3 Causes of Idler Pulley Noise

Published: April 9, 2022
Last updated: April 14, 2022

A car's engine is driven by drive belts or serpentine belts, which power various accessories such as the water pump, the power steering pump, the A/C compressor, and the alternator. While the belts need to be kept in good alignment, it's also vital that they don't interfere with other belts and components nearby.

Drive belts are properly routed around these accessories using an idler tensioner pulley. This ensures that every belt is aligned properly and rotates smoothly, affecting how the vehicle operates internally.

The engine only needs a single idler pulley on most vehicles. Certain specialized vehicles may feature more than one idler pulley. Over time, the idler pulley will wear out or become damaged to no longer functioning.

Symptoms will present themselves if this occurs, evident through various symptoms. The engine area will squeal or make more strange noises due to the problem. It's probably the start of a serpentine belt problem or problems with the idler pulleys.

Top 3 Reasons for Idler Tensioner Pulley Noise

You can usually isolate three causes of idler pulley noise by observing which one you hear. A worn-out pulley, slipping, or damaged pulley can all cause noise. The following is a list of the most common causes of car problems in order of when they occur.

Keeping an eye on the noises is important because they can worsen quickly. You should have your vehicle checked by a mechanic if you hear the lighter noise from the first cause.

The noises will worsen if you don't stop them, and the problems will become much more serious and expensive to fix.

  1. Pulley Old and Worn Out

Together with the drive belt, the idler pulley constantly spins. When this is done repeatedly for years, the pulley gets worn down.

Whenever this occurs, the pulley will develop scuff marks and other damage on its surface. At this point, you will begin to hear noises, though they will be less noticeable.

  1. Pulley Slippage

As the idler pulley becomes worn out, it is likely to slip. A bind will then occur between the pulley and engine belt, causing the belt to rub against the pulley. The engine area will be filled with squealing noises until the pulley is replaced, only worsening.

Additionally, other belts and parts of the engine may become damaged and worn by this process.

  1. Pulley Damage

The idler pulley can get damaged and ultimately break altogether if the first two causes of idler pulley noise are ignored. Cracks will appear in the pulley, and it will start to crumble slowly. The chain reaction caused by this will cause the serpentine belt to begin to tear or break completely.

As a result, the engine will stall and overheat, causing you many problems. In addition, there will be a squealing sound that is even louder and an even bigger nuisance to everyone in the car and the immediate vicinity.

Idler Pulley Replacement Cost

You will need to spend between $80 and $200 to replace the idler pulley of your driver belt. Labor should cost between $40 and $110, while the new part should only cost $40 to $90. Auto shops may charge additional taxes and fees on top of these prices.

As a whole, this replacement job does not cost that much to get done. To ensure smooth operation of the engine, the idler pulley must be replaced after it wears out as the drive belts are dependent on it.

Are you interested in learning more about cars and their maintenance? Head over to the KeepDriving website and check out our blog post on how to select the right dealer to buy a dodge charger.

Principal Analyst A mechanical engineer by trade, Bobby previously spent over 20 years at automakers giants, where he spent most of his time leading core technology design and operations and the development of new automotive models. He now devotes most of his time to be our go-to guy and Principal Analyst in Keep Driving.
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