How to Stop Your Serpentine Belt From Squeaking: Causes & Fixes

Any unusual noise from your car engine often means that something is wrong. Have you recently heard an uncomfortable squeaking sound from your car’s serpentine belt and were wondering how to stop it?

In this article, I’ll address what causes the serpentine belt to squeak. Additionally, read on to learn how to fix a squeaky belt and whether or not you can spray a WD-40 on a serpentine belt.

What Causes a Serpentine Belt to Squeak?

A serpentine belt is a vital engine accessory that performs various functions. Most modern cars only have one belt (serpentine), unlike traditional models with several belts carrying out different roles. For instance, it could have a fan belt or an accessory belt to power other engine components.

Your modern car can’t function without a serpentine belt as it conveys power to other engine components. If it malfunctions, your car’s AC compressor, the power steering pump, and the water pump will also not work. You’ll know that the serpentine belt isn’t okay if it produces a squeaking sound.

Some of the most common causes of a serpentine belt squeaking include weather conditions, wear and tear, improper belt installation, and misaligned pulley and tensioner.

Let’s take a closer look at these potential causes.

Weather Conditions

Unfavorable weather conditions could be the reason why your vehicle’s serpentine belt is squeaking. For instance, if it’s too cold, the belt will stiffen and make some noise after starting the engine. However, the noise will reduce or stop when the engine warms up.

Heavy fog and early morning dew also lead to squeaking as the moisture lands on the serpentine belt. The squeaks also reduce as the engine becomes warm.

Wear and Tear

The newest belts are more durable as they’re made from a long-lasting synthetic rubber called ethylene propylene diene terpolymer (EPDM). Even though modern serpentine belts last longer (after 100,000 miles) than traditional ones (50,000 miles), they eventually wear out.

A worn-out serpentine belt is one of the common reasons why it could be squeaking.

If the serpentine belt’s ribs or grooves are damaged, friction reduces, and a squeaking noise occurs. A worn-out belt may also overstretch, slip on a pulley, and produce a squeaking sound.

Improper Belt Installation

If you hear a squeak from your engine after a recent serpentine belt installation, it could be that you (or your mechanic) installed it wrongly. A wrong belt installation also means that it isn’t tensioned or re-tensioned properly. Hence, it can lead to further damages to the pumps, brackets, and motors.

Misaligned Pulley and Tensioner

The serpentine belt can start squeaking if it slips from the pulley due to misalignment. When this happens, it can either put more or less pressure on other engine accessories. Therefore, you could experience overheating, air conditioning, or power steering problems.

Defective Bearings

A squeak can also occur if the bearings are malfunctioning. To identify any defective bearing, open the hood and listen carefully to identify the source of the squeaking noise. If it only emanates from a single location, it’s most likely that a bearing is worn out.

You’ll identify a defective bearing if it appears glazed, doesn’t spin smoothly, or contains belt particles. You have to replace such defective bearings to stop the squeaking sound.

Grease or Oil Contamination

The serpentine belt can also produce a squeaking sound if lubricants from other engine components spill on it. You’ll most likely notice some oil or grease contamination on the backside of the belt. Such a situation isn’t good for the belt as it can lead to it malfunctioning and being damaged.

Hence, once you notice a shiny appearance on the serpentine belt, check if there are any coolant or lubricant leakages. Also, find out if there’s any pulley or tensioner misalignment.

How You Can Make a Serpentine Belt Stop Squeaking

Now that you know the possible causes of a serpentine belt squeaking, here’s how you can make it stop.

1. Diagnose the Root Cause of a Squeaking Serpentine Belt

The method you’ll use to quiet a squeaking serpentine belt will depend on its main cause. An occasional squeal could be due to some weather conditions or a loose serpentine belt. Continuous noises could result from misalignment of the belt and other engine accessories or worn-out components.

Hence, here’s how to diagnose the cause of a squeaking serpentine belt:

Switch Off the Engine and Open the Hood

To inspect the serpentine belt for wear and tear, use a flashlight and check if it has any damaged parts, including cracked or thinner regions. Also, check if the ribbed (back) section has any missing rubber. Lastly, look out for any shiny or glazed areas as lubricants or coolants could spill on the belt.

You can also use water to check if there are any damages to the belt. So, turn on the engine and spray some water on the ribbed section. If the noise fades, your belt may not be worn out. However, if it persists, it’s damaged, and you have to replace it.

Inspect the Tensioner

A loose belt will most probably produce a squeak. So, check its tension by pushing it inward for more than half an inch. If it can bend that far, the serpentine belt’s tensioner needs some re-tensioning.

Some tensioners are manually adjusted, while others require hydraulic force or spring loads. Hence, check your manufacturer’s manual to determine the best way to tighten the tensioner.

Check the Pulleys

If the belt isn’t the cause of the squeaking, the problem could be the pulleys or bearings. So, inspect the pulleys keenly for any misalignment or defective bearings. Misaligned pulley grooves will cause the belt to slip off.

The bearings could be worn out if you remove the belt and the pulleys don’t spin smoothly. Hence, you have to replace them.

2. Use Bar Soap as a Short-Term Solution

After diagnosing the cause of the squeaking sound from your engine, you should determine the best way to fix the problem.

Using soap is one of the fastest and easiest ways of quieting a squeaky serpentine belt. However, it’s a short-term solution, and you can only do it during an emergency or when you can’t get hold of a mechanic.

Also, note that using soap can either stop the squeaking noise or increase it in some cases.

How to Fix a Squeaky Belt With Soap

Here’s how to use soap to fix a squeaking serpentine belt:

  • Apply a bar soap on the ribbed side of the serpentine belt. If the noise doesn’t stop, it could be that the pulley is dirty. So, identify the cause of the dirt and clean the pulley using an appropriate solvent.
  • You can also use soapy water to reduce belt squeaking. Spray the soapy water on the serpentine belt and then wait to hear if the squeaking sound will reduce or stop. If it doesn’t, you should resort to other long-term solutions.

3. Replace the Belt

A worn-out serpentine belt will do your car no good. Even though it may still look okay, if a belt is beyond repair, the squeaking noise from your engine won’t stop. Hence, replacing it with a new one is the only remedy in such a situation.

When shopping for a new serpentine belt, ensure that it’s the appropriate size and suits your car’s model. Moreover, it’s advisable to buy an EPDM belt as it’s more durable. If you’re fixing the belt yourself, you’ll need a half-inch ratchet to loosen the tensioner pulley.

The cost of a new serpentine belt will depend on your car’s model. In most cases, the belt prices will be between $30 and $75. Some vehicle models will require you to also replace the tensioner when you install a new belt. A tensioner will cost around $40 to $70.

4. Tighten the Belt

At times, the squeaking noise from your engine could result from a loose serpentine belt. So, to determine if this is the cause of the problem, open the car hood and check if the belt is loose. Moreover, you should also check if the belt is misaligned on the pulleys and align it properly.

A loose or misaligned belt will lead to wear and tear. Eventually, other engine accessories will also malfunction. Therefore, tightening and aligning the belt properly are long-term solutions to squeaking.

5. Apply Belt Dressing (Squeal Spray)

Applying a squeal spray is another temporal method of quieting a squeaking car. Squeal sprays (belt dressings) are aerosols and conditioners that improve friction between a serpentine belt and the pulleys. Therefore, they help to minimize or stop engine squeaks.

To apply a belt dressing:

  1. Open the car hood and direct the squeal spray towards the belt. Note that your engine should be running but with the brakes on.
  2. Spray the dressing on the belt to fix the squeaking problem. However, take precautions as belt dressings are flammable and can also cause skin irritations. Therefore, it’s advisable to have a pair of gloves and safety goggles when you handle such chemicals.

Squeal sprays are also not appropriate for EPDM serpentine belts.

As I mentioned earlier, a belt dressing is a short-term fix, and it may only hide the underlying problem for some time. Moreover, the sprays can also adversely affect the serpentine belt as they contain lubricants and sticky components.

6. Repair or Replace Defective Bearings

If you noticed that a defective bearing was the cause of the squeaking sound on your engine, you have to determine whether to repair or replace it. A malfunctioning bearing will exhibit problems on the serpentine belt or pulleys. Hence, you might observe some vibrations or wobbling pulleys.

Well, you can fix the bearings through greasing or repairing them yourself (not advisable for newbies). If the problem persists, have a mechanic sort out the problem.

Repairing and replacing defective bearings are long-term solutions to squeaking serpentine belts. However, you must carry out the procedures correctly to achieve this.

7. Repair or Replace Leaking Accessories

Leaking engine components usually spill coolants, oil, or grease on the serpentine belt. Such contamination will eventually damage the belt. Hence, it’s advisable to fix the leakage as soon as you identify it. But it’s advisable to have your car checked by a professional mechanic who will diagnose the root cause of the leakage and determine a long-term solution.

Can You Spray WD40 on a Serpentine Belt?

You might have heard that WD-40 is an effective way to quiet a squeaking serpentine belt. However, how true is this assumption?

WD-40 (Water Displacement 40th formula) is a versatile product that prevents rusting, lubricates, and displaces moisture. The aerosol was initially meant for aerospace use by Convair to protect the outer layer of the Atlas missile from rust. However, its effectiveness triggered people to use it at home.

Since WD-40 displaces moisture from metal, people have also been using it to relieve the squeaking noise from serpentine belts. However, the belt largely constitutes rubber components. Hence, spraying WD-40 on the belt will eventually damage these parts.

So, you can spray WD-40 on a serpentine belt to reduce the squeaking noise. However, it’s only a short-term fix and continued use of this product can damage other engine accessories, including the bearings.


Your car’s serpentine belt could be squeaking due to several reasons. The first step to fixing this problem is to determine the root cause of the noise. It could be that the belt or other engine components are misaligned or damaged. So, after identifying the issue, fix it immediately to prevent further malfunctioning.

However, avoid short-term solutions as they’ll cost you more money in the future. It’s always recommended to consult a professional mechanic when the problem is beyond your wits.

Related: Why Is My Alternator Making Noise and How Do I Fix It?

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