I have a 2003 E46 330d with 120k on the clock. When I drive the car hard for a short while on a warm day the fan comes on and it sounds like a jet (winning sound) reminds me of older 525i's. When I use the aircon that sound almost comes on immediately. Im asking because my mates X5 3.0d does nto do this and a friends 330d also not. I have not yet replaced the waterpump but will soon. No temp issues. Something do with the Fan clutch? The guys at BMW dont seem to know what the hell im talking about.