What does your alternator, water pump, air conditioner, and power steering have in common? On a modern vehicle, they’re all driven by a serpentine belt. What you don’t want is for this long strip of rubber to suddenly break while you’re on the road, as you’ll lose all of these driven accessories and possibly the engine itself.

Capable of lasting 50,000 miles or more, today’s serpentine belts are long-lived. Nevertheless, a quick inspection from time to time can help save you plenty of headaches. Here’s how to check your car’s serpentine belt for wear and tear.

Listen and Learn

Serpentine belts tend to get a little noisy as they wear out with age and use. In fact, belt squeak is usually one of the first signs that your serpentine belt is due for replacement. If your serpentine belt squeaks or squeals, whether it happens upon engine startup or on a constant basis, then it’s time for a more thorough inspection.

While it’s tempting to mask serpentine belt squeal with products like belt dressing, doing so can actually make things worse. Not only are you ignoring one of the many signs of a short life for your serpentine belt, but some products can actually worsen the belt’s condition, making it more likely to fail sooner.

Look for Wear Signs

Most serpentine belts tend to wear out gradually, giving you plenty of warning.

  • Look for glazing on the top of the belt, as well as the grooves. Friction between the belt and the drive pulleys can leave behind glazed spots. Poor belt alignment or a weak automatic serpentine belt tensioner can cause slippage, resulting in glazing.
  • Check for fraying and cracking on the top and edges of the belt, as well as on the belt ribs. It’s not uncommon for serpentine belts to shed material as they age, especially if there’s a problem with the belt’s alignment or a problem with one of the drive pulleys.
  • Check the serpentine belt’s tension by finding the longest run between drive pulleys and pressing down on the middle of the belt. A brand-new and properly routed serpentine belt should be taut and have less than a half-inch of play, whereas a worn-out belt may give by an inch or more.

Using a Wear Gauge

If you’re dealing with a serpentine belt made from ethylene propylene diene monomer or EPDM, then chances are you won’t see the traditional signs of wear and tear mentioned above. Instead, EPDM belts tend to wear out in the same manner as a car tire. That means you’ll find gradual wear that’s hard to spot with the naked eye.

A belt wear gauge comes in handy for discovering signs of wear and tear on an EPDM serpentine belt. With the engine off, place the belt wear gauge on the serpentine belt with the ribs on the gauge fitting into the grooves on the belt. Once the tool is seated, hold it in place with light pressure and try to rock the gauge back and forth.

If the gauge stays firmly seated with little to no movement, then the belt has plenty of life left in it. You may even see the tool rest slightly above the serpentine belt’s surface. If the gauge rocks laterally and/or lies completely flush against the serpentine belt, that means the belt material has worn down enough to merit replacement.