Drive Belt Tensioner

Drive Belt Tensioner

An internal combustion engine is a big energy converter that turns gasoline into motion so that your car can move. When running, the engine uses one or more rubber belts, known as drive belts, to operate several devices, such as an alternator, water pump and some others, housed on its side or front.

Unlike older vehicles that usually feature several drive belts, the majority of today’s vehicles utilize one drive belt, called a serpentine belt, to run all necessary devices. It winds its way around all gadgets, including an alternator, air conditioning compressor, water pump and power steering pump, and uses the power of the engine to drive the devices. 

To keep your engine’s devices running properly, a drive belt or a serpentine belt must be under the right amount of tension. This is when your drive belt tensioner comes into play. 

The purpose of a drive belt tensioner

To prevent your drive belt from coming off and slipping, the right amount of tension should be applied to the belt. This is exactly what your drive belt tensioner does. It provides as much tension as needed to ensure proper operation of your engine’s accessories while preventing them from premature wear that may be caused by excessive tension.

Not all drive belt tensioners look the same. Here are the most common types of them:

Manual pivot tensioner

This is the oldest type of drive belt tensioners. By design, it’s a slotted bracket that is attached to an engine-driven device, for example, an alternator. To apply the proper tension to the drive belt, you need to move the device along the slot and once you find the right position tighten the bolt that holds it. Keep in mind that a manual pivot tensioner should be readjusted from time to time since a drive belt gets stretched over time. The good news is that it will serve you for years to come.

Spring tensioner

As its name says, a spring tensioner features a spring mechanism inside the pulley’s housing. A drive belt runs through this spring-loaded pulley, receiving the required amount of tension applied. Even if the belt wears over time and increases in length, the spring-loaded mechanism will compensate for this.

Hydraulic tensioner

A hydraulic tensioner operates similar to a shock absorber, using hydraulic oil to apply tension to a drive belt. This type of belt tensioners provides the most accurate amount of tension required for the proper operation of engine-driven devices, however, it may eventually leak, loosing its ability to apply tension. 

How can I find out that my drive belt tensioner is out of service?  

A faulty drive belt tensioner may alert you of its problems with the following signs:

  • Abnormal noise from your drive belt, especially at low RPMs
  • The engine looses the drive belt
  • The battery warning light turns on
  • The drive belt runs out of center
  • Squealing noise from the hydraulic or spring-loaded tensioner
  • Damage to the spring tensioner
  • Leaking hydraulic tensioner
  • Your drive belt is damaged or worn out
  • You can push down the belt more than an inch

How can I fix a bad drive belt tensioner?

In case it is a manual pivot tensioner, you may adjust it with a wrench in less than no time. If the drive belt shows any signs of wear, it should be replaced.

Spring and hydraulic tensioners are not repairable. Both of them must be replaced if they’re cracked or worn out. The drive belt should also be replaced since it’s quite possible that it has got damaged due to the bad drive belt tensioner. This will save you a lot of headache in the long run.

Installing a new drive belt tensioner should not be a tricky experience if you have been working on engines before. Otherwise, you should hire a professional mechanic to have the job done properly. He will also check that the belt runs at the center of all pulleys, and they are properly aligned.