So my wife's 2005 X3 keeps overheating from time to time. I have checked the coolant level and even replaced the coolant (yes with BMW coolant 50/50) and bled the system. There are no leaks anywhere. I have changed the thermostat, all the hoses and even the coolant temp sensor. What I have noticed is that when I start the car, sometimes the fan never kicks in and the guage eventually starts to tilt right. I have also replaced the fan with a known good used fan but the problem still persists. Could it be the F AUC Sensor? PLS HELP!!!