Buying the Right Serpentine Belt and Tensioner

Jefferson Bryant

January 05, 2026

4 min read

Jefferson Bryant

January 05, 2026

4 min read

The serpentine belt is a wide, grooved rubber belt that wraps around the pulleys on the engine to spin the accessories at the required speed.

The serpentine belt - opens in new window or tab. drives all of your vehicle's accessories—everything that needs power to run but isn't the engine. This includes the power steering pump, water pump, and alternator. When it's time to replace the serpentine belt and tensioner - opens in new window or tab., there are numerous considerations to take into account before buying—type, materials, warranties, length, and cost.

Types of Serpentine Belts

A mechanic wearing black nitrile gloves points to the tensioner’s bolt-on pulley. — The tensioner may have a bolt-on pulley, but these are not typically replaceable. They are an assembly, so removing the pulley usually destroys the tensioner.

Most serpentine belts - opens in new window or tab. use the same design. But they are constructed from different materials.

Inexpensive belts use neoprene rubber, which has a maximum life of about 50,000 miles.
Premium belts are made with ethylene propylene diene monomer (EPDM) rubber, which is typically good for about 100,000 miles.

The list of premium brands for aftermarket belts includes AC Delco, Bando, Continental, Dayco, Gates, and Goodyear. They are original equipment manufacturer (OEM) suppliers, which means these companies supply car companies with their branded, genuine parts. You can trust that their belts fit as intended.

The same goes for belt tensioners. Quality parts are sold by brands such as AC Delco, Continental, Dayco, and Gates. These brands that make OEM belts also make OEM tensioners.

How much does a new serpentine belt and tensioner cost?

Most belts cost between $40 and $100, depending on the length. Belt tensioners range from $75 to $200, depending on your vehicle’s make and model. We recommend replacing the belt and tensioner together.

Related Parts and Accessories

A mechanic wearing black nitrile gloves holds two sets of pulleys, one old, one new. — Always compare the old part to the new one. If they are not a perfect match, the new unit may not work in your vehicle.

If your engine has an idler pulley - opens in new window or tab., replace it when you swap in the new belt and tensioner. This ensures your accessory drive system is in top working order.

You may need a specialty tool or long-reach wrench to release the tensioner pulley. We recommend buying a belt tensioner tool kit with the most common size open-end wrench fitting and square-drive ends. Most vehicles use a 3/8-inch or 1/2-inch ratchet wrench because they have a square-drive notch for the bearing release.

You might need a special tool to remove the serpentine belt. This varies by manufacturer but is common with European and Japanese brands. This tool, which is often model-specific, simplifies the replacement process. For example, Volvo uses a Torx bit to release the tension, but you can’t reach the tensioner without a long, thin bar. The Volvo tool is a necessity.

Replacing these components on horizontally-mounted engines—as found in most family cars, economy cars, and crossovers—is more difficult because the belt is close to the chassis.

On nearly every vehicle, there is a decal under the hood that shows the proper belt routing. This is important. The accessories are rotation-specific. If you get the belt wrapped wrong, you end up with pulleys that spin in reverse, which can cause major damage. If your vehicle does not have a sticker, check your owner’s manual.

Measuring the Belt

A mechanic wearing black nitrile gloves points out the accessory belt routing pattern on a factory-applied underhood decal. — The belt should be routed as noted on the underhood decal.

If you have an engine that is not in the original vehicle and you do not know what the original vehicle was, or you have added/modified the accessory drive, you could find yourself in a pickle.

There are a couple of ways to get the right belt even in this situation. If you have the original belt that fits, you can measure it. The best way to do this is to pick a point on the belt and mark it as the starting point. Then, set a tape measure to the starting point, and slowly measure, holding the tape measure tight against the belt so it doesn’t slip until you get back to the starting point. This is your outside measurement, noted as the outer diameter (OD). Most belts are noted by the outside measurement or inner diameter (ID).

A socket wrench in the process of unbolting the tensioner. — The tensioner is typically held in place with one to three bolts.

If you do not have an original belt, you can still determine the correct length, but you need a piece of wire or string. Follow the correct routing and wrap the string around the accessories. Make sure the string or wire is inside the grooves on the pulley. Once you have this length, you can measure the length of the string.This is the effective measurement or ID. You can use this to find the belt you need.

When using this method, purchase a larger and smaller size, along with the exact size. This gives you options as sometimes the exact measurement doesn’t quite work. Most belt manufacturers make belts in increments of 1/4 inch.

About the author

Jefferson Bryant

A lifelong gearhead, Jefferson Bryant got his first car when he was two: a Fisher-Price convertible. An industry veteran for over 30 years, Jefferson started in car audio, working his way up to product designer for Rockford Fosgate. He has written nine books and countless magazine articles about automotive technology. Jefferson also produces tech videos on YouTube. His pride and joy is a 1971 Buick GS Convertible with a swapped Procharged Gen V LT1, which he used to drive his newborn kids home from the hospital.

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This article is meant to provide general guidance only. Automotive maintenance, repair, upgrade, and installation may depend on vehicle-specifics such as make and model. Always consult your owner's manual, repair guide for specific information for your particular vehicle and consider a licensed auto-care professional's help as well, particularly for advance repairs.