What Are Bad Tensioner Pulley Symptoms?


It can be challenging to identify a bad tensioner pulley because the symptoms are typically not evident during the early stages of wear. However, there are a few telling signs to keep in mind.

Symptoms of a bad tensioner pulley include difficulty starting the car, loud grinding or screeching noises, a loose engine belt, and a lack of power when trying to speed up the vehicle. 

In this blog, we will identify some of these lousy tensioner pulley symptoms as well as the effects a bad tensioner pulley will have on your car. After reading this article, you will be better equipped to identify this issue and know when to take the car to a professional.

Identifying Bad Tensioner Pulley Symptoms

Over time, problems with pulleys will begin to surface. Bearings and pulleys will become loose, resulting in a rattling or squeaking sound that is loud enough to be annoying. 

The noise might seem like it’s coming from a belt and is intermittent at first, but eventually, it should occur when the engine is running.

A bad tensioner pulley will cause noise and can even cause damage to other components if it ultimately fails. While there are no real warning signs of a bad tensioner pulley, there are some symptoms that you can look for that may show problems with this part.

Typical Symptoms of Tensioner Pulley Failure

There are several symptoms of a bad tensioner pulley, which may vary depending on the level of wear and tear that the pulley has sustained.

  • The engine belt may become slack or loose. This can cause the belt to squeal or squeak when the vehicle starts in the morning.
  • There is a grinding noise coming from under the hood, especially when the engine is first started.
  • There is a loud screeching sound coming from the engine compartment, which shows that the belt is about to fail.

If you notice any of these symptoms, it’s essential to take your vehicle to an auto repair shop right away. If left unchecked, a faulty tensioner pulley can cause extensive damage to your vehicle’s engine.

Read: Car Full Service Cost // Whats included?

What Is a Tensioner Pulley?

A car’s engine is a complex system that requires the interaction of several parts to perform correctly. One of the most critical pieces of equipment that keeps your engine running smoothly is the tensioner pulley.

The tensioner pulley is part of the serpentine belt system in modern vehicles. It keeps the proper amount of tension on the belt as it rotates around different components in the engine, such as the crankshaft and alternator.

While the tensioner pulley is an important part, it does have a limited lifespan. Once it goes bad, you will need to replace it quickly to prevent further damage to your vehicle’s engine.

A tensioner pulley is essentially a device used to maintain the tension of a belt or chain. It consists of an integral hub, a bearing, and housing. 

The bearing is mounted to the housing with a series of bolts, which allows the bearing to pivot. As the bearing moves, it places tension on the belt or chain. 

If you have ever seen a belt drive system that uses adjustable pulleys, you are already familiar with how a tensioner pulley works.

Read: Car Diagnosis Cost

Signs of a Broken Pulley

The tensioner pulley is an integral part of your car because it keeps the drive belt from getting worn out too quickly. If it breaks, there will be extra strain on other components like the alternator or water pump, which could lead to them failing prematurely as well.

When a tensioner pulley breaks, all these things can happen:

Squealing Noise

One sign that your tensioner needs to be replaced is if you hear squealing coming from the engine bay when you start your car. This sound indicates that the belt connected to the tensioner is loose, which means that it’s not applying enough pressure to keep the belt tight around the accessory pulleys.

Chirping Noise

Friction between the belt and pulley can cause a chirping noise that can only be heard when you’re driving your car. This is because the sound coming from the friction will have to compete with the noise coming from other components of your engine. A chirping noise could indicate a problem with the tensioner pulley but isn’t a definitive sign as there could be other issues as well.

Read: How Much Is an Inspection for a Car?

Belt Slips Off the Pulley

In extreme cases, the serpentine belt may fall off one or more of its pulleys. This is often caused by a worn-out tensioner that no longer holds enough tension for all of its pulleys. This can be dangerous as it could cause loss of power steering and braking ability and could lead to an accident.

Engine Overheating

The serpentine belt may also drive some of your vehicle’s engine cooling components, such as the water pump, alternator, and power steering pump. If the belt fails, these vital components will stop working, leading to overheating and loss of power steering function.

The Car Dies Immediately

This one isn’t common, but there are certain cars where if the tensioner pulley breaks completely, your car will die immediately. If this happens to you, don’t try to restart your vehicle. Instead, call a tow truck or mechanic so a professional can tend to the issue.

Checking for Symptoms of a Broken Pulley

A failing tensioner pulley can cause the belt to jump off the pulleys or break. Once you discover that the belt has jumped off or been damaged, you must check that the tensioner is functioning correctly.

You can tell if it is not working by watching it while you start the engine. If it is working correctly, the tensioner pulley should move further away from the machine as you start it up. If it remains in place or moves toward the engine, you need to replace it.

The tensioner has a spring mechanism that allows it to move when needed. When this spring breaks, the tensioner may not work correctly and can even cause the belt to jump off or break.

You may spot a problem with the belt by looking and listening to the belt while the engine is running. If there’s any squeal or chirp when you rev the motor, that could indicate a problem with your tensioner pulley. It’s best to get this checked out before it breaks entirely and causes more damage to your vehicle.

Read: What Happens To A Car When The Serpentine Belt Breaks?

What To Do if Your Idler Pulley Is Bad?

A bad or failing idler pulley may cause the following symptoms:

  • Squealing noise from the engine compartment. One of the most common symptoms of an issue with an idler pulley is a loud squealing noise coming from the belt area of the engine. The squealing noise is caused by friction between the components and may appear when you start up your car, and it may get worse as you rev up the engine. This noise will stop when you turn off the engine but return when you start it again. 
  • Slipping or broken drive belts. In some cases, if an idler pulley bearing fails, it can fall on its mounting bolt and allow one or more drive belts to slip off its pulley. If this occurs, you’ll notice a loss of power steering and/or power brakes. A broken drive belt will also prevent your vehicle’s accessories from operating correctly.
  • Degraded performance in extreme weather conditions. Another symptom of a problem with an idler pulley is degraded performance in extreme temperatures, especially during hot weather conditions. 

If you’re hearing loud ticking noises from your engine, or if your engine often stalls when idling, one of the first things for you to do is run through a checklist to determine whether your idler pulley or tensioner pulley might be bad and should be replaced.

Read: 5 Reasons Why A Car Engine Knocks On Startup Then Goes Away


A bad tensioner pulley could make a squeaking, squealing, or screeching sound when you start up your car.

You might notice it getting worse when the engine is cold or hot. A bad pulley can also lead to a lack of oil pressure in each pass of the machine, causing premature wear on other components, such as the camshaft lobes and bearings.

Read: Timing Chain: What Is It and Common Problems?

Leave a Comment