From new, my car had a mild whistle at high fan speed. I considered this a fault, but did not do anything as I suspected that I would be told it was normal.
Recently the whistle was replaced with a mild grating noise at high fan speeds. Like a mild flapping or something. In my opinion this was clearly outside of operating parameters.
I sent the car in and was told that there was nothing wrong.
I strongly objected and told them to compare it to another X3, they came back and agreed that it was not the same.
Further investigation found that one of the fan blades had sheared off.
The replaced the blower unit and everything is now quiet...
F25 X3 xDrive 35d M Sport Alpine White, Black Nevada Leather, Speed limit info, TV, Prof. Nav & Speakers, HUD, M Sport steering wheel, Sport gearbox, BMW Apps, Internet, VDC, Comfort with Powered boot, Hi-speed synch, VSS, Top View, Electric tow-bar, Heated steering, Storage, DAB, Heated electric seats, Moonroof, Adaptive High beam assist Xenons, Servotronic, Performance control, etc.