Serpentine Belt using a Tensioner


The Serpentine Belt Diagram to the right uses a tensioner and is from a 7.4L big-block. Notice that the smooth side of the belt is always against the smooth surface of the pulley. The teeth/grooves on the underside of the belt will always face toward the crankshaft, and will rest inside of the crankshaft’s track.


What is a serpentine belt?

A serpentine belt is one distinct belt, which is used to drive 1 or more devices in a car, truck, van, or SUV engine. Some of the components driven by a serpentine belt are an air pump, water pump, power steering, air conditioner, and most importantly the alternator. The Serpentine belt is controlled by either a serpentine belt tensioner or an idle pulley.



How does a serpentine belt differ from traditional belt driven engines?

The new serpentine belt, which was invented in 1979 is a much wider belt then the traditional automotive belt. This wider belt and be put under much tighter tension, which removes a lot of slippage and friction experienced by older belt systems. The major benefit to the serpentine belt is that gas mileage is increased due to reduced engine load.


How to change a serpentine belt.

This is a great little movie, which is done by a mechanic and explains how to go about changing your serpentine belts. He points out how most new vehicle have a serpentine belt diagram under the hood. This diagram shows which pulleys each belt goes on and how to thread the belt onto the pulleys. One good thing to note is that when replacing your belt there will be one nut that is revers threaded ie Righty loosy Lefty tighty. Remember this is the case for most drive belt installations.