Your Engine 101

Belts and Tensioners

Need to know timing belt symptoms

Belts and belt tensioners work together to keep various components of your car engine running, such as the water pump, alternator, power steering and air conditioner.

The belt winds its way around these various components and when the engine is running, gives them power. The auto belt tensioner lives up to its name and keeps the belt snug, even under different engine speeds and loads.

What's a engine belt?
Engine Belt OverviewA belt (sometimes called a fan belt, drive belt or serpentine belt) is a thin band made of reinforced high-tensile strength cords and synthetic rubber. Belts come in two different types: the traditional V-belt and the serpentine belt. Almost all cars today use serpentine belts.
What's a belt tensioner?
Car Belt TensionerA car belt tensioner is a metal, spring-loaded pulley that attaches to the engine.
What causes a automotive belt to break and what happens when it does?
Over time, even the best belt can break thanks to high temperatures under the hood and constant bending and flexing. Failure of other engine components can also cause your belt to break. When this happens, your car’s accessories stop working. If you continue to run your car engine, more serious damage can result.
What happens when a bad belt tensioner fails?
When a belt tensioner starts to wear, the tension it provides weakens, which in turn affects the belt’s performance and causes it to wear prematurely.
What does a bad engine belt look like?
Here are some photos of belts showing common wear patterns:

Uneven Belt Wear
Uneven Wear
Belt Rib Cracking
Rib Cracking
Belt Abrasion Wear
Belt Pilling Damage
Frayed and Twisted Belt Wear
Belt Rib Separation
Rib Separation
Automotive Belt Fluid Damage
Are there any sounds or timing belt symptoms I should be listening for?
Hissing, grinding, growling, rattling, chirping, squealing, or rumbling noises could be signs that your belt or tensioner is failing. If you hear any of these sounds, see your professional automotive service technician immediately.
How often should my belts & tensioners be checked?
Ask your automotive service technician to check your belts and tensioners every time you have your oil changed. In between time, check your engine belt periodically on your own, for instance when you’re refilling your windshield washer fluid.
Is it difficult to replace a bad belt or belt tensioner?
Generally, replacing a worn belt is very easy and can be completed in about 30 minutes by a professional service technician. It’s not a good idea to put a new belt on a worn tensioner, so ask your technician to replace them at the same time as part of your preventive maintenance plan.

Alternator Belt View
Timing Belt Facts
  • Serpentine and V-belt failure can begin to appear as early as 4 years or 50,000 miles.*
  • 19% of the cars on the road today have a worn belt that should be replaced. That’s nearly 1 in 5!**
Sources: Gates Corporation*, Car Care Council**
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