity demands and act as the vehicle’s power source alone, the battery will most likely deplete in a short period.

5. Chirping or Squealing Noise

An engine can make various noises if the Serpentine belt is worn out or loose. The serpentine belt may make various sounds when it rotates if it is not tight enough or is improperly positioned on the pulleys.

Cars are often heard making this sound, which is more common during cold weather. The issue will become more serious if you don’t replace the serpentine belt/alternator belt and may cause the belt to break off or, in some cases, fall off a pulley if not replaced.

How Long Does a Serpentine belt Last

Maintaining your Serpentine belt properly will ensure that it will last between 3 and 4 years. If you use reasonable mileage as an average, the clock is expected to stay with your alternator for anywhere from 6oK to 100K miles.

This is impressive. Nevertheless, some belts may need to be manually tightened by the driver and might need adjustment before wearing or after being used for a longer time. 

Some belts have self-tensioning mechanisms that can wear out over time and might require maintenance. 

When either of these conditions occurs, the belt will fail to function properly and result in the car decelerating with constant knocking sounds coming from the engine compartment.

How Much Does It Cost To Replace a Serpentine Belt

The cost of replacing a Serpentine belt is typically between $100 and $200. The part cost can range from $20 to $50, and the labor costs are between $75 to $120.

The actual cost of replacing the part will depend on the time it will take for the mechanic to reach the Serpentine belt.

In some cases, a belt may be hard to reach due to the engine’s design. This could make it harder to repair, meaning that more labor is required. 

However, if the belt is easy to access, this indicates that labor should only take one hour in total. The labor charges won’t exceed $300 for an alternator belt replacement in many cases

Can You Drive With a Failing Serpentine Belt?

Yes, your car can run with a broken serpentine belt. The starter motor and ignition system work together to make the car’s engine run. But if you want your car running for long periods of time, you’ll need to replace that broken serpentine belt.

The serpentine belt is a drive belt that runs your car’s accessories, like the alternator, power steering pump, air conditioning compressor and water pump. If the belt snaps or breaks, these essential components can no longer work properly.

If you run your car with a broken serpentine belt, the car will eventually stall. That’s because the alternator can no longer produce enough power to keep your battery charged. Without a fully-charged battery, your car won’t start again until you fix the problem.

Also Read: How Much Really Does An Alternator Cost?

How to Replace A Serpentine belt

How to Replace A Serpentine belt
Credits: J.J. Gouin / Shutterstock

If you want to replace your Serpentine belt yourself, follow these steps.

1. Check the Serpentine belt

One of the most common problems with serpentine belts, also called “alternator belts,” is that they jump off of the alternator pulley as they get loose. 

This is often caused by the constant usage of the serpentine belt. One of the best ways to test a belt before carefully removing it is to see if it’s too loose or too tight. 

(if you can move it enough to move your hand between its teeth or if it displaces above ½ inch or ½ inch). Try lifting up on one end of the belt – if it lifts off now, you know that the serpentine belt should be replaced.

2. Release the Tension

Releasing the tension on the Serpentine belt will enable you to pull it out. To begin, you must find the pulley that is used to tension the belt. 

In order to remove the serpentine belt on your car, it may be helpful to first identify the pulley that is used to tighten the belt. Tension must be loosened before removing the serpentine belt.

There are two ways that tensioner pulleys can be connected: either by bolting on the backside of the pulley or by bolting directly onto the engine block. To remove it, first, find a ratchet or wrench that fits into the bolt hole, and then simply turn it counterclockwise to loosen it.

3. Get familiar With the Serpentine Belt.

The serpentine belt takes a winding path of twists and turns throughout the engine. Before removing the old belt and prior to installing the new belt, make sure you know its path from beginning to end.

You’ll want to keep track of every step it takes so that you can replace the belt on the exact same path.

The instructions on how to use the belt must be consulted in order to be able to replace it correctly. You could make your own instructions by making drawings or by taking photographs of how the serpentine belt is placed before even removing it.

4. Install the New Serpentine Belt

Place a new belt on each pulley apart from the alternator, making sure to put the right side of the belt against the right part of the pulley.

You can consult the previously provided drawing or photo for any relevant details about how the belt connects in these places. To avoid damaging your car, ensure that the serpentine belt is properly installed in your vehicle.

Using your wrench, open the alternator tensioner by turning it in the direction that loosens it. Then, put the drive belt over the pulley and keep turning to loosen more. Do not allow either yourself or anyone else nearby to get hurt or injured while working on your vehicle.

Once you’ve turned a bit more, use your wrench once again to unlock the alternator tensioner.

5. Make the Final Check

Examine the serpentine belt and ensure its tension is correct by pressing against it. Depending on your vehicle’s make and model, it should not move by more than 1/4 or 1/2.

You are now ready to go. Be sure to take all instruments and rags out of the engine compartment. Now you can connect your negative cable to the battery to begin your vehicle.

Congratulations! You did it! Once you’ve removed all of the equipment and tools you used in working from your engine compartment, you can now be able to start up your vehicle and test it.

Also, Check Out this Video Guide on How to replace Your cars Serpentine Belt

Frequently Asked Questions

What is a Serpentine Belt?

The serpentine belt is the key component responsible for delivering power to your car’s engine components. This includes powering accessories and components such as your alternator, power steering pump, air conditioning compressor, and sometimes even your water pump.

Can you drive with a broken alternator belt?

This is indeed correct. Your car can very well start if your alternator belt is either damaged or absent as long as you have a fully functioning battery. For the engine to be started and to bring about the combustion process, some power must be generated by the starter motor.
One of the starter motor’s tasks is sending electricity to the ignition system, and this task will start your vehicle’s engine running.

What causes a Serpentine belt to break?

Issues with serpentine belts are often related to problems in the pulley or bearing. Bad pulleys and failing bearings may cause serpentine belt breaks and other issues that can lead to other problems too.

What happens when the Serpentine belt goes bad?

The serpentine belt is one of the most important components in a vehicle because it helps power all of the vehicle’s systems, including your AC and radio. If this belt goes bad, dirty, damaged, or fails, your car won’t be able to run right.

How much does it cost to replace a serpentine belt?

Serpentine belt replacement costs can range between $100 to $200. The component price ranges from $25 to $80, while the labor price is between $75 to $120. The actual cost of replacing the part will be based on the time it takes for the technician to reach the belt of your alternator.

How long should a Serpentine belt last?

Maintaining your Serpentine belt properly will ensure that it will last somewhere between 3 and 4 years. If you use reasonable mileage as an average, the clock is expected to stay with your alternator for anywhere from 6oK to 100K miles.

When should I replace the Serpentine belt?

In general, belts last 3–4 years. Ask your mechanic to inspect the belt every time you change your oil. Cracks, fraying, or looseness is a sign that the belt requires replacement.

What does a broken alternator belt sound like?

A damaged alternator belt can make loud, striking, or slapping noises that come from the underbelly of your car’s hood. Another sign of a broken alternator belt is that The battery-shaped warning light may also illuminate because the alternator cannot recharge your battery.

How tight does an alternator belt need to be?

As a general rule, make sure the belt driving the alternator is not more than 1/2 inch from its middle whenever it twists away. If the belt is twisted more than that, the belt is too loose; if it doesn’t twist as much as it should, then the belt is too tight – and won’t be suitable for your vehicle.


The serpentine belt is the key component that is responsible for delivering power to your car’s engine components. This includes powering accessories and components such as your alternator, power steering pump, air conditioning compressor, and sometimes even your water pump.

If you notice any signs of a bad serpentine belt we have discussed, be sure to take your vehicle to get fully inspected by an auto technician and get it fixed immediately.

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