View Full Version : Overheating

09-11-2012, 06:24 PM
I have a 2007 BMW 750li. Love the car but am having overheating problems. The radiator fan doesn't seem to be running. Is it the fan itself or is it the thermostat or a relay or fuse?

Any help would be greatly appreciated.


09-12-2012, 02:23 AM
Start the best way flush the radiator and check your coolint reser. Cap had that problem and had to replace cap and a hose but also turn on your car take cap off then see if coolint moves level up or down if no level change it could by your water pump, good luck.

09-12-2012, 07:35 AM
Thanks. Checked the reserve cap and tank. levels where a little low so i topped them off. no leaks in hoses or cap. i will check the level fluctuation to see if water pump is working. but my problem i think is that the radiator fan is not coming on. going to try to replace the coolant temperature sensor.

09-12-2012, 07:45 AM
You radiator could be clogged by dust, dirt, and debris or the fins could also be damaged (which I doubt) but after flushing or even before flushing I would get a presure washer and spray the radiator itself to get dirt/debris from between the fins that may help. I work on Generators from time to time and that usually causes them to over heat.

09-12-2012, 08:39 AM
That shouldn't keep the radiator fan from coming on though. Checked radiator it is pretty clean of debris. car only has 39,000 miles.

09-12-2012, 08:39 AM
Well, radiator won't even start if second temp sensor shows low temp. And it's possible if you have an air bubble in the system, but 99,9% it's your wheep hole gasket is leaking back to valley pan.
Anyways check your lower hose, if it's cold don't even think about driving your ultimate machine! And this is the best advice btw, in my case they told me it was my head gasket;) but I fixed the wheep hole and it's running like a champ.
The temp should not be higher than 105C, and lower hose sensor shows 66-67C when fan kicks in. In other words lower hose sensor controls your fan. Also turn on ac, if fan is working it means your problem is not in the fan. Fan has very advanced schema inside it, usually it's bullet proof on these models.

09-12-2012, 09:21 AM
Ok to check your fan look at a sencer on your lower hose as u stand in front of your 7 a hose u can see on your right side that is your upper hose the left side has your lower hose right were it connects from the radiator that is your fan sencer disconnect it and it should keep your fan on at all times, that way u know if the sencer and your car are in contact with each other and it not your fan sencer try that