Car Squealing When Accelerating [Solved]

Cars make all kinds of noises. Not all of them are signs of trouble, but in some cases, noise is your car’s way of trying to tell you there is something wrong.

Quick Answer

If your car is squealing when you accelerate it could be due to something minor, such as an issue with your car’s belts or just a little cold weather, to something more severe, such as an issue with your pulleys or alternator. It is best to take your car into the shop and have a professional mechanic examine it.

If you have some knowledge though, you might be able to diagnose the issue yourself, particularly if it’s one of the minor ones.

Car Squealing When Accelerating – What Could It Mean?

There are surprisingly fewer causes for squealing when accelerating than one might expect, making the diagnostic process a bit easier.

Causes for Squealing When Accelerating

For the most part, squealing when accelerating can be attributed to an issue with your car’s belts. Problems with your car’s belts are relatively quick and inexpensive to solve. However, there are a couple of other possibilities to consider.

Loose or worn belt: The most likely problem is a loose or worn belt, the most common of which is your vehicle’s serpentine belt. Over time, belts may become worn and stretch. When you accelerate, the belt cannot easily accommodate the change in speed, causing it to slip and squeak.

Serpentine belts are decently easy to replace and relatively cheap as far as car issues come. If your vehicle happens to have them, the issue may also be V-belts; these belts work together to do the same job a serpentine does. Replacing a v-belt will also be cheap but tends to be a little more tedious to replace and diagnose, as there are multiple attached to your engine, and getting to one might mean going through others.

Cold weather: This is another common cause of car squealing in general. In extremely cold weather, there’s a good chance your belt(s) will become brittle due to it being rubber. Thus, it will be less pliable and cause a squealing noise on acceleration, as it won’t move as easily in conjunction with the pulleys.

Just wait for your car to warm up and the squealing should go away, assuming the cold was the issue. Note, this may be an early sign of your belt(s) beginning to wear or loosen.

Excessive belt tension: As you know now, belt tension is one of the major causes of squealing while accelerating, as the belts must work in time with your pulleys. This tension is controlled by a belt tensioner. If that tensioner is applying too much tension it makes the belt less pliable, just like cold weather, resulting in the squealing noise.

Simply have the tension adjusted and the belt checked for any related wear and the squealing should stop.

Loose or worn pulleys: Pulleys typically have bearings in them that allow for them to turn. Over time, the bearings begin to wear and fail, and thus squeal. The idler pulley is the most known for this happening. Some pulleys are attached to shafts that have independent bearings that are also subject to fail, such as the power steering pump, air conditioner compressor, alternator, and water pump. If a pulley seizes up, from failed bearings or otherwise, the belt attached to it will begin to squeal, since it will be riding on a stationary pulley.

This is typically an expensive and involved issue, requiring a mechanic.

An old or failing belt tensioner: Belt tensioners have a pivot on them that may go bad over time, causing the belt to not ride completely on the pulleys. The spring in the tensioner can also go bad, which will loosen the pressure on the belt. In either case, the attached belt won’t have enough traction, resulting in slippage that makes a squealing sound.

If you have the right tools and feel confident in your ability, like with belts the tensioner is an easy job to replace and will also cost around the same.

An old or failing alternator: Just like with pulleys, a vehicle’s alternator has bearings that wear over time. When they are deformed or smoothed down, it causes a change in tension and thus a squealing noise.

This is a fairly complex and expensive fix and will definitely require a mechanic. In some instances, they may even decide it’s more beneficial (due to labor costs and other potential damage) to replace the whole system.

Serpentine Belts, V-Belts, and Synchronous Belts – What do they do?

Saying that there is a belt issue is rather non-descript, as there are a couple of options that could be causing the squealing sound, and one that will probably not.

Serpentine Belt

The serpentine belt is a single, continuous belt that connects to and powers the engine’s peripheral devices, such as the air pump, water pump, power steering pump, alternator, and air conditioning compressor. Typically, it is attached to the idler pulleys and/or a belt tensioner that assist in its job. It gets its name from the serpentine shape it takes in order to pass over multiple pulleys to avoid slipping.

Since the serpentine belt drives multiple functions of the vehicle, if it breaks or is knocked loose, those functions also go into decline or stop working entirely.


V-belts are in many older vehicles, but fewer and fewer new ones. They are replaced by the serpentine belt and covered the same function; driving and providing power to the engine’s peripheral devices. However, rather than one continuous belt doing the job, you would need multiple v-belts to power all the periphery functions. An example of a v-belt would be the fan belt, another common culprit to squealing when accelerating.

This is somewhat of a blessing and a curse, as when a belt begins to fail it can be harder to diagnose than a serpentine belt, as you would have to potentially check each one. Replacing them is also a bit more difficult, as more belts meant more layering.

Synchronous Belt

Also known as the timing belt, timing chain, or cambelt, the synchronous belt is a part of the internal combustion engine. Its job is to synchronize the rotation of the crankshaft and camshaft(s) to ensure the engine’s valves will open and close at the right time. This belt is typically not responsible for squeaking during accelerating. Instead, you would likely either be unable to start your engine, or blow up your engine, if the synchronous belt fails.

Is It Safe to Continue Driving?

In general, you shouldn’t continue driving your vehicle while you are hearing a squealing noise. If the noise is tied to acceleration, you might be able to get away with it so long as you are not pressing on the gas pedal too suddenly or quickly. But, you should only do so for short drives, such as driving to the mechanic, perhaps? The longer you wait, the more risk is involved. If you were to continue to drive long term with any of the aforementioned issues, you risk the following:

  • If you have a worn-down part already, continuing to drive will only worsen the damage and potentially cause harm to any of the connected systems
  • Since the serpentine belt controls a large portion of the periphery functions, if it breaks, is misaligned, or even just slips, it can result in a loss of function
  • Loss of vehicle function mid-drive could cause an accident, or even just add an expensive tow fee to the cost of already necessary repairs
  • A lack of pressure and tension in your serpentine belt could result in heavy steering, which poses a threat to safety
  • As long as your alternator can spin, it will continue to provide power; however, if it seizes up and/or the bearing fully fails, you also run the risk of losing power to your battery and vehicle, stopping at the wrong moment
  • Additionally, continuing to drive with a failing alternator can create an expensive issue, as you will do more damage over time and potentially risk other systems connected to it, such as your serpentine belt

Additional Signs of Issues with Serpentine Belt

A failing belt is hard to miss with the high-pitched squealing that typically accompanies it. In addition to the squealing, a lousy belt will cause a slew of other possible issues, sometimes even predating the squealing. These include:

Low battery light: Since the serpentine belt also provides power to the alternator, which in turn charges your vehicle’s battery, any failings the belt has extends to the battery as well. So, if your low battery light comes on or you find your battery struggling to maintain a charge, but it isn’t quite time for a replacement yet, it might be a sign of your serpentine struggling.

Trouble with interior lighting: On a similar note, the battery also powers your interior lighting. Flickering or dimming interior lights tend to signal an issue with your alternator or battery, which your serpentine belt happens to power. In some cases, failures of the belt will extend to failures in your lights.

Overheating: The serpentine belt can also power the water pump, which cools your engine. If your car is running hotter than normal, this can also signal a failing belt.

Difficulty steering: Typically, the serpentine belt also drives the power steering pump. If the squealing becomes louder when turning, this can also be a sign of a poor belt. In addition, you may begin to feel added tension when steering.

Issues with AC: Your serpentine belt is responsible for the AC system running smoothly. So, if you notice some squealing or chirping when the AC turns on, this might also be a serpentine issue, especially if the AC works in tandem with the acceleration to create a more pronounced squeal.

Other types of Squealing Noises – Know the difference

Not all squealing sounds are the same, and each one tends to occur at a different time or during a different action. For example, you may hear squealing when:

  • Braking – this tells you it is time to get your brake system checked, replace your pads, or check for an obstruction
  • When starting – this is likely also caused by a serpentine belt, as the engine starting will get the belts turning to power other systems
  • When steering – this could be a sign of a serpentine issue, but may also be related to a fault in the power steering system itself

Each one of these issues is cause for concern. The serpentine belt has already been discussed, but difficulty breaking or steering could be life-threatening, as both are extremely important functions.

Frequently Asked Questions Relating to Car Squealing When Accelerating

Asking questions about your vehicle’s health is important in your continued safety as a driver. Here are some common ones related to what has been discussed in this article about when your car squeals while accelerating.

How much does it cost to replace a belt? Luckily, a serpentine replacement is very inexpensive compared to many car repairs. The belt itself only costs around $25-$80 and is pretty easy to install for the average vehicle owner. If you aren’t confident enough in your own ability, or would rather have someone else do it, the labor costs would probably add an extra $75-120 to the cost of the part, for a total of $100-$200.

How long does a Serpentine belt last? Most serpentine belts will last for a while before you need to worry about replacing them. The lifespan of the belt depends largely on the material it is made of, i.e. the quality of the belt. Older style belts typically last around 50,000 miles before you start to see an issue. Those made from EPDM rubber, the newer style, can last up to 100,000 miles.

Wrap Up

Typically, you can attribute any squealing while accelerating, or even just when starting up your vehicle, to a faulty belt. In most newer models, this means your serpentine belt, though in older cars the culprit could be one of your v-belts. Keep in mind weather conditions, as overly cold weather could cause the squealing on its own; this will likely subside after your vehicle warms up a bit. However, if the cause is not weather-related, it is important to address the issue early before your safety or wallet are put in danger.

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