How to Adjust a Serpentine Belt

Most modern cars that use a serpentine belt have an automatic belt tensioner. This device has an internal spring preset inside that applies the correct tension to the belt automatically, and cannot be serviced. The automatic belt tensioner can fail in time, and need to be replaced. A replacement tensioner would apply the correct preset tension to the serpentine belt. Some imports use a combination of serpentine belts and V-belts. These multiple belt combinations are much like the older cars that used multiple offset V-belts to operate different components in the vehicle separately. Often, jack screws located on the pulley system apply the tension to the belt. Refer to the owners manual of your vehicle, or purchase a repair manual for your vehicle before attempting to adjust the serpentine belt.

Difficulty: Moderate

Instructions

Things You'll Need:

• Ratchet and socket set

1. Refer to the owners manual or repair manual for your vehicle to determine what type of serpentine belt application the vehicle uses. If there is only one belt called the serpentine belt, most often the tension on the belt is achieved through an automatic belt tensioner. If the belt is making noise, or the belt is loose, chances are the belt tensioner should be replaced.

2. Locate the serpentine belt on the vehicle in the engine compartment. Find a location of the belt that is accessible between two pulleys (at the top of the belt if possible), and twist the belt with your hand. Proper tension on a drive belt or serpentine belt will allow you to twist it, and expose the ribs of the belt, but still resist the twisting motion in your hand. If you cannot twist the belt easily, too much tension may be applied, and this can cause premature damage to other pulleys along the belt routing system. If you can turn the belt farther then the half turn to expose the ribs of the belt without resistance, there is not enough tension on the belt. This can lead to the alternator not properly recharging the battery, squeals when driving and premature belt wear.

3. Locate the belt tensioner in the pulley system to test the tension on it if you have this type of serpentine belt application. Most often, moving the belt tensioner in a clockwise fashion will release the tension on a serpentine belt. To do this, a variety of tools may be required. A box end hand wrench, a ratchet or a belt removal tool will work on most belt tensioners. The movement of the tensioner is limited. It will only move enough to relieve the tension on the belt, and allow you to slip the belt off the most accessible pulley. Then the tensioner is designed to spring back into place. When a tensioner fails, it may very well remain in the tension released position, which means the internal spring has failed, and the proper tension is not being applied to the belt. Replacement of the tensioner will be required.

4. Locate the adjusting jack screws for the serpentine belt if you have this type of serpentine belt adjustment. Jack screws are commonly placed near the alternator of the vehicle. The alternator may be easily accessed, or it may require lifting and removing a wheel and fender well to access. Once the jack screws are located, use a ratchet and socket or a hand wrench to turn the jack screws clockwise to tighten the tension on the belt, or counterclockwise to loosen the tension on the belt. Use the twist test on this application to check for the proper tension of the belt.

Tips & Warnings

• Be careful when relieving tension on automatic belt tensioners. Some of these tensioners may be difficult to access, which can lead to the tool being used to relieve them not properly being installed. This can cause the tool to slip and cause personal injury or damage to other engine compartment components, or both.

References

• Tightening Your Serpentine Belt
• Fan Belt Adjustment
• Replacing a Serpentine Belt With a Jack Screw Tensioner

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