Have an 2009 Mini Cooper Clubman R55 base 6MT. Just pulled and overhauled the n12 motor, included in all the new parts is a new thermostat assembly and metal water pump instead of the plastic. Car will dangerously overheat at 236degrees and start to misfire bad in cylinder 1 before I have to turn off the car. Just realized I haven’t heard the radiator fan in a hot minute. So I went to unplug the coolant temperature sensor from the thermostat and the turned the car on after a couple minutes and Dan came alive!

With fan on and the heat on low the engine stays at 180-190 degrees and works fine. My a/c system is still empty and hasn’t been charged up since I put the motor back together back in, so my mechanic friend says that maybe there needs to be refrigerant in the system on the A/C pressure switch for the fan to work properly. I have no idea where to start looking to see what’s up with this fan not coming on when it should. Any ideas or similar problems happen to you guys?