Does anyone have any ideas on how to tell if running hot is because of the thermostat or water pump. On my BMW 330 the thermostat usually fails open. My fan is working so that is not the problem. It would be nice if I had a good trobleshooting guide but have not been able to find one.

 

I took believe my car is running hot. Did you ever solve your issue?

 

I knew the car was running hot just wasn't sure what the problem was. The problem was the water pump was not turning because of the friction pulley that turns it.