3 Causes of Idler Pulley Noise (and Replacement Cost in 2021)

A car engine consists of drive belts or serpentine belt which runs various accessories that are connected to it, such as the power steering pump, A/C compressor, water pump and the alternator. However, it is important that the belts don’t interfere with other components and belts nearby.

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To guide the drive belts, an idler tensioner pulley is used to route them properly around these accessories. This keeps any belts properly aligned and rotating smoothly which ultimately affects the entire internal function of the vehicle.

Most vehicles only need one idler pulley for the engine. In some specialized vehicles, there may be more than one idler pulley. Eventually, the time will come when the idler pulley becomes too worn out or damaged to continue functioning properly.

You will notice when this occurs because there will be various symptoms that will present themselves. One easily noticeable symptom is a squealing or other strange noise coming from the engine area. This will likely be the beginning stages of idler pulley problems or problems with the serpentine belt.

Table of Contents

Top 3 Reasons for Idler Tensioner Pulley Noise

When you hear a noise coming from the idler pulley, it can usually be attributed to one of three causes. Your pulley may wear out, slip, or be damaged altogether. Below is a description of each of these causes in the order that you can expect them to occur.

It is important that you pay attention to the noises because they can go from bad to worse. The lighter noise you hear from the first cause should be enough reason to have your vehicle checked by a mechanic.

Otherwise, the noises will get worse and then lead to more serious problems which will cost you a lot more money to get fixed.

#1 – Pulley Old and Worn Out

tensioner pulley noisetensioner pulley noise

The idler pulley is constantly spinning along with the drive belt. This creates wear and tear on the pulley after years of doing this repeatedly.

The pulley will develop scuffs and other marks on its surface when this occurs. This is when the noises will begin, although they will be less noticeable noises at this point.

 #2 – Pulley Slippage

broken serpentine beltbroken serpentine belt

Idler pulley slippage is likely to follow after it becomes worn out enough. This will cause the pulley to bind and then rub against the engine belt. As a result, there will be squealing noises coming from the engine area that will only get worse until the pulley is replaced.

Not only that, it may also cause other belts and components within the engine to become worn and damaged too.

#3 – Pulley Damage

bad idler pulleybad idler pulley

In extreme situations where the first two causes of idler pulley noise are ignored, the idler pulley will get damaged and ultimately break altogether. The pulley will form cracks and start to break apart a little bit at a time. This will create a chain reaction where the serpentine belt start to tear or completely breaks.

If this happens, then you will have a lot of problems coming from the engine, like stalling and overheating. On top of that, you will have an even louder squealing noise that will be consistent and annoying to everyone in the car and the immediate surrounding area.

Idler Pulley Replacement Cost

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tensioner pulley replacement costtensioner pulley replacement cost

The cost to replace the idler pulley of your driver belt will usually be somewhere between $80 and $200. The cost for the new part should only be anywhere from $40 to $90, while the cost of the labor will be anywhere from $40 to $110. These prices do not include added taxes and fees charged by the auto shop.

Overall, this replacement job is not that expensive to get done. Since the drive belts of the engine are dependent on the idler pulley, you cannot afford to postpone replacing this part after it gets worn out.

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