Serpentine belts: What you need to know

Last updated: January 1

Four-wheel drive (4WD) is a vehicle system that powers the front and rear wheel axles at the same speed to help gain traction, according to Car and Driver. Drivers have to start a vehicle's 4WD system manually, but a vehicle's all-wheel drive (AWD) system is always on.

4WD systems are traditionally found in large trucks and sport utility vehicles, Edmunds says.

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What is a serpentine belt?

One of the main components of your vehicle's engine is the serpentine belt, which is a long rubber belt that transports power to the engine accessories, according to

What does a serpentine belt do?

The serpentine belt plays an essential role in running your car's systems, explains It powers the alternator, the power steering pump, the air conditioning compressor and, in some vehicles, the water pump. The serpentine belt rotates constantly when the car is running. explains it this way: With a pulley system and a tensioner, the belt uses that rotational power to drive other parts to run various accessories on the car.

Maintenance of the serpentine belt

Maintenance intervals usually range anywhere from 60,000 to 100,000 miles, according to It varies from vehicle to vehicle. It's crucial to perform periodic inspections on your serpentine belt. Check your vehicle's owner's manual to find out the best service interval.

You should start with a visual inspection, says Here's what you'll be looking for:

  • Cracks across the ribs of the belt.
  • If the belt has a nonribbed side.
  • Glazing or shiny spots.
  • Any other signs of belt damage, such as at the edges of the belt frame.

Next, you should use a serpentine belt rib tool — available at most auto parts stores — to take a closer look. Sometimes the belt is worn but you cannot see any of the wear by just looking at it. When you remove the belt, you can use another tool called a belt wear gauge, says Reader's Digest Canada. Setting this tool on the ribbed portion of the belt will reveal how much wear there is.

If you see any oil or coolant saturation on the belt, Firestone Complete Auto Care notes that this means it's definitely time to replace the belt and fix those leaks.

Failure of the serpentine belt

In addition to normal wear and tear, other types of failures can happen, says For instance, a complete failure of a serpentine belt is when the belt breaks or comes off the rollers. This means the accessories are not being driven, so you are going to run into problems. When this happens, you may not have any charging voltage, which means no air conditioner and no power steering. For some vehicles, you may also experience overheating. also points out that you might notice a squeaking noise when a serpentine belt is completely worn out. This usually indicates the belt is worn because it is losing its grip on one or more of the pulleys it is designed to spin.

Replacement of the serpentine belt

For replacing the serpentine belt, all you need is a new serpentine belt and belt tensioner tool, according to AutoZone. For most DIY mechanics, the toughest part of the entire process is getting to the serpentine belt in the first place, they say. They recommend that you take a picture of it with your phone before you remove the old belt. This will make it easier to remember how to route the belt when replacing it.

The first step is to remove the old serpentine belt using the belt tensioner tool, says AutoZone. They caution you to take the belt off carefully, making sure you don't damage the nearby network of pulleys and peripherals. Next, thread the new serpentine belt into position, cranking the tensioner tool and slipping the belt over the tensioner pulley.

Safety considerations

When you are working on your own car, having the appropriate safety gear is just as important as having the right tools. The experts at NAPA recommend the following for every DIY mechanic:

  • Jack stands.
  • Safety glasses.
  • Fire extinguisher.

Make sure your toolbox contains everything you need to make necessary repairs — and protect your safety.