coolant temp gauge pegged hot

**newbie740i** · 01-03-2016, 05:57 PM

Hi All. Need help. have 2001 740i and the coolant temp gauge reads full hot when cold! checked obc with engine off and it is reading 46c. when i check obc with engine running it reads -168c Tried replacing thermostat and also replaced temp sensor. Please help me! I am at my wits end.

**ptarditi** · 01-04-2016, 07:08 AM

Try deleting the fault code, on certain models if the DME thinks the engine overheated it won't read normally until the fault is cleared. Otherwise I would check the wiring from the sensor.

**newbie740i** · 01-04-2016, 11:22 AM

Originally Posted by ptarditi

Try deleting the fault code, on certain models if the DME thinks the engine overheated it won't read normally until the fault is cleared. Otherwise I would check the wiring from the sensor.

Thanks for the advice. I discharged the electrical and now the temp gauge is full cold and not full hot. So now everything seems to be as it should. Thank you again for the help.

**newbie740i** · 01-20-2016, 10:56 PM

does anyone have a coolant circuit diagram? I can't seem to get a sensible answer regarding the thermostat. On the E38, is the thermostat controled by the water temp or does it have an element that regulates the open position. No matter how hard i look, NO one can answer this simple question.......Please help me.

**RyansBMW** · 01-21-2016, 07:37 AM

I can tell you the E39 thermostat is regulated by the DME. I would venture a guess the E38 is the same way

**newbie740i** · 01-26-2016, 07:44 AM

The problem that i am having is that it seems to be running too hot. I have replaced the expansion tank, water pump and thermostat. I know that the thermostat opens at 103c. That seems a little hot to me but i'm sure it has to do with emissions. My auxilliary fan only seems to come on when the a/c is turned on to max. At which time it will cycle between hi and low speeds. Is there a sensor that i have overlooked and if so where is it.