How To Diagnose A Failing Serpentine Belt

A serpentine belt is an automobile accessory that powers several parts in your vehicle, including:

  • Air conditioning system
  • Power steering pump
  • Alternator
  • Water pump
  • More

It is also known as a drive belt. An OEM Ford serpentine belt is built to last between 60K and 100K miles.

What Causes A Serpentine Belt To Fail?

failed serpentine belt

Serpentine belt failures are typically caused by one of these problems:

  • Normal wear and tear
  • Belt tensioner failure
  • Misalignment of a pulley
  • Defective bearing(s) in the tensioner, idler, or one of the accessories driven by the belt
  • Manufacturing defects in the belt
  • Improper installation

When the belt fails, the accessories it powers will either stop operating or start underperforming. For example, your Ford will lose its power steering, making the steering wheel much harder to turn. Serpentine belt failure while driving can put you in quite a dangerous situation on the road.

That's why you have to inspect your serpentine belt as soon as you notice some signs that it's going bad.

Signs That Your Serpentine Belt Has Gone Bad

A failing serpentine belt can cause these issues:

  • The air conditioner stops blowing as much cold air
  • The power steering suddenly becomes a lot harder to use
  • Squealing noise coming from the engine bay
  • Engine temperature increase
  • Reduced electrical power (i.e. stereo failure or dimmed headlights)

The bottom line is that you need to be ready when your serpentine belt fails. If you neglect the warning signs and let a belt break completely, your engine may suffer severe damage. It's because the serpentine belt will no longer power the water pump. Without a functioning water pump, the engine will overheat.

The good news is it's pretty easy to check and see if your serpentine belt is in good shape. All it takes is a visual inspection.

How To Inspect Your Serpentine Belt

Image Credit: FordTechMakuloco

We based this tutorial on the Ford Fiesta 1.6 HDI engine. If you have another Ford model, the process for accessing the serpentine belt may be different. Yet, the process for inspecting the serpentine belt remains the same across all Ford models.

  1. From the top of the engine, locate the serpentine belt. Grab a flashlight and then give it a visual inspection. Look for any signs of damage, such as:
    1. Cracks
    2. Missing chunks
    3. Abrasions
    4. Rib separation
    5. Uneven rib wear
    6. Obvious breakage
  2. Check and see if the belt is firmly put on all the pulleys. Make sure it's not misaligned on any of the pulleys.
  3. Check the tension of the belt. There are two ways to do this:
    1. Find the longest run of the belt between two pulleys. In the middle of that run, twist the belt. If it turns more than 90 degrees, it's too loose.
    2. Find the longest run of the belt between two pulleys. Put a ruler next to the belt, and then press down on it. If it gives more than 1 inch, it's too loose. If it gives less than 1/2 an inch, it's too tight.

Keep in mind that if the belt is too loose, the tensioner may have failed. This may be the case if the belt hasn't hit the 60K mile mark yet. So it might be a good idea to check the serpentine belt tensioner too.

Need To Replace Your Serpentine Belt?

You'll get a good deal on an OEM replacement serpentine belt with us. At Blue Springs Ford Parts, we offer wholesale prices for OEM Ford parts, including serpentine belts. Look up your Ford model here to see if we have a replacement belt for your car!