850 GLT fan not working

[tito64]

i had the same problem, this is the procedure i followed first check how old is your coolant use the original same as BMW napa has it and remember to use distilled water , I used a radiator flush to remove all the residues and scales (bought mine used with 160,000 and had the yellow one , next is your thermostat, make sure is not closed mine was due to scaling must liklely) next is your coolant temp sensor did you check it at different temps the fact that is sending a signal to your computer does not means that is the right one if it loosing sensitivity the fan is going to run at odd times or is going to be stuck or not run at all when the temp is reached for the fan to kick in ,check with your voltmeter and before your boling point has to be sending almost 5 volts,if you have to replace it try to get OEM is about 65 DLLS but you will have peace of mind, apparently your fan relay is ok , and at last is your water pump you will find all instructions here get a new timing belt if you replace the pump. hope that helps

[tito64]

one more thing make sure the terminals for the coolant temp sensor are not dirty some people had that problem before