Adjust Engine Belts

A loose engine belt can cause an alternator or power steering unit to fail.

A loose engine belt can cause an alternator or power steering unit to fail.

Accessory belts apply the engine’s rotation to turn other components. Depending on the design of your car, these belts may be used to power a coolant pump and fan, an alternator, a power steering unit, or air conditioner compressor. On some cars, a single belt wraps around all of these accessories like a serpent, so it’s called a serpentine belt.

Car Words

An accessory belt is a continuous reinforced rubber component that connects and transfers power between the engine and various accessories such as the coolant pump, alternator, air conditioner compressor, and power steering pump. A car may have more than one accessory belt by design. A timing belt connects the crankshaft and camshaft, synchronizing or timing their rotation.

As you can imagine, these reinforced belts get lots of action — and lots of wear. And when they fail, your car quickly can be damaged. Because of all the different accessory belt configurations, I’ll describe replacement in general terms. Refer to your car’s owner’s manual or service manual for specifics.

1. Look at the front of the engine to determine what accessory belts the engine has. Make a drawing of them identifying what accessories they drive. (Some accessory belts will require that covers or brackets be moved first.)

2. To remove most accessory belts, look for and loosen the accessory’s adjustment. It’s typically located on a bracket that attaches the accessory to the engine. Only loosen and move the accessory enough to remove the belt, carefully watching and recording how the belt comes off.

3. Hold the old belt up to the new one to make sure that both are of the same size, width, thickness, and inner edge design. (Allow for minor stretching and wear of the old belt, however.)

4. Carefully thread the new belt on over the pulleys following the pattern of the old belt. Once in place, tighten the accessory adjustment according to the car manufacturer’s specifications. In most cases, the manufacturer will suggest a specific amount of slack in the belt.

5. Start the car and carefully view (don’t touch) the moving belt to make sure it is operating correctly.