How to Put a Serpentine Belt Back on an Alternator


Installing the serpentine belt on the alternator pulley requires providing slack on the belt so it will reach to the alternator and can be tightened over the pulley. This can be done by loosening the tensioner pulley. Older cars required you to use a pry bar to loosen the alternator and tighten the belt. Modern serpentine belts make this task easier through the use of a tensioner pulley, which allows you to loosen the belt with the turn of a socket wrench. Once you locate the tensioner pulley, it will only take a couple of minutes to install a new belt.

Things You'll Need

  • Socket wrench
  • Open the hood to access the engine compartment. Locate the tensioner pulley on the front of the engine. The tensioner pulley is a spring-loaded pulley mounted to the motor that can provide slack in the belt when needed.

  • Loosen the tensioner pulley with the appropriate tool. If the tensioner pulley has a square hole in the pulley, then you will need to insert the socket wrench into the square hole and push down until tension is relieved on the belt. If the pulley does not have a square hole in the side, you will likely notice that the tensioner pulley is located under a metal rod. Push the pulley down by using a metal pipe as leverage on the rod. Some tensioner pulleys require a socket wrench and a socket to loosen the belt tension.

  • Pull the belt around the alternator's pulley once you have released the tensioner pulley enough to provide the slack you need in the belt.

  • Inspect the belt path to ensure it is along all the pulleys. Verify this by checking it against the pulley diagram that is usually displayed somewhere in the engine compartment. If the diagram is not present there, you can find a diagram in the vehicle's owners manual or get one from a dealer or auto parts store. You might also find a diagram through the link in References.

  • Start the car to inspect the belt. Observe the belt to make sure it is tight as it runs along the pulley path.

Tips & Warnings

  • Purchase the belt at the local automotive parts store. The best way to ensure you get the proper size belt is to take the old belt to the store and let them match it up.
  • Use caution when working around the belt. Ensure the keys are out of the ignition before removing and replacing the belt.

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  • Photo Credit timing belt image by Albert Lozano from
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