Blog Car Care Advice 8 Bad Idler Pulley Symptoms You Should Be Aware Of
Car Care Advice

8 Bad Idler Pulley Symptoms You Should Be Aware Of

Looking for a mechanic near you for maintenance or repair? AutoNation Mobile Service brings the shop to you. Get a free instant quote today.
Get a Quote

Every car lover knows the importance of regular oil and fluid changes. But, hidden beneath the hood, a silent troublemaker often escapes our attention — a bad idler pulley

This small yet essential part can throw a wrench into your vehicle’s well-being when things go south. Surprisingly, diagnosing issues with this engine component is easy if you pay attention to the bad idler pulley symptoms. 

In this post, we’ll decode how to spot a failing idler pulley, the replacement cost, and more. 

This Article Contains: 

Let’s begin! 

8 Common Bad Idler Pulley Symptoms to Watch Out For

Here are some tell-tale signs of a bad pulley that’ll help you take proactive measures:

1. Chattering or Squealing Noise

One common bad idler pulley symptom is unusual chattering, chirping, or squealing noise from the car. 

A chattering noise typically indicates a loose or seized pulley, while a squealing noise is a sign of a faulty bearing. The squealing is produced when the drive belt (serpentine belt, alternator belt, or engine belt) rubs against the pulley’s worn-out surface due to insufficient motion from the pulley. 

2. Car Overheats

Your car overheating is a severe symptom that could also result from a bad idler pulley. 

The idler pulley ensures the drive belt system has enough tension to drive the pulleys for critical engine components, including the water pump pulley. The water pump is responsible for maintaining the engine temperature. Without it, your car could overheat and lead to complete engine failure.  

3. Engine Accessories Stop Working 

If the idler pulley fails, the engine drive belt will lose the belt tension and can come off. This can cause the engine-driven accessories, like the alternator, AC compressor, power steering pump, etc., to stop functioning. You may also notice the Check Engine Light illuminate on your dashboard. 

If you notice any of these symptoms, the next thing to do is look for the following visual cues. 

4. Corroded Pulley Surface

A normal idler pulley should have a smooth surface. However, continuous rotation can corrode the idler pulley’s surface over time. This leads to visible scoring marks due to contact with the belt. If you notice scoring marks on the pulley, you should replace the pulley to prevent the engine belt from losing tension and slipping. A corroded idler pulley will also cause premature wear on the engine drive belt. 

5. Excessively Loose Pulley 

Another sign to look for is an excessively loose pulley. A normal pulley will move only slightly, but a loose idler may make a chattering noise and cause excessive vibrations. This could also be due to bad bearing inside the idler. If the pulley is excessively loose, it could cause the belt to come off.

6. Worn Bearing or Pulley

A bad bearing or faulty pulley could sometimes break, crack, or come apart. As a result, the belt will seize or you may end up with a torn belt, affecting all the engine pulleys — AC pulley, water pump pulley, alternator pulley, and power steering pulley.

Consequently, an engine without a drive belt system will quickly overheat and stall. 

7. Excessive Spinning 

A working pulley should spin for a few revolutions without resistance and then stop. To confirm a failing pulley, check if it turns more than a few rotations. If so, the pulley bearing may have worn off. You may also hear some noise at normal RPMs if you have a bad pulley bearing. 

8. Slow, No Spinning or Binding

Like excessive spinning, slow or no spinning or binding indicates a bad pulley. Moreover, if the faulty idler pulley is on an engine component, like the alternator or water pump, it’ll also need to be rebuilt or replaced.

If you have been experiencing any of these symptoms, it’s best to replace the faulty idler pulley as soon as possible.
Let’s check out how much the replacement can set you back. 

How Much Does an Idler Pulley Replacement Cost? 

Whether you own a Honda Motor Company vehicle or a Toyota, a replacement idler pulley usually costs between $20 and $100. This cost could vary depending on your vehicle’s make and model. 

The labor charges to install the new pulley can range from $100 to $300 since the accessibility of this engine component can vary in the engine compartment based on your car’s make.

Now that you know whether or not you need an idler pulley replacement, we’ll address some other common questions you might have. 

5 FAQs about the Idler Pulley

Here are answers to frequently asked questions about the idler pulley: 

1. What’s the Difference Between an Idler Pulley and a Tensioner Pulley? 

The idler and belt tensioner pulley are two distinct components in a vehicle’s serpentine belt system, serving different roles.

The idler pulley guides the serpentine belt or alternator belt and maintains alignment around different engine pulleys, while the belt tensioner pulley applies and adjusts belt tension to prevent slippage. 

Note: A bad tensioner pulley can also cause a chirping or squealing noise from your car. 

2. What are the Common Causes of a Failing Pulley?

An idler or tensioner pulley could go bad due to: 

3. How Long Can I Drive with a Bad Idler Pulley?

Technically, you can continue to drive with a bad idler pulley until it fails. 

However, we wouldn’t recommend it, as a failing idler pulley could cause the drive belt to slip or snap off, bringing critical engine accessories like the alternator and power steering pump to a halt. Your engine could also overheat and suffer irreparable damage. 

4. When Should I Replace the Idler Pulley?

You should ideally replace an idler pulley at 80,000 to 160,000 kms. However, the replacement time also depends on the replacement of the timing belt and serpentine belt. 

That said, an idler pulley or its bearings can wear out sooner and must be replaced at the earliest. If you don’t replace a faulty pulley, it can damage your power steering, alternator, or AC compressor.

5. How Can I Make the Idler Pulley Last Longer?

Here are a few things you could do to extend the life of an idler pulley: 

Wrapping Up 

The idler pulley is critical for the functioning of different engine pulleys. So, if your vehicle has been showing bad idler pulley symptoms, you should book an auto service as soon as possible.

What if you can get the pulley checked right in your driveway? 

Fortunately, AutoNation Mobile Service’s mobile mechanics are at your service seven days a week. Our expert will come to you to replace a bad tensioner, idler pulley, or any other engine bay component. Plus, we offer a 12-month | 12,000-mile warranty on all repairs. 

Contact us today to keep your engine and its accessories in top condition.