How to Replace a Serpentine Belt
Step by Step Guide for Serpentine Belt Replacement
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.
Parts & Tools RequiredParts:
- 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.
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.
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.
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.
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.
Remove the shield to access the lower pulleys.
Locate the belt tensioner pulley.
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.
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.
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.
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.
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.
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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