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How to Check Belts on a Car

A mechanic replaces a serpentine belt inside a vehicle.

Most cars built since 1990 have serpentine belts, which wind along pulleys and power various automotive components such as the alternator, power-steering pump, air conditioner and, in certain models, the water pump. Other cars may have timing, drive and V-belts; just like serpentine belts, these are also subject to wear and eventual replacement.

It’s important for car owners to learn how to check belts on a car. Being able to do so will help you detect and prevent problems that may lead to a breakdown if unattended.

Tensioner in place on a model year 1999 7.4L automotive engine, tensioning the serpentine belt.1. Locating the Belt

Lift and secure the hood of your vehicle to locate the belt. Find the side of the engine where the serpentine belt weaves its way through a series of pulleys and is securely held in place with a tensioner and a bolt. Some vehicles include a belt diagram on the leading edge of the engine bay. Otherwise, the diagram may be in your owner’s manual.

2. Looking for Trouble

As belts age, they begin to exhibit telltale signs of wear, including fraying and cracking on the top (smooth) side of the belt. On the bottom (ribbed) side of the belt, you may observe such problems as uneven rib wear, rib damage or even separation. Wear work gloves and use a flashlight to detect problems.

3. Tensing Up

Belts should be firmly secured in place with only a slight amount of give. There are two ways to check belt tension. First, find the longest run of the belt between two pulleys, then hold it with two fingers at the center and twist the belt toward the engine. If it turns more than 90 degrees, then the belt is too loose. The second option is to press down on the middle of the belt. A secure belt should give between one-half to 1 inch and not a bit more.

4. Replacing Spent Belts

If the drive belt needs replacement, refer to the routing diagram before you get started. Purchase a new belt, then observe how the current one wraps around the pulleys. Locate the self-adjusting tensioner, using the removal tool on the tensioner to release it. Remove the old belt. Replace any loose or worn pulleys as needed. Next, using an install tool, secure the belt ribs in the pulley grooves. Lastly, tighten the tensioner, ensuring correct tightness before starting the engine. If you don’t have a tensioner, you may have a stretch-fit belt, which require a special tool for removal and installation.

Driving with worn-out belts can do damage to your vehicle. Make sure to stay on top of this maintenance task before you’re staring down a nasty repair job.

Check out all the belts and hoses available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to check belts on a car, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Image courtesy of Flickr.

Matthew C. Keegan View All

Matt Keegan has maintained his love for cars ever since his father taught him kicking tires can be one way to uncover a problem with a vehicle’s suspension system. He since moved on to learn a few things about coefficient of drag, G-forces, toe-heel shifting, and how to work the crazy infotainment system in some random weekly driver. Matt is a member of the Washington Automotive Press Association and is a contributor to various print and online media sources.

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