BMW Repair: 323is shear fan blades, serpentine belt, fan shroud

Question
Hi, Just out of no apparent reason radiator fan blades were sheared off on my
1998 323is 130,000 miles.  I purchased a new radiator fan blade a few
hundred miles ago and again all blades were sheared right off.  It appears
that the blades come off almost all at the same time.  The car was not in an
acident nor was it over reved and their is no sign on the broke off baldes that
they were hitting something causing them to brake off.  Please advise as to
what might be causing the shearing of the radiator fan blades.  Thanks
Matt

Answer
Matt, replace waterpump, pulley, and serpentine belt. Check all pulleies for freedom of movement, wobble, smoothness of turning. Make sure the fan shroud is properly attached and not loose or obstructin anything. Also replace the Metal Fan clutch that the fan bolts to.
-Evan