Has your car’s hood been hotter to touch lately?
Do you keep hearing a strange noise from the engine bay?
These can be bad idler pulley symptoms creating trouble.
The pulley provides a proper route and guides the serpentine belt across various engine accessories. But once it breaks, it can easily lead to vehicle breakdown.
Keep reading to explore the common signs of a bad pulley to help you spot one before it wreaks havoc. We’ll also find out how much it’ll cost you and the perfect time for a replacement.
This Article Contains:
- 8 Common Bad Idler Pulley Symptoms to Watch Out For
- How Much Does an Idler Pulley Replacement Cost?
- 6 FAQs about the Idler Pulley
8 Common Bad Idler Pulley Symptoms to Watch Out For
Here are some tell-tale signs of a bad idler pulley that you shouldn’t ignore:
1. Chattering or Squealing Noise
One common bad idler pulley symptom is unusual chattering, chirping, or squealing sound from the car. A chattering loud noise typically indicates a loose or seized pulley, while a squealing noise means a faulty idler pulley bearing.
The squealing happens when the drive belt (engine belt) rubs against the pulley’s worn-out surface due to insufficient motion from the pulley.
2. Engine Accessories Stop Working
If the idler pulley fails, the engine drive belt will lose alignment and slip. This can cause belt-driven accessories, such as the alternator, AC compressor, and power steering pump, to stop functioning.
You may also notice the check engine light illuminate on your dashboard.
3. Car Overheats
The idler pulley supports your drive belt system by efficiently guiding the drive belt along the pulleys of critical engine components, including the water pump pulley.
The water pump maintains the temperature of your car’s engine. If the idler pulley fails, the water pump pulley will cease to function. Without it, your engine could overheat and cause severe damage to various parts.
If you’ve noticed these symptoms, you should 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 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 it to prevent the engine belt from prematurely wearing out.
5. Excessively Loose Pulley
A functional pulley maintains alignment and moves only slightly. But a loose pulley with no resistance will make a strange noise and cause excessive vibrations. When the pulley is too loose, it can also cause complete belt slippage.
6. Worn Bearing or Pulley
A bad bearing or faulty idler pulley can sometimes break, crack, or come apart. This causes the drive belt to seize or tear, affecting all engine pulleys — AC pulley, water pump pulley, alternator pulley, and power steering pulley.
Gradually, your car engine will start overheating and stalling without a sound drive belt system.
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 idler pulley bearing may have worn out. You may also hear a strange loud noise at normal RPMs if you have a bad bearing.
8. Slow, No Spinning or Binding
A worn bearing inside the pulley can cause it to slow down, stop spinning, or bind up. The pulley will also slow down when the surface isn’t smooth enough for the engine drive belt to move.
If you have been experiencing any of these symptoms, it’s best to replace the faulty unit with a new pulley as soon as possible.
Now, let’s check out how much the replacement can set you back.
How Much Does an Idler Pulley Replacement Cost?
The average cost of idler pulley replacement in most cars is around $160 to $270.
This includes:
- Parts: $20 to $100
- Labor: $140 to $170
However, these costs can be higher for specific car models and make. For example, swapping an old unit with a new pulley in a BMW will cost you about $240 to $345. Meanwhile, if you own a Toyota, it’ll cost between $175 to $210.
Curious to know more about idler pulleys?
Let’s look at some common queries people ask about them.
6 FAQs about the Idler Pulley
Here are answers to frequently asked questions about the idler pulley:
1. What Is an Idler Pulley and How Does It Work?
The idler pulley helps align and guide the drive belt or serpentine belt as it moves through the engine system. This includes components like the AC compressor, alternator, power steering, and water pump.
The idler pulley contains rolled bearings that allow it to rotate when the engine runs. It works with the tensioner pulley to maintain alignment and belt tension, ensuring all connected parts operate smoothly.
2. What’s the Difference Between an Idler Pulley and a Tensioner Pulley?
The idler and belt tensioner pulley work together in a vehicle’s serpentine belt system, serving different roles.
The idler pulley guides the serpentine or alternator belt and maintains alignment around different engine pulleys. In contrast, the belt tensioner pulley works with the spring-loaded tensioner arm to apply and adjust belt tension to prevent slippage.
Note: A bad tensioner pulley can create a chirping or squealing sound similar to a worn idler pulley. So, it’s best to consult an auto repair mechanic to diagnose which part needs repair.
3. How Long Can You Drive with a Bad Pulley?
You shouldn’t drive with a failing pulley.
A faulty 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. Additionally, your engine could also overheat and suffer irreparable damage.
4. When Should You Replace the Idler Pulley?
You should ideally replace an idler pulley every 50,000 to 100,000 miles.
In addition to the pulley, you’ll also have to replace the serpentine belt. That’s because a worn or scored pulley can damage the belt. Eventually, it can also affect your alternator pulley or AC pulley.
So, most mechanics recommend replacing them together.
5. Can I Replace a Bad Idler Pulley Myself?
No, you shouldn’t DIY this replacement.
Replacing an idler pulley requires dealing with the serpentine belt and other vital engine components. One misstep could get the belt misaligned, making it slip.
Moreover, you’ll have to tighten each idler pulley bolt according to torque specifications in the owner’s manual. Over- or under-tightening these bolts can affect the pulley’s function.
Bottom line: Performing these tasks isn’t easy if you’re new to car repairs. So, it’s best to let an automotive mechanic handle it for you.
6. How Can You Make the Idler Pulley Last Longer?
Here are a few things you could do to extend the life of an idler pulley:
- Avoid rash driving to reduce the strain on engine accessories, including the idler pulley and tensioner assembly.
- Get the engine compartment cleaned regularly to prevent dirt or debris from corroding the pulley surface.
- Opt for high-quality parts during replacement, which are more corrosion-resistant and last longer.
- Lubricate the pulley bolt and bearing as per the manufacturer’s recommendations.
- Replace the tensioner assembly as needed to prevent a torn belt.
- Schedule an inspection often to identify signs of pulley wear or belt misalignment.
Restore Idler Pulley’s Spin with AutoNation Mobile Service
The idler pulley is critical for the functioning of different engine pulleys. But when you hear a chirping sound or a squeaking noise from under the hood, it’s time to get it checked.
If you’re not feeling confident about inspecting it yourself, don’t worry!
That’s where AutoNation Mobile Service comes in.
We’re a mobile auto repair solution that offers easy online bookings and a 12-month | 12,000-mile warranty on all repairs, including timing belt and crankshaft pulley repairs.
The best part — our mechanics can diagnose and replace a bad tensioner, idler pulley, or any other engine bay component from your driveway.
Contact us to install a new idler pulley or resolve other automotive issues.