This is a common failure (and it is NOT the fan clutch). Every M103 and M104 I have owned has developed this problem after 100K. In fact, all the components with anti-friction bearings (i.e. ball bearings) should be thoroughly checked at 100K. That means idler pulley bearings, tensioner pulley bearings, alternator bearings, fan support bracket bearings. The only unit that is feasible to renew the bearings on is the alternator, and the Valeo alternators make that virtually impossible. I put a stethoscope on each unit at each service and listen for signs of roughness or noise. I am not sure why this occurs. My theory is that the belt tensioner rubber bush hardens over time and doesn't flex as it should, and vibration and stress is transferred to the various bearings. The water pump, P/S pump don't seem to be a problem.