Shredding belts.

MZimmerman said
I have it tightened to about 1/4" play. It is pretty snug. It takes about 4 or 5 times to absolutely trash the belt. This really started after using Synthetic Fluid and the 7 blade fan.

Just to test, pull the fan off just to see what happens. Watch the temp gauge close though or install your old fan so you don't overheat.