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Summary
  • The idler pulley is a component that supports the movement of your vehicle’s drive belt.
  • Common symptoms of a malfunctioning idler pulley include corrosion on the pulley’s surface, chattering and squealing noises, and slow spinning.
  • Recommended idler pulley brands include Replacement, Gates, and Dayco.

Your engine has drive belts (or a serpentine belt) which transfer power to different accessories like the power steering pump, A/C compressor, water pump, and alternator. The idler pulley is a component that helps provide tension and keeps your drive belts aligned and guided. Let’s take a closer look at how this part works and when you should replace it.

What Is an Idler Pulley?

An idler pulley, also known as the accessory belt idler pulley, supports the movement of the drive belt. It may come with either a ribbed or smooth surface. It comes with rolled bearings that allow it to rotate.

Most vehicles only need one idler pulley for their engine. However, some specialized vehicles have more than one idler pulley installed.

How Does an Idler Pulley Work?

To fully understand the function of an idler pulley, let’s look at how the whole mechanism works. If you own a modern vehicle, it probably has one serpentine belt rather than multiple V-belts.

Your serpentine belt wraps around your engine accessories. The belt also connects to the crankshaft pulley, which transfers power to various engine accessories.

car engine with drive belt and idler pulleys
To fully understand the function of an idler pulley, let’s look at how the whole mechanism works.

When your vehicle is in motion, the engine crankshaft pulley will allow your serpentine belt to turn, driving various engine accessories via the accessory belt idler pulley. Your engine accessories will continue to operate for as long as the mechanism rotates.

Symptoms of a Bad Idler Pulley

Issues with your idler pulley shouldn’t be taken lightly. A bad pulley can damage other related components in the long run. You’ll end up spending more on repairs than what was originally needed. Have your vehicle checked right away if you notice any of these symptoms:

Noisy Idler Pulley

Chattering and squealing noises are often associated with a drive belt or serpentine belt system fault. These often indicate that the idler pulley is loose. On the other hand, a squealing noise might mean your idler pulley bearing is overheating.

If you hear unusual noises from your engine, have it checked by a certified mechanic. A professional will be able to determine whether the culprit is a bad idler pulley or if something else needs fixing.

Corrosion on the Pulley’s Surface

A pulley that’s in good condition will have a smooth surface. Rust or corrosion damage on the pulley’s surface can negatively affect the operation of your serpentine belt.

Loose Idler Pulley

An excessively loose idler pulley will produce a chattering noise. Bad bearings can cause your pulley to become loose. Make sure to inspect the bearings for any faults as well.

Slow Spinning or Binding

In worst cases, a bad pulley will spin very slowly or not spin at all. Slippage can also cause binding, leading to excessive contact with the engine belt, producing a squealing noise.

Engine-Driven Accessories Stop Working

If the idler pulley fails completely, the serpentine belt will likely come off, causing the engine-driven accessories (i.e., alternator, air conditioning compressor, etc.) to stop working.

How Much Does an Idler Pulley Replacement Cost?

An aftermarket idler pulley typically costs anywhere between $20 and $100. Some pulleys can be priced higher depending on brand and other product specifications. Expect to spend another $100 to $300 on labor to have the pulley installed.

Rates vary depending on the specific vehicle you own and the rates in your area. Remember to take into consideration other expenses like taxes and related repairs.

Best Idler Pulley Brands

different idler pulley brands
There are a lot of aftermarket brands that sell good idler pulleys for various vehicles, so finding one for your ride will surely be a breeze.

If your idler pulley is faulty, you don’t need to worry. There are a lot of aftermarket brands that sell good idler pulleys for various vehicles, so finding one for your ride will surely be a breeze. Here are some of the best brands on our list:

Replacement

When it comes to aftermarket OE parts, you can always trust Replacement. The brand manufactures high-quality idler pulleys for various makes and models. All Replacement parts and accessories are manufactured to OE specifications in world-class facilities to guarantee excellent fit and performance.

Gates

Gates manufactures high-quality idler pulleys that won’t break the bank. Their heavy-duty and wear-resistant idler pulleys are engineered to help reduce friction and vibration on your drive belt system.

Dayco

When it comes to top-notch idler pulleys, you can never go wrong with Dayco. The brand manufactures a wide array of pulleys equipped with various bearing configurations to make them more durable. Dayco uses computer-aided design (CAD) and finite element analysis to guarantee premium design and superb structural integrity.

Get a High-Quality Idler Pulley Replacement for Your Ride

Don’t think twice about replacing a bad idler pulley, as it can cause your serpentine belt to come off and engine-driven components like the alternator and water pump to stop functioning. For a top-notch idler pulley replacement, shop online here at CarParts.com.

Order a top-notch aftermarket idler pulley without leaving your home. Go to CarParts.com using your mobile device and input your ride’s details into our user-friendly vehicle selector to view compatible parts. Choose from our selection of idler pulleys sourced from top brands in the industry. All our products passed strict quality control tests, so you can be sure you’re getting a durable replacement.

Need to get back on the road as soon as possible? Our distribution centers are strategically located across the country, so expect your order at your doorstep in as fast as two business days. We also have a round-the-clock customer service team ready to assist you in case you have questions about your order.

Keep your daily driver in good running condition by replacing your aftermarket idler pulley now. Check out our catalog today.

About The Authors
Written By Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Reviewed By Contact Center Manager and Technical Reviewer at CarParts.com

William “Bill” Guzenski has produced hundreds of how-to videos for the automotive community. He’s an ASE Certified Master Automobile Technician, and is affiliated with the Specialty Equipment Market Association (SEMA). He loves attending race events and car shows throughout the country, as well as traveling in his 40-foot motorhome, exploring abandoned mines and ghost towns.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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