[Poloautoclub]

2011 335d cooling fan will not turn on. brand new relay, new fan, everything is getting power as it should. Car overheats with no warning? I have a scan gauge hooked up so it tell me the engine temp. Starts dumping coolant at 210F when idling. Engine temp stays around 181F when driving even under load or hard driving in hot outside temps. Anyone can lead me in the right direction?

[Hoooper]

Starts dumping coolant at 210F? Thats way too low to be boiling over. Where is it boiling over from? The pressure bottle?

[BB_cuda]

What coolant temp should fan activate at?

[fsd350]

The DDE uses several parameters including temperature, A/C system operation, ambient temperature to determine the proper fan speed and operation. i have had my fan runing and not running at 100c (212f) and below. 210 is way to low for coolant to boil. You may have a cracked reservoir which is fairly common on a BMW and/or insufficient coolant concentration. The boiling point of 50/50 coolant and water is 262f. Check the pressure cap also. Hope that helps

[Hoooper]

That's a good question. Mine only seems to run if the coolant temp is around 95c and up. It also runs most of the time when going slow and a/c is on.

[BB_cuda]

When on way home from cross country trip, I got caught in traffic jamb just west of Baton Rouge. I enabled temp display on cluster using the hidden menus on saw 90C on the display and engine fan wasn't running (A/C was off). I turned on heater first to dump heat without loading the engine and pulled display down to 84C. Curious if temp would increase again, I switched from heater back to A/C on and instantly heard the engine fan come on. Temps then pulled down to 79-80C.

If i hadn't done anything with the heater or A/C, I was curious how much hotter the coolant temp would have needed to get to activate the fan. Since serious Texas summer is now over, I'm not in position to try to make fan kick on without intervention. To be clear, when i turned on heater, the engine fan didn't come on. The cabin fan was rejecting the coolant's heat through heater core into cabin and i had windows down to not be baked.

[Hoooper]

Why turn the heat on and bake yourself when it's only 90c? No reason to get concerned until its quite a bit higher than that, like 120c. 90 is actually just about where it is supposed to run all the time.

[BB_cuda]

Originally Posted by Hoooper

Why turn the heat on and bake yourself when it's only 90c? No reason to get concerned until its quite a bit higher than that, like 120c. 90 is actually just about where it is supposed to run all the time.

Only did it for about 5 minutes just to see if it helped. I'd always heard to do this and this was 1st time i ever tried it with true data read out. It came down pretty damn quick. Agree 90C isn't a problem point but i guess it was higher than my normally observed 82C. I saw where you told me that 88C is more the norm for coolant temp but this was after my trip. Thanks Hoop!

[Poloautoclub]

its coming from near the expansion bottle.. My AC compressor was also not kicking in and the belt would start squealing really loud. So temporarily in disconnected the compressor. not sure if that has to do with anything? BMW is sending me a new fan and i will have in tomorrow (friday). i had the fan tested and when we tried to activate it the fan would twitch/ hesitate to turn on so now i am waiting for the new fan to come in. I will get back tomorrow with new and good results hopefully...

[Poloautoclub]

Ok so the problem has been fixed! The wrong drain plug has been installed on the radiator causing the coolant to come out before the fan had the chance to kick in. when you get a new radiator for this car it comes with two drain plugs... a short one and a long one. I had the short one in which caused the problem. Im so happy this is fixed! Thank you guys for the assistance