My girlfriend 2003 Mini (non S) starting overheating today. All of sudden she noticed the hot air became cold, a few minutes later the temp guage dropped to nothing, and then went to red hot, coolant bottle was also bone dry when it was full last week.

Checked for leaks and can't see anything, ran the car in the garage for awhile and it wouldnt overheat again however air is still cold at operating Temp. I was thinking water pump or thermostat however coolant seems to be flowing as at operating Temp the upper rad hose was hot and the lower was warm.

Any ideas?

 

Thermostat may be bad? Check for liquid on top of the transmission case. There may be a blockage to the heater core since the air blows cold when it should be hot. The Cooper water pumps are massive for the size of the car and motor and do not fail often.