With cold weather approaching I feel it is time for a discussion of serpentine belts.First I have very rarely seen a belt fail from wear. Failure is usually caused by an idler pulley or a component failure.Cracks do not cause belt failure in fact many manufacturers have grooves in there belts to cool them.Under certain conditions these small cracked pieces can come loose and stick in the groove and cause a belt to come off the pulleys but again this is rare.So when is it time to replace a belt.Anytime it is saturated with any fluid IE antifreeze power steering or transmission.When it looks or feels brittle or hard to the touch.When the cracks exceed more than about 4 to an inch throughout the belt it is time to think about a new belt.Today’s belts are one of the many functions that maintain today’s engines and many are also very difficult to replace so when in doubt get a second opinion and replace it but they are also expensive and oversold at many repair facilities.Belt squeal is also a problem that may require replacing the belt but it is not always the problem.If the noise is on start up turn off the AC or defroster and it may stop the noise.Check for foreign material on the belt Lave soap on the belt will clean it the pumice in the soap cleans.( but use caution)The idler loosing spring tension or being frozen in one position will also cause noisesDO NOT USE belt spray of any kind one of the few uses for WD 40 is to spray on a belt to see if it is the cause of the noise. It will wear of quickly.Once again they are highly oversold so buyer beware that you are not paying for quick lube managers new condo in Florida.