New Serpentine Belt Squeal on Startup: What to Do? (Explained)

A serpentine belt is one uninterrupted belt that drives several peripheral devices in an automobile engine. It includes vital parts such as the alternator, power steering pump, and water pump. In short, this belt plays a vital role in an engine’s performance. Thus, you may worry about it when it squeals during a startup. So, you may ask:

If my new serpentine belt squeal on startup, what should I do? If you hear your new serpentine belt squeal, the tensioner pulley that works it out is likely failing or broken. This pulley can break down over time. As a result, it allows the belt to slide a bit. In most cases, you’ll need to fix or replace the pulley to stop the squealing noise.

Since you have a new serpentine belt, the squealing noise isn’t likely from the belt itself. In most cases, the squealing sound comes from a worn-out belt. However, if you replaced it recently, then the problem would be with the tensioner pulley.

In this article, we’ll walk you through this matter and help you understand a bit more about this issue coming from your serpentine belt. This way, you’ll have a sense of what to do if it ever happens in your car.

Without further ado, let’s get into it!

New Serpentine Belt Squeal on Startup

Why Does My Brand New Serpentine Belt Squeal?

A brand new serpentine belt can still produce squealing noise, especially if the tensioner pulley is worn out. Thus, even though you have a new belt, you can’t guarantee that your car will stop squealing.

The squealing noise from the serpentine belt usually happens during startup and acceleration. The reason is that your engine places a significant load on your alternator during these moments. 

Such a large load can cause a worn-out belt and tensioner pulley to squeal. Thus, even if you already replaced your belt and had a new one, you can still have that squealing noise if the pulley is also worn out.

As previously stated, this sort of noise is generated by a relative slide between the belts and pulley and will generally grow in intensity as the rpm advances.

How Do I Stop My New Serpentine Belt From Squeaking?

In general, you’ll want to find out where that squeaking noise comes from before you do anything. In most cases, it will be on the belt itself and the pulley. The belt starts to slide and scream if it does not retain continuous adherence to the different pulleys. Also, humidity on the ribbed side of the belt is frequently the source of belt squeals.

Now, if your belt is a new replacement, then you’ll want to look at the pulley first. Here are some things you can do to stop your new serpentine belt from squeaking:

Do some thorough checking.

Lift the hood of your engine bay and start your car. Take your arms and clothing apart from the motor and its parts at all times. 

Using a light, search for a location where you could spray the belt with WD-40 so that the textured side is immediately coated before it passes through a pulley.

Find the sound and search for a link between the sound and belt movement. This way, you can locate the exact location where the squealing originates.

Lubricate the belt.

Wear your protective goggles and avoid standing directly in front of the belt, as the spray will tend to fly out in a path, staining your clothes. 

Spray an adequate amount of WD-40 to gently coat the region where the scream occurs on the belt. To avoid the belt being saturated, use short, quick blasts.

As you do so, keep in mind not to oversaturate the belt with this lubricant. Overdoing the spray will cause significant slippage and eradicate the belt. Also, since WD-40 is a water-displacing lube, it should dry out the belt ribs.  

The scream will usually stop once the moisture is removed. Let the motor idle for a few moments before applying rubber treatment, also known as belt dressing, to the belt as described earlier.

This method will clean the ribbed surface of the belt and eliminate any remaining impurities. Do not overwhelm the belt, as you would with WD-40. Run the engine for a few moments further to be sure the noise vanished utterly.

What to do if the squealing noise continues:

The serpentine belt is glazed if the scream does not cease or returns rapidly. Belt glazing happens after it has been sliding throughout the surface of one or more pulleys for an extended period, and it is generally visible as a reflecting shine on the textured sides.

Since it can no longer retain a hold on the pulleys, a glazed belt will scream and must be changed. Once you’ve established that the belt needs to be replaced, please take a note of the belt’s route before pulling it.

You may find a route chart near the engine or on the bottom of the hood over most cars. Check that each pulley is spinning before disconnecting the belt. A glazed belt is frequently the consequence of a stuck pulley, and it is typically an indication of a more significant issue.

New Serpentine Belt Squeals When Accelerating: What to Do?

As I mentioned earlier, even a new serpentine belt can squeal when you accelerate, and it’s because the pulley where it runs is worn out. 

Like in an engine startup, the new serpentine belt squeals when accelerating because the engine places a large load in the alternator, and this part runs through the belt.

A serpentine belt runs the air conditioning, cooling system, alternator, and power steering pump. Since acceleration puts a lot of load in the alternator, it can cause excessive work for the belt to squeal.

A belt tensioner helps maintain the belt tight and is easy to remove and replace because it is such a big belt. However, if the belt is worn, it might slip and scream when the vehicle accelerates. Additionally, if any of the alternator’s pulleys are worn or loose, the belt might scream.

The most common causes of squealing come from a worn-out serpentine belt. Thus, if you have a new one, then the problem is likely from the pulley.

What you can do is lube your belt a little with WD-40, which will also help displace any water or moisture in it.


In a nutshell, a new serpentine belt can still squeal even if it’s a new replacement. Since the serpentine belt takes a lot of work, it can squeal, especially in critical moments such as startup and acceleration.

The best thing to do about this is to check where the squealing noise originates and see if your pulley also needs replacement. If not, you can spray some water-displacing lube such as WD-40 to remove the noise. One thing to note is to avoid overdoing the lubrication as it may also damage the belt.

Also Read:


Image credits – Canva

Share on:

My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more