Squeaky Serpentine Belt – Explanation, Causes & How to Fix it

Squeaky Serpentine Belt – Explanation, Causes & How to Fix it

Let’s imagine a scenario. You and your friends have been planning for a travel vacation for months now, and the day is finally here! You have packed your bags, and you are ready to go.

And now you notice slight squeaks coming from the car, particularly its bonnet, but you ignore it. You have been planning this trip for a long time, and you are not going to let some weird noises delay it. Your car will be checked when you come back home – nothing to worry about.

You and your friends finally drive onto the highway when your car jerks, and you have to pull it to the side. The vehicle does not start again.

Should’ve checked the source of the noise, right?

These squeals that come from the bonnet of your car are usually from a faulty serpentine belt.

A serpentine belt is one of the most integral parts of any automobile. While you might not notice, it will only come to light when something goes wrong with the air-conditioner, the water pump, the power steering or the alternator of your car.

Before we get into why a serpentine belt screeches, we will talk about the basics.

What is a Serpentine Belt?

Simply put, a Serpentine belt is a single long belt that holds many vital components together and makes sure that they keep functioning. It is effective and convenient compared to the primitive multiple belt system in most automobiles. It is easy to maintain as well as replace.

Why does a serpentine belt squeak

A serpentine belt is put under increased tension without overcoming its elasticity limit, which reduces slip. This increases its mechanical efficiency as well as its lifespan.

Moreover, it also reduces the excessive load of the engine and increases the amount of power it provides. The increased tension also minimizes the change of the v-belts to rotate in the groove.

Without a serpentine belt, the electrical components of your automobile, like the lights and the horn, would stop operating. The battery will not get charged, which will ultimately shut down your car, and it can also stop the cooling or heating system. It attaches all these components to the part of the engine that makes them functional.

Why does a serpentine belt squeak?

A Serpentine belt can become noisy for many reasons. It can be adverse weather conditions, delayed maintenance, the issue with the internal bearings, and leaking fluids.

The sounds usually come when your serpentine belt has become adorned with scratches or tears. Moreover, over time, the belt loses its elasticity and becomes loose. So a loose serpentine belt can create noise too.

The range of this noise can vary from a low, not so noticeable buzz to a loud and annoying squeal that would not let you attend a call or listen to the radio in your car.

Different Causes of A Squeaky Serpentine Belt:

Below we will discuss different circumstances due to which your serpentine belt can become squeaky.


One of the most common causes of the squeak of the belt is decreased friction of the belt. When the engine turns on, it starts and turns the pulleys, which further drive the belt.

If you have not changed your belt for a long time, the belt, due to recurring function, can lose its grip on one of the pulleys, which it spins. The surface of the belt in contact has lost its roughness and might have become smooth and worn. This will lower its friction. Furthermore, it makes the belt slip.

One of the major indications of a slipped belt is a loud squeal. A squeal that will be like the squeal produced by someone who drags their nails on a blackboard.


If you live in an acquainted area with frequent rain or snowfall, your engine might be squeaking because of the water that seeped into the bonnet.

When your car passes through a water body, like a puddle, it might cause the surface of the belt to lose its bumpiness and ruggedness, which will make it slip. The morning moisture can also cause your belt to slip.

The belt becomes too smooth to hold onto the pulleys that drive the engine properly. This will cause your belt to slip from its lace and slow down the operation of your car.

Improper Tension of the Belt:

Another cause of a squeaky serpentine belt can be its tension. The tension of a belt is how tightly it winds around the alternator, water pump, and various other components that drive the engine.

Most belts have an automatic belt tensioner, which is simply a spring-loaded arm that has an idler pulley attached to it. The tension in the spring will turn the pulleys, which push on the belt to keep its ideal tension.

If the tensioner is worn out, it will result in a squeaky operation of the serpentine belt. If your vehicle is not equipped with an automatic tensioner, the tension is adjusted by fixing the idler pulley or one of its accessories.

The opposite can be dangerous too. If the tension is higher than required, your belt might snap into two pieces and stop the car from functioning. A serpentine belt helps to deliver power to the engine so that your engine keeps on charging.

If the belt snaps, the engine will not get charged, and this will turn off your car. Moreover, other functions of the vehicle would stop operating as well.

Loose nuts and bolts:

Loose nuts and bolts can reduce the friction as well as the tension of the belt. This will not only cause your car to let out a variety of screeches, but also affect the functionality of different electrical accessories residing in your car.

We use nuts and bolts to hold the pulley, spring-loaded arm, or its accessories in place. Also, we use them to adjust these components until the desired tension is maintained. Thus, the sounds coming from your engine might be because of these nuts and bolts.

Damaged Accessories:

What if your belt is squeaking even though it has the ideal tension, and it is dry? What can be the cause of the noise then?

Sometimes, the pulleys, alternator, or steering pump attached to the belt might put extra strain on the belt. This occurs when you have a bent or damaged accessory. It will make the belt exert extra power to drive these components.

The pulleys or their bearings in newer models of automobiles are made from plastic, which is not durable. Any damage to the pulley will damage the efficiency of the belt.

Lack of Maintenance:

Oil, grease, and dirt. These three contaminants deter any electronic or mechanical equipment. Your serpentine belt is also susceptible to these agents.

Thus, if you have not taken your car to a maintenance shop in a while now, you should take it to one ASAP. If you find it hard to turn the steering wheel, it might be due to the oil, dirt, and grease that have attacked your belt.

One of the causes of the noise coming from your bonnet can be the accumulation of these detriments on the belt surface.

Not only will they reduce the friction of your belt, but they will also wear it out and even cause it to tear.

How to Examine a Serpentine Belt:

Before we talk about the different ways of how to fix the problems listed above, we need to know how to inspect a serpentine belt ourselves to see if it is functional or not.

We recommend you check your serpentine belt at least once a month. Whenever you take your car to a maintenance station for service or to get its oil changed, get the serpentine belt checked too.

If a serpentine belt appears to be overly rugged or has visible cracks over its surface, you need to get it immediately replaced.

Minute cracks along the ribbed side of the serpentine belt are normal, but if the cracks are significant or the serpentine belt has a few rubber pieces missing from it, the belt has reached the end of its life.

Professionals have shared with us a simple thumb rule to check out the durability of a neoprene belt. If the cracks are visible and are approximately 3 millimeters apart, you need to get the belt changed straight away! Cracks in the rubber of the belt are a major indication that it will fail to operate soon. So better be safe than sorry and replace it.

Small, minute cracks that appear at a greater distance from each other on the serpentine belt are normal. So, if the scratches are minor, you do not have to change the belt.

Late models of automobiles typically have serpentine belts made from EDPM rubber, which is a type of synthetic rubber.  It is rarely susceptible to cracks for a longer time as compared to the neoprene belts.

But this does not mean that you do not have to check the condition of the belt periodically! In these belts, usually, the V-grooves that are on the underside of the belt might be worn out. This will cause the belt to slip.

Thus, whether you have a neoprene belt or an EDPM belt, it is essential to check it yourself or a mechanic after every few weeks.

How to Fix a Squeaky Serpentine Belt:

Different Causes of A Squeaky Serpentine Belt


The most common and applicable solution for a noisy serpentine belt is a replacement. Since we know that a squeaky serpentine belt is usually the cause of different issues, the most prevalent one is a worn belt.

Thus, if the belt residing in your engine has visible scratches or has chunks of it missing, the best option is to replace it. This will restore the high-end operation of each electronic unit that is run with the help of the serpentine belt.

While looking for a new serpentine belt, make sure you buy one that is durable. There are two major types of belts available in the market these days; a Neoprene Serpentine belt and an EDPM one.

As we have discussed above, EPDM is better for high mileage and will last much longer than a neoprene one.

You should carefully examine the belt you have chosen and notice its length, reliability, and friction to buy one that seems befitting for your automobile. Preferably, you should consult a professional before buying a belt.

Belt Dressing Conditioner/ Lubricant:

A Belt Dressing Lubricant will keep your belt as moist as it needs to be to work optimally.  A Belt conditioner or a spray will soften the rubber of the belt. This will keep it dry and would not let it slip from its place. In addition to stopping the squeals let out by your car, it will also ensure a longer belt lifespan.

According to several technicians and mechanics, you should apply the lubricant to the V-groove of the belt after driving for 3000 miles each time or when you change the oil.

Belt Dressing Conditioner is a tool that will help you maintain the condition of your belt. While it might not fix all sorts of squeaks, but if your belt keeps slipping because of the dried out rubber, this product will keep it soft and moisturized.

Take the belt out of the engine and spray the lubricant on both sides. Wait for it to dry out before respraying the dressing. Once this coating gets absorbed, place the serpentine belt back into its designated place.

When you start your car, the squeaks might be loud, but that is because of the lubricant’s excessive moisture. After a while, the water will dry out, and your car will drive smoothly without any squeak!

Belt Tension Measuring Tool:

A belt tension measuring tool will help you estimate the proper tension that your belt requires to pull the pulleys and drive the alternator, air-conditioner, etc. It is not only accurate, but it is easy to use by anyone and gives you readings within seconds. It is a small portable device that comes with a measuring probe and a cable to help you access areas that are difficult to reach.

This electric appliance is equipped with a microprocessor that measures the tension of the belts precisely and also controls the force f the belt drives. It detects belt frequencies and gives you a value in hertz, pound, or Newton force.

This value is measured with the required tension, which is typically mentioned in the owner’s manual. According to the requirement, you can quickly increase or decrease the tension so that your belt works perfectly.

All you need to do is turn off the engine so you can measure it accurately. It is a helpful device that can help you avoid potential hazards.

Realign The Belt And The Pulleys:

A misaligned belt or pulley is one of the leading causes of a noisy serpentine belt. Thus, open the hood of your car and examine the pulleys and the belt to see if they have slipped from their original place.

To check the alignment of your belt, use a measuring tape or a scale. The belt should touch the outer two edges of the pulleys. If it is not straight, there will be a gap between the belt and the pulley’s outer edges.

Thus, if it is misaligned, you need to take it to any car service shop to get it aligned ideally.

Shine A Flashlight On The Belt:

A simple and easy way to detect any cracks or scratches on your serpentine belt is to shine a flashlight on it. Every kind of damage will be visible to you, and this will help you determine whether it is time to change the belt or not.

The light will also help you examine the condition of the belt. You would be able to see whether it is dried out and needs a lubricant or whether it is glazed over.

Thus, if it is glazed over or has large cracks, it is time to replace the belt. If it dries out, you can spray the conditioner over it.

Pour Water:

Start the engine of your car and then pour a glass on the water on the place where the voice is coming from. As we have discussed before, excessive moisture will cause a serpentine belt to let out excessive noise.

So, when you pour water on the belt, you will recognize the precise location of the sound better. The squeals can be coming from the pulley too. Thus, this simple test will let you better examine the source of the noise.

Things to Keep In Mind While Checking the Serpentine Belt:

Things to Keep In Mind While Checking the Serpentine Belt

Although it is straightforward to detect, examine, and fix a faulty serpentine belt, you should take some extra safety. These measures will ensure your safety and reduce the possibility of any possible life-threatening situation from occurring.

Pull your hair up!

While examining the engine when it is ON, you must tie your hair up in a bun or a pony. You should also roll up the sleeves of your shirt so that neither your hair nor your clothes tangles into the belt.

This is extremely hazardous and can cause serious injuries.

Turn of the Engine:

Before using a tension measuring device or WD-40 to clean the belt, turn off the engine! It is unsafe to use the device while the engine is on since it will not be able to measure the tension correctly.

Furthermore, it is wise to take out the serpentine belt to clean it. SO, turn the engine off, let it cool down and then take the serpentine belt out to clean it.

Let the Engine Cool Down:

Do not examine the components on the engine while the engine is still hot. This can burn your fingers and cause injuries.

Furthermore, do not pour water on the engine while it is still warm. This may damage it. If you are testing to pinpoint the source of noise, pour the water on a functioning engine very slowly.


The serpentine belt is one of the most important components of your engine. Without it, the engine of your car will not function properly. Thus, it is vital to check it out after every few weeks to ensure that it works smoothly.

You should never skip your car’s monthly maintenance because it will help you detect various defects of your vehicle or help you avoid defects effectively. You can check out the components yourself, or you can take it to a technician.

Moreover, you should take your car once every few months to a mechanic so that he or she can examine every part of your car to detect any errors.

Furthermore, it would help if you got your car a checkup the moment it starts producing any sorts of noise. As we have discussed above, a faulty serpentine belt can hinder multiple functions of the car, including the engine’s ability to charge effectively.

You should always consult an expert or read the user manual to take care of the serpentine belt correctly. This will reduce as many chances as possible for the belt to function properly.