How to Adjust the Tension on a Serpentine Belt

Written by lynndee marooney
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How to Adjust the Tension on a Serpentine Belt
Most newer cars have automatic tension adjustment for serpentine belts. (car image by Muhammad Umair Tahir from

Stranded on the side of the road is where you will find yourself if your serpentine belt fails. A serpentine belt runs multiple components in a vehicle -- air conditioner, water pump, alternator, power steering and more. A serpentine belt must have the correct tension applied to function properly. A common sign that the belt is loose is a loud whistling sound. By using a belt tensioner gauge, you can adjust the serpentine belt to the correct tension.

Skill level:

Things you need

  • Manufacturer repair guide
  • Tension gauge
  • Wrench
  • Pry bar

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  1. 1

    Review the repair guide for your vehicle to determine the proper tension for your serpentine belt.

  2. 2

    Attach the tensioner gauge to the longest section of the serpentine belt. Pull the belt as far as you can pull it and check the reading on the gauge. Compare this number with your repair guide specification. If you do not have a repair guide or a tensioner gauge, push the serpentine belt in. The rule-of-thumb standard is 1/2 inch of movement for each foot of belt.

  3. 3

    Use a wrench and loosen the tensioner adjustment fastener. Take the pry bar and put one end on the alternator and pull to apply tension to the serpentine belt. Tighten the fastener.

  4. 4

    Attach the tensioner gauge to the serpentine belt and check the reading. If measuring by hand, double-check your reading. If the reading is not correct, repeat the adjustment steps until the correct measurement is achieved.

  5. 5

    Start the engine and make sure the vehicle is running properly. Turn the car off and recheck the measurements. If the belt was not properly seated, the readings may have adjusted once you started the car. Adjust if necessary.

Tips and warnings

  • Replace a serpentine belt that shows excessive signs or wear such as cracking or fraying.

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