3. Pulley wear
Pulleys are made from plastic, nylon or steel and have either a flat or grooved surface.
Appearance: Flat surfaces should be smooth and free from chips, cracks and dents. Grooved surfaces should be free of chips, cracks, dents and embedded debris within the grooves. The high points of the grooves should not be worn down and be of equal height. Plastic pulleys have fins in sidewalls that should not be cracked or broken.
Cause: Belt wearing into the pulley.
Solution: Replace the complete tensioner. Do not attempt to replace a worn pulley in a used tensioner assembly but always replace the entire tensioner assembly, as part failure will inevitably follow quickly.