How To Diagnose A Failing Serpentine Belt

A serpentine belt should last around 75,000 miles. Sometimes it will wear out faster. A lot of different problems could cause it to wear out faster, including:

  • A misaligned pulley
  • A defective belt tensioner
  • Bad bearings in accessories such as the alternator

So when a component driven by the serpentine belt begins to fail, the serpentine belt will also begin to fail. Over time, the belt will fray or stretch.

Many mechanics recommend checking all your belts on a regular basis. It's common to check the serpentine belt during every oil change. If you haven’t checked your serpentine belt in a while, and if you notice symptoms of a bad belt, then an inspection is in order.

The Symptoms Of A Failing Serpentine Belt

Worn belt

Image Credit: Samarins

Have a hunch that your serpentine belt is failing? Keep an eye out for the following symptoms:

  • Squealing noise coming from the engine bay
  • Low power from the power steering system
  • Dim headlights
  • Overheating engine

What Happens When You Don’t Replace Your Serpentine Belt

If the serpentine belt is loose or broken, many parts will stop working. For instance:

  • The alternator will no longer keep the battery charged enough
  • It will become harder to steer the car
  • The water pump will lose power and cause the engine to overheat

How To Check Your Serpentine Belt

Check belt

Luckily, checking your serpentine belt is an easy task to do at home. You only need to:

  • Give the serpentine belt the eyeball test to see if there are any cracks or fraying
  • Check the serpentine belt's tension
  • Check related components for good measure

Here's an overview of the process:

  1. Open the hood.
  2. Grab a flashlight and then visually inspect the serpentine belt. Look for cracks, fraying, cuts or breakage.
  3. Find the midway point between two pulleys. Next, move the serpentine belt back and forth with your fingers. Measure the amount of play with a ruler. (There should be about 1/2" of play. If there's less than 1/2" of play, then the belt is too tight. If there's a lot more than 1/2" of play, then the belt is too loose.)

Note that many Mazda models have a transversely (sideways) mounted engine. In that case, the belt will be on the right side of the engine compartment instead of in the front.

Other Parts To Check

Belt parts

If your serpentine belt is frayed or stretched, then there may be an issue with a related part. It's a good idea to check the following pulleys and pulley-related components:

  • Idler pulleys
  • Camshaft
  • Tensioner
  • Air conditioning compressor
  • Water pump
  • Alternator
  • Power steering pump

Replacing Your Serpentine Belt

If you’ve determined that you need to replace your serpentine belt, grab a few basic tools. Here's an overview of the replacement process:

  • Relieve the tension on the old belt
  • Remove the old belt
  • Install the new belt

It’s an easy and straightforward task that should take you no more than an hour.

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