this may have been covered here, but i'll try.

had a 98 s70t come in on the hook, owner said don't start it please, i think the belt slipped off. belt done by owner or friend at 100k or so. car now has 119k. front cover sawn through in the belt run outline. turns out the belt tensioner has literally come apart, bearing failure.

i've alway stressed, but not on this board, the rotating parts in the belt drive will not make 210k. the tensioner, idler and the water pump's bearings will get tired. when the belt is changed, either early at 75k or whenever to 105k, replace the other stuff also. all the parts are cheaper than the rebuilding the head when the valves get bent. good luck, chuck.