by James Dreamer

Created on: August 03, 2010

Before I begin the body of this article, I want to put forth a word of caution. Moving belts are very dangerous. Do not attempt any service on them with the vehicle running. They can catch you fingers or clothing instantly and cause severe injuries. Also, many vehicles have an electric cooling fan mounted to the radiator which can begin rotating even with the engine turned off and the key out of the ignition. If you must work in proximity to this fan, disconnect the negative battery terminal. Better safe than sorry.

The automotive belts in our cars receive little attention from most of us until they either make noise or fail completely. If they fail, they must obviously be replaced. If they make a squealing noise however, there can be a couple different causes which should be diagnosed and repaired. Here is the procedure to follow that will put a stop to the "fingernails on a chalkboard" like screeching.

A belt squeals because it is slipping against one or more pulleys. The grip the belt provides is not powerful enough to move the pulley surface at the same speed as the belt. In the real world, there is always some slippage, but this is minute and does not produce a noticeable noise. The high pitched sound is caused when the slippage becomes too great. It is important to correct this situation in a timely manner as it will wear the belt much faster than normal.

The most common cause of a slipping belt is improper tension. If the belt is not tight enough, it cannot keep the pulleys rotating when under load. You can check this tension by testing the deflection rate of the belt. With the engine shut off, push on the belt at the center point between two of the pulleys. Some belts must be tighter than others, but if you can move the belt a quarter of an inch or more, the tension should definitely be readjusted.

To do this, you must find the adjustable pulley. This can be an idler or it can be one of the driven components such as the alternator or power steering pump. If you cannot locate it, consult the owners or service manual. You can also find the proper belt tension listed there. Once you locate the component to adjust, loosen the bolt that locks it in place and move the assembly to tighten the belt.

Some systems contain a spring which is calibrated to apply the proper tension to the belt as soon as you loosen the lock bolt. If this is the case, just retighten the bolt making sure the adjustment does not change and you’re finished. If your system does

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