Symptoms of a Bad Serpentine Beltby Richard Rowe
Serpentine belts perform a score of important functions. That was actually one of the arguments used against them when they first debuted. Automotive luddites opined that using one belt to run everything didn't offer the safety or redundancy of conventional V-belts, but history tells us which side won that argument.
Often the first sign many notice of a worn belt is squealing -- the nails-on-a-chalkboard screech of a belt slipping on pulleys. But there are subtler signs leading up to that, which you'll only find during routine inspections. Belts wear starts on the toothed ridges, which start out sharp and get gradually worn round over time. Later you might see cracking in the belt, which looks a bit like dry-rotted rubber. This may or may not occur with "glazing," where the smooth back of the rubber has been polished to a high and hard gloss. This glossy surface doesn't grip the pulleys well. More severe wear usually involves fraying around the belt's edges, which often occurs with chipping and overall degradation of the edges. Lengthwise splits along the middle of the belt are typically the last sign before an old belt snaps.