Serpentine Belt Tensioner

What is a serpentine belt tensioner and where is it located?

Most cars and trucks on the road today use a serpentine belt to transfer power from the engine’s crankshaft rotation to the multiple accessories that are bolted to the vehicle’s engine, such as the alternator, power steering pump, radiator cooling fan, and A/C compressor, among others. This drive belt needs to have just the right amount of tension applied to it to function properly, ensure long belt life, and prevent excessive strain on the accessories. That’s where the serpentine belt tensioner comes in.

A serpentine belt tensioner, also commonly referred to as an accessory belt or drive belt tensioner, is a spring-loaded or hydraulic automatic adjusting device that—along with pulleys—is responsible for generating and maintaining the proper amount of tension on a vehicle’s serpentine belt so that the belt can keep all of the different engine accessories connected to it operating smoothly and effectively.

How do I know my serpentine belt tensioner needs to be replaced?

Over time serpentine belt tensions may weaken causing the belt to lose tension; this may result in belt slippage, squealing and premature belt wear. A loose belt could potentially work its way off a pulley causing it to snap or even fall off completely, leaving you stranded. However, too much tension will result in an excessively tight belt, which will decrease the bearing life of the accessories. This could force you to replace parts such as your alternator or water pump well before its normal service life expectancy. Another common failure point would be the tensioner pulley bearings; over time these bearings will eventually fail. Symptoms of bad pulley bearings would be wobbling or play in the pulley, usually accompanied by noises such as a squeak or squeal. It is recommended to inspect the tensioner and idler pulley every 50,000 miles or whenever replacing the serpentine belt. If your vehicle is displaying any of these symptoms, you may need a replacement accessory belt tensioner assembly.

Can I replace a serpentine belt tensioner myself?

Replacing your vehicle’s serpentine belt tensioner assembly may be easier than you think and can usually be done with basic hand tools. Some applications may require using a special serpentine belt tensioner tool for accessing the tensioner bolt to relieve belt tension, which is necessary to remove the belt. For the most part, the process can be as simple as loosening tensioner bolt and sliding the belt off. To reinstall the belt, it's a good idea to follow a serpentine belt diagram specific to your vehicle so that the belt is reinstalled on the pulleys correctly.