What Is an Idler Pulley?

Idler pulleys can help to maintain the appropriate tension in belt systems, such as engine belts that generate movement for serpentine belts that operate the air conditioning compressor and other vehicle accessories.

Idler pulleys are circular disks with grooved rims that support belts. Made of nearly any hard and sturdy material, idler pulleys feature certain key attributes when selecting their materials:

What is an Idler Pulley?

An idler pulley is a gear wheel inserted between other gear wheels in order to change rotation direction or reduce shaft sizes, as well as remove slack from belt systems.

A tracked vehicle employs drive sprockets, idler wheels and track return rollers to move itself over a continuous belt - similar to how conveyor belts move across uneven terrain - but typically operates over rougher surfaces.

An idler pulley is a middle pulley named for its lack of activity; rather than turning the belt, its purpose is to direct accessory drive belt around various major components like alternator, air compressor and power steering pump.

Idler pulleys come in various styles and materials. Toothed idler pulleys feature teeth designed to mesh with the belt's teeth for decreased belt wear and vibration; smooth idlers have no teeth but work with its smooth side instead.

How to Replace an Idler Pulley

Idler pulleys are vital components in maintaining proper serpentine belt tension and alignment, and any issues with one can result in your dryer producing squeals, chirps and difficult turns. Therefore, regular checks for damage or lack of lubrication should be carried out on these pulleys to detect potential issues with bearings that require replacing before continuing use of your dryer.

Replacing an idler pulley is a relatively straightforward process and should be performed as soon as possible in order to prevent further problems from developing. Replacement costs are relatively inexpensive compared to serpentine or accessory belt replacement costs and will quickly stop annoying squeals in their tracks. Most anyone can perform this repair themselves;

Idler Pulley Symptoms

Idler pulleys can often wear out over time due to worn out bearings inside of them, leading them to crack or come apart, potentially leading to torn belts or the engine accessory drive system failing. When this occurs, it may cause engine accessory drive system failure resulting in torn belts being left dangling from a failing vehicle accessory drive system.

One of the hallmarks of an idler pulley failure is a loud, whirring noise when your vehicle is running, along with visible wear-and-tear symptoms on its own such as cracks or grooves in its surface. You can test this pulley manually by spinning it by hand; any resistance or wobbling indicates it may have become stuck and requires replacement. Other symptoms may include check engine lights or warning messages related to accessory function and engine temperature; all indicators that its function has become impaired and requires replacement.

Idler Pulley Repair

Idler pulleys are integral components of your car's accessory belt system, responsible for driving components such as alternator, power steering pump and air conditioning compressor. Loss of tension could cause these parts to malfunction and overheat over time.

Bearings on idler pulleys wear down over time and may seize, causing the pulley to wobble or stop turning altogether. Once this occurs, belts may begin wearing down or becoming dislodged which can lead to engine and accessory issues.

An idler pulley that is no longer functioning properly is one of the primary sources of noise when spinning your belt, rattling and grinding noises can occur as it passes over it. If there is visible damage or wobble to its construction it should be replaced immediately - contact a professional mechanic as soon as possible for diagnosis and repairs to ensure smooth running for both yourself and your car.