I've had a 2004 R53 since new. This is the first summer that the fan runs after the engine shuts off. Have never seen any change on temp. gauge, same temp. as usual. Is something about to fail. Just replaced plastic coolant tank with metal because it was leaking, second one. The plastic one lost enough to make me think that maybe the reason the fan was running. That doesn't seem to be the case as today under normal driving with the temp. gauge just under half the fan was running again after shut off. About 5 min. or so. Any thoughts, Thanks.

 

When the tank failed, its possible the system went low on coolant, and a bit of air got into the system...
Simple and free thing to do is bleed the system...see if it changes. Remember, there us TWO bleed valves... One by the top of the radiator. The other by the thermostat.

 

Thank you very much. I will do this.

 

This tech article here may be helpful when you go to bleed the system. It starts at the 9th paragraph from the bottom.