Idler Pulley VS Tensioner Pulley – What are the Differences?

Last Updated on December 31, 2022 by Leepu Da Maxim

An idler pulley is used to guide or redirect a belt or chain while a tensioner pulley applies tension to a belt or chain. An idler pulley is mainly used to change the direction of the belt. On the other hand, a tensioner pulley is used to maintain proper tension on a drive belt.

Key Takeaways

  • Idler pulleys are typically mounted in a fixed position, while tensioner pulleys are mounted on a pivot or hinge position
  • If there is any problem with the idler pulley then it can produce various noises like squealing, grinding, or scraping sounds
  • If there is any problem with the tensioner pulley then it can produce various noises like screeching, rattling, grinding, or buzzing noises
  • Tensioner pulleys are typically found on engine accessories such as the alternator, power steering pump, and air conditioning compressor

Idler Pulley VS Tensioner Pulley – Key Differences

Idler PulleyTensioner Pulley
The idler pulley is not mounted on a bolt. This component is mounted on a fixed structure  The Tensioner pulley is mounted on an adjustable bolt  
They are in charge of moving the straps to different placesTension pulleys provide pressure to a belt.  
Idler pulley provides efficient and smooth rotation point  This operation drives other pulleys while the attention on that belt is relieved  
The idler pulley is used for routing purposesThe Tensioner pulley provides tension to the belt

What Does A Bad Idler Pulley Sound Like?

As with any vehicle component and some symptoms you may notice when an idler pulley is malfunctioning. So paying attention to these types of symptoms will allow you to know the ideal time to replace defective pulleys.

This is an important procedure since a defective pulley could deteriorate other components on the same vehicle much faster. As a result, you may notice that a drive belt tensioner produces more noise during operation.

In particular, this squeaky noise will be even more noticeable when you start the vehicle. Once the user hears this symptom then it will be necessary to apply the necessary maintenance and repairs. In particular, an idler or idler pulley is a major component in an engine. That’s why these components should be repaired as soon as possible.

To be able to apply this repair, a skilled mechanic with the appropriate knowledge is needed. If you can buy replacement parts, you will not be able to perform the component exchange procedure.

This requires a set of tools that only mechanical technicians have. Additionally, it could be somewhat dangerous to perform this procedure when you are just a beginner in mechanics.

Generally, those who seek to change these components face some dangers. Other symptoms are important to consider. Thus, another major problem could be excessive belt wear.

So, an idler pulley with these problems is likely to be much closer to breaking down for good. So, it is necessary to make the necessary repairs before the pulley breaks down for good.

Another common symptom is that some belt-driven accessories may fail. Here, we can include some important components such as the AC compressor, the water pump, and the alternator.

Each of these components needs the proper functioning of the belt to operate. Here, it is most likely that a belt tensioner will allow the belt to break. So, this will certainly disable the air conditioning system, the battery and the electrical system will be dead or the vehicle will overheat.

If you wait too long for that, then the number of repairs that will be necessary for your vehicle will increase considerably. You may even be able to avoid spending too much money when you apply the necessary maintenance on time. 

How Long Can You Drive With A Bad Tensioner Pulley?

In this case, it is necessary to consider that once the squeaking starts when you start your vehicle the repair maintenance is necessary. Of course, the amount of time you will be able to drive with these issues can vary considerably.

Here, we can mention that you may be able to drive for a long time with damaged idlers. So after a few months, the idler pulleys may be malfunctioning but not yet broken.

Conversely, if you use your vehicle very intensively, then the idler pulleys can break down within a few days. So, it is really necessary to consider each of these aspects since you will need much more money to make the repairs.

This can also happen with other components of your vehicle that will be affected by the idler pulley. In particular, the idler pulley allows other engine components to function properly. Some of the most common problems your vehicle can experience are overheating or the death of the battery and electrical system.

As you may notice, waiting too long will only make things worse for your car. Here, it is necessary to take into account that the air conditioning system, the water pump, and the rest of the components related to the idler pulleys are expensive. The car could overheat when you’re driving.

Simply put, excessive heat in a car only leads to faster deterioration of the various engine components. Temperatures too high for a car can easily deform metal engine components.

Of course, this is not recommended and with enough time your car could be permanently disabled. At the same time, it is also necessary to consider that the different components of a vehicle have a certain lifespan.

Once the life of a vehicle is exceeded then the various component failures may begin to appear. Of course, if the user decides to apply moderate use, a useful life could be extended. That is why it is always advisable to apply proper maintenance to a vehicle at the exact moment.

How Much Does It Cost To Fix A Tensioner Pulley?

To be able to carry out the necessary repairs and maintenance, you will need a certain amount of money. Here, it is necessary to take into account that the performance problems of your vehicle will be noticed when a tension pulley is damaged.

So, to get a replacement part, you will need from $125 and you might even need up to $380. Of course, here it depends on the quality of the product, in combination with other important factors that must be taken into account.

In the same vein, it is also important to consider the labor required to perform the exchange of parts. Here you could need between $50 and $155 approximately. So, in the most expensive case, you might need more than $500 depending on the type of vehicle. 

If you wait too long to change the idler pulley, then another component may deteriorate as well. So, if you wait too long, you’ll need more money to replace the various parts of the vehicle.

Also, if the water pump does not work properly, overheating in the engine will be very harmful. Here all the components of the engine can be deformed and deteriorated much more quickly.

To this, we must also add that the electrical system can die along with the battery. Also, the air conditioning system could stop working, which is not convenient if you are in the summer. 

Can You Drive Without An Idler Pulley?

Here, it is important to keep in mind that the idler pulley is one of the essential components for the proper functioning of a car. So, it will not be possible to drive a vehicle without the idler pulley.

In the best-case scenario, you will have to face a lot of problems related to this component. In particular, the belt drive system needs the idler to function normally.

Here, it is necessary to consider that you will not be able to drive a vehicle, use the air conditioner, or even start it. In turn, it is necessary to apply all necessary repairs when an idler pulley or a tension pulley begins to fail. 

This is because many components of a car depend on these pulleys to function. So, if any of these pulleys deteriorate, then other vehicle components will begin to fail as well. In other words, you will need more and more money to perform all the necessary repairs and maintenance to your vehicle.