DIY Guide: How to Replace a Serpentine Belt
March 16, 2017
Average Repair Cost & Time
Avg. Repair Time
60 minutes
Difficulty Level

The serpentine belt in your car, also known as the accessory drive belt, is used to drive a number of accessories on your engine, including the alternator, power steering pump, air conditioning compressor, and even the water pump on some models. The belt is recommended for inspection and replacement between 60k and 90k miles, depending on the manufacturer. A serpentine belt gauge is used to measure belt wear and determine if it is time for replacement. But the belt should be replaced whenever it shows signs of glazing, cracking, or squealing.

Access to the belt and the level of difficulty may differ widely from one vehicle make and model to the next, so do the style of belt and any specialty tools needed to install them. In order to complete this repair it may be necessary to remove underbody shields and closeout panels, or even mechanical components and accessories, in order to gain access to the belt and the tensioner pulley. The steps listed in this article serve as a general guide that will apply to most vehicles. Still, your vehicle may require a slightly different means of access for replacement of the belt.

It may also be necessary to lift and support the vehicle with a jack and jack stands. Failure to follow safe lifting practices can lead to serious injury or fatality.
Parts & Tools Required
  • New serpentine belt
  • Breaker bar
  • Socket set
  • Basic hand tools (for accessory removal)
  • Torque wrench (for lug nuts)
  • Optional: Serpentine belt tool (required for some vehicles)
Before You Begin

Prior to starting repairs, it is wise to follow a few basic safety precautions. While this job does not require a lot of tools, it is important that you make sure to use the proper tools to prevent injury to yourself - or damage to your car. Use personal protective equipment such as a pair of gloves to protect your hands. Shield your eyes with safety glasses or goggles. And be aware of anyone who might be in the area of your repairs.

If you need to lift the vehicle off of the ground to access the serpentine belt, make sure that your vehicle is on a solid, flat surface. Put the vehicle in park and set the parking brake. Place a wheel chock or wood block behind a rear tire to further prevent the vehicle from rolling while you lift it off the ground.

Once you have ensured your safety, and the vehicle is in position for repairs, you are ready to begin

Locate the Belt Routing Diagram

The serpentine belt routing diagram is usually located on a tag in the engine compartment. If it is not found there, it can be accessed in a repair manual, such as Chilton's Online Repair Manual. A quick sketch or a photo of the drive belt system would also suffice. Make sure to understand the routing sequence before you remove the belt.

Belt routing diagram
The Belt Tensioner

The belt tensioner serves to maintain tension on the belt so that it stays in contact with the pulleys. An automatic tensioner will feature a hex head that can be used with a breaker bar and socket (or optional serpentine belt tool) to relieve spring tension on the belt.

The automatic tensioner may instead feature a square hole that will allow a breaker bar to be inserted into the pulley bracket.

Automatic tensioner with square opening for breaker bar
The automatic tensioner pulley on some vehicles is easier to access and actuate with a specialized serpentine belt tool that is used in place of a breaker bar.
Serpentine belt tools
The serpentine belt tool has a thinner profile than a breaker bar

A manual tensioner has a screw-type fastener that will need to be turned in order to relieve belt tension. A lock bolt that holds the tensioner in place will need to be loosened before the tension bolt is turned.

Manual tensioner
Access the Belt

Determine which vehicle components need to be removed for access to the serpentine belt and tensioner pulley. Remove the front wheel(s), relevant underbody shields, and any accessories that might be in the way of the belt or tensioner pulley. For this article we will assume that the vehicle needs to be lifted and a lower shield in the right fender well needs to be removed.

Access to the lower pulleys on this Honda Accord requires that the right front wheel and a lower shield be removed.

Lift and support the vehicle.

If it is necessary to lift and support the front of the vehicle to access the serpentine belt, see our article How to Use a Jack and Jack Stands for information on safe lifting practices.

Safely lift and support the vehicle
A professional technician knows to never crawl under a lifted vehicle unless it is resting firmly on a pair of jack stands!

Remove the shield to access the lower pulleys.

Remove the shield
Serpentine belt location (bottom)

Locate the belt tensioner pulley.

Belt and tensioner pulley location

Using a breaker bar (or serpentine belt tool) rotate the belt tensioner to slacken the belt enough to slide it off of one or more pulleys. Release the tensioner and remove the belt from the vehicle.

Loosen the tensioner pulley
Remove the serpentine belt
Make sure to keep your fingers away from potential pinch points when removing the belt. If the tool slips from the tensioner it is possible to get your fingers caught between the belt and a pulley.
Inspect the System

With the belt out of the way, spin each of the pulleys by hand to make sure none of them are binding. The pulleys should also not wobble from side to side.

Inspect the pulleys

Upon inspection of the old belt, you may notice cracking and worn v-grooves. Compare the length of the new serpentine belt to the old belt. While it is not uncommon for the worn belt to stretch a bit, there should not be a significant difference in the length of the belts.

Compare the old and new serpentine belts
Install the New Belt

Following the pattern on the routing diagram, set the new belt in place. If the vehicle has an automatic tensioner, route the belt around all but one pulley, use the breaker bar (or serpentine belt tool) to turn the tensioner, and slide the belt onto the final pulley. If there is a manual tensioner, run the belt around all of the pulleys before tightening the tensioner bolt enough so there is no more than half an inch of deflection (belt moving up and down when manually pressed by hand) at the center of the longest span of the belt.

Belt routing diagram
Route the new serpentine belt

Once the belt is in place make sure that it is centered on all of the pulleys before reinstalling any accessories or covers that were removed for access.

Replace the shield

Check to make sure the area at the front of the engine is clear. Start the vehicle. Carefully look to see that the belt is in alignment and tracking properly.

Lower the Vehicle

Once the belt has been installed, replace any accessories, shields, and wheels that were removed. Carefully lower the vehicle and torque the wheel lugs before driving.

While this article is directed toward replacement of flat, modern, serpentine drive belts, the procedures are similar to those for older v-belts (also known as alternator belts or fan belts).

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