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Did you know a single drive belt powers most of your vehicle’s engine accessories? It’s called a serpentine belt because it follows a twisting path to wrap around all the accessory pulleys. Serpentine belts are wide and thin with multiple small V-shaped grooves on one side that fit into matching grooves on the pulleys. The backside of the belt is typically smooth and usually rolls against one or more flat-faced idler pulleys, although it may also be used to drive certain components on some cars.

(Image: AAA)
Engine accessories that are commonly powered by a serpentine belt can include the:

• Air conditioning compressor
• Alternator
• Water pump
• Power steering pump
• Air pump

Essentially, a serpentine belt is to your engine’s accessories what electricity is to your house. If the electricity goes out in your home, appliances stop working. If a serpentine belt goes bad, engine accessories stop working. This can result in something relatively benign, such as no air conditioning, or something much more serious such as a loss power steering or a lack of coolant circulation, which can lead to engine overheating and expensive damage.

How to Know When to Replace a Serpentine Belt

With older, neoprene rubber serpentine belts, it was easy to spot cracks and worn areas with a visual inspection. These days, manufacturers make serpentine belts of much sturdier ethylene propylene diene monomer rubber that rarely shows cracks. Damage and wear to EPDM rubber serpentine belts is only identifiable with a special tool or a smartphone app, both of which measure actual wear on the belt ribs.

While modern serpentine belts can run for over 100,000 miles without any visible wear, even as little as a five percent material loss leads to belt slippage and increased wear and tear. That’s why professional technicians recommend replacing serpentine belts every 50,0000 to 60,000 miles. If your vehicle uses an automatic belt tensioner, it’s a good idea to replace it at the same time to make sure the new belt stays in proper contact with the pulleys at all times.

When Your Belt Goes Bad

Serpentine belts are usually inspected during regular vehicle service appointments, but don’t let that stop you from asking a technician to check yours out. For a little extra peace of mind, consider signing up for AAA Roadside Assistance. If you should find yourself on the roadside with a failed serpentine belt, flat tire or other vehicle emergency, our skilled problem solvers are available 24/7 to provide help at your location.
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