Signs and Symptoms of a Malfunctioning Automatic Belt Tensioner

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Understanding Auto Service Tasks

Hello, my name is Davey Jerome. Welcome to my site about auto service. When I was a young boy, the first task I learned to perform on my dad’s truck was an oil change. I delighted in letting the old oil flow out into the drain pan and removing the old filter. Adding the new filter and oil seemed to rejuvenate that old truck and ready it for another day of work on the farm. I will use this site to explore the process of performing automotive services on your own. I hope you can use the information on my site to learn about this important task.

Signs and Symptoms of a Malfunctioning Automatic Belt Tensioner

13 July 2016
 Categories: , Blog

The serpentine belt drives multiple peripheral devices in the engine, such as the water pump, alternator, and air-conditioning compressor. The belt can only work perfectly if it is under the correct tension. Therefore, it is kept tight by an automatic tensioner that experiences normal wear and tear just like other parts of the car. It can also get damaged when jammed with dirt or when it cracks. You should suspect a problem with the tensioner in the following cases.

Your Battery Runs Down Easily

The automatic belt tensioner helps run the alternator, which charges your car's battery. Therefore, if the tensioner is malfunctioning, the battery won't charge properly. This will result in your battery running down easily since it won't be fully charged at any time.

Noise from the Tensioner or Belt

Ideally, the belt or tensioner should operate without discernible noise. However, this may change when the tensioner is malfunctioning, and the system may emit rumbling or squealing noises. Since there are many problems that can produce these noises, you will need a professional mechanic's help for a proper diagnosis to pinpoint the source of the noise. For example, the noise may be due to the worn bearings at the center of the tensioner pulley or to a worn belt.

Unusual Belt Wear

If the serpentine belt isn't tight enough due to a malfunctioning tensioner, it will begin slipping. This will result in different forms of unusual belt wear, such as:

  • Glazing on the underside of the belt
  • Accelerated wear of the belt
  • Fraying on the edges of the belt
  • Breakage of the belt (in severe cases)


As mentioned in the introduction, the serpentine belt is responsible for turning the water pump. The water pump needs to run efficiently if it is to cool the car by pushing coolant through the engine block, hoses, and radiator. If the belt isn't tight enough, the pump won't run as well as it should, and the coolant won't flow well enough to cool the engine. The result will be an overheated engine with all the associated effects, such as engine detonation or seizure.

The serpentine belt controls myriad devices in your car, which underscores the need to keep this belt tight and perfectly running at all times. This means keeping the automatic tensioner in good shape at all times. Therefore, take your car for service whenever you notice any of the above symptoms of a malfunctioning tensioner.

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