What Happens If a Serpentine Belt Breaks?

And How Often Does It Happen?

(Image Courtesy of

What Happens If a Serpentine Belt Breaks?

Your serpentine belt is not likely to break. But if it does, the results could be serious.

What Does a Serpentine Belt Do?

(Image courtesy of

The serpentine belt - sometimes referred to as an alternator belt, fan belt, or accessory drive belt - is used to spin, or “drive,” several mechanical components attached to the engine in your car, truck, or SUV. These accessories provide power to important vehicle systems - the electrical system, the power steering system, the cooling system, and even the A/C system. The serpentine belt is responsible for turning all of them.

Consequences of a Worn Belt

The serpentine belt may not be prone to breaking, but it does wear out over time. When a serpentine belt wears - or if the belt becomes damaged or contaminated - the engine accessories may not be able to spin at the proper speed.

For instance, the alternator on the engine is designed to power your vehicle’s electrical system and recharge the battery during operation. If it does not spin fast enough, alternator output will diminish and could lead to dim headlights, loss of some electronic functions, loss of vehicle power, and even a dead battery.

A worn serpentine belt can also lead to poor power steering performance (difficulty steering and premature wear on the power steering pump), insufficient engine cooling (that leads to overheating), and decreased ability of the A/C system to cool passengers on a warm day.

Worn belt vs. new (Image courtesy of Toyota of Yakima)

Vehicle manufacturers recommend inspection and replacement of the serpentine belt between 60k and 90k miles. Advances in material technology allow some belts to last more than 100k miles. Even a worn or damaged belt can survive for quite a while. But if the serpentine belt in your vehicle does break during driving, the results can be terrifying - and potentially dangerous.

Consequences of a Broken Belt

Because some of the accessories on the engine are critical to vehicle performance, and because most vehicles on the road today use a single belt to drive all those accessories, if the serpentine belt breaks while you are driving, system failures can lead to a loss of control on the road.

It is probably not the end of the world if the serpentine belt breaks and the A/C system shuts down. But the same serpentine belt drives the power steering system, the cooling system, and the electrical system.

Consider these consequences of a broken serpentine belt:

  • A broken serpentine belt leads to a sudden loss of power assist for the steering system, where the steering wheel all-of-a-sudden becomes very hard to turn. Imagine that happening in the middle of a busy intersection!
  • A broken serpentine belt stops the water pump from circulating coolant (antifreeze) through the cooling system, and the engine can overheat - anywhere!
  • A broken serpentine belt stops the alternator from generating power to operate the vehicle’s electric (and electronic) systems and recharge the battery. The headlights will dim, the radio will not work, and the battery will go dead!

Because the serpentine belt is responsible for so many critical systems, make sure it is kept in good working order, along with the belt pulleys and tensioner. Sometimes the belt falls off (rather than breaking) because the pulleys and tensioner are worn, damaged, or misaligned. In that case, simply replacing the belt will not fix the problem. The underlying issues will need to be addressed first. The belt may also fall off if it is improperly routed or if it is the wrong belt.

Using a gauge to check for belt wear (Image courtesy of

Have the belt replaced whenever a related component is replaced (a broken belt is often associated with a damaged or seized pulley on one of the engine accessories). And consider regular inspection and replacement of the serpentine belt as a part of routine vehicle maintenance every 30k miles. The belt will wear out in time, but by remaining diligent with preventative maintenance, you can avoid the hassles and dangers of a broken serpentine belt while you are driving.

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