How To Tell If Idler Pulley Is Bad

The idler pulley creates some rotation points for the engine drive belts to maintain a fixed loop. Idler pullies are designed to guide and tension the engine drive belts to pass through various engine components. The components include the AC compressor, alternator, water pump, and power steering pump. When your vehicle’s idler pulley becomes bad, it will cost you a frustrating and costly repair if you don’t take swift action. Most engines are designed with one idler and one tension pulley which is why they wear out over time and would need replacement.

Symptoms Of A Bad Idler Pulley

Knowing the symptoms of a bad idler pulley will shield you from the dangers of a damaged one. The signs listed below are the signs you should be on the lookout out for.

Squealing Noise

When there is an issue with the idler pulley, the engine belts will make a squealing noise. This could be as a result of a worn-out surface or a pulley that got stuck. when the pulley stops moving, the engine belt rub against its surface and produces a squealing sound.

Worn Out Surface

If the squeaking noise continues after noticing it, check through the idler pulley for possible wear. Continuous rotation exposes the component to friction which encourages wear and deterioration. Change the pulley when you notice unusual marks on it to avoid losing tension and slipping.

Damaged Pulley Or Bearing

The worn-out surface isn’t often as visible as the bearing or pulley wearing out to the point of breaking apart. The belt’s rotation is severely affected and engine function is also distorted. This can force the belt to fall off its slot, leading to stalling and overheating.

Pulley Mounting

In cases where the pulley looks fine and doesn’t need changing, the bracket connecting the pulley may be loose or warped. When this happens, the pulley will wobble or the belt will be forced off the pulley path. A loose bracket is easily replaceable.

Frozen Pulley

A faulty bearing in a pulley can make the pulley freeze or difficult to spin. Taking the belt off the pulley cautiously and rotating it by hand is the best way to determine if the pully is working fine or not. When the pully is difficult to turn, it should be replaced. Follow safety precautions while doing this by ensuring the vehicle is off and the key is not in the ignition.

How Long Can You Manage A Bad Idler Pulley?

The idler pulley plays a vital role in the overall engine operation. For an engine to work accurately, the drive belts and pulleys must be in great shape. Once you notice an issue with your pulley, it is advised to quickly take your vehicle to a repair shop, especially a high mileage vehicle.

A damaged pulley can dislodge the serpentine or drive belt. When this happens, all components depending on the belt for power will stop functioning. These parts may include an air conditioning system, exhaust components, alternator, water pump, and power steering. An accident can happen when the power steering stops working and the engine can overheat when the water pump becomes dysfunctional.

To be on the safe side, the only place you should drive the vehicle to is the closest automobile repair shop. Your first concern should be whether the vehicle is making squeaking noises. Don’t take the risk of negligence once you notice this problem because it may lead to engine failure. Different vehicles have slightly distinct although similar pulley designs which is why their diagnoses are comparable.

Final Note

It is important to know that the idler pulley is responsible for power transmission from the engine to the alternator, air conditioning, and power steering. Regular use causes the idler pulley to wear thereby making it difficult for the belt to turn. Apart from the idler pulley, the bearing can also wear. Look for original products when replacing these worn parts. It is crucial to address this problem promptly to avoid further damage to your vehicle.


Auto, 1. A. (2021, 1 6). 1 A Auto Team. Retrieved from Loud Screeching Sound From Your Car? Might Be a Bad Idler Pulley:

SIGNS OF A BAD OR FAILING IDLER PULLEY. (2021). Retrieved from Auto Parts U:

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