[mister37]

Had low coolant light come on & off when stopped on decline. Since it wasn't a permanent caution, I didn't fill it up for a while. 2 days ago It came on again so I went to the dealership grabbed a bottle of BMW coolant, bought distilled water and put around 2L of 50/50 mixture in the reservoir.

I think I might have overfilled it but I read few posts that say that there is fool proof mechanism and it will throw out excess coolant. Is it true ?

I live in midwest and temp are low here, lately it's been in single digits during the night and in teens during the day. I have noticed that the radiator fan goes nuts when you turn on the heat. It seems to get louder as you increase the fan speed of the AC inside. If you drive the car for 20/30 minutes without heater on the radiator fans doesn't seem to turn on. The oil temp goes up normally.

I never had the radiator fan go berserk before so I was confused. I made a video if you want to look at it.Radiator Fan Full Speed

Please help me out here to understand what's going on, I did some searching but I couldn't anything that would make sense to me.

[tlow98]

Your water pump or thermostat or both have failed. They need to be replaced.

For peace of mind, get the codes read to make sure this is the issue.

[F22_Raptor]

Yep, bad thermostat = constant loud fan
Your car needs a new tstat along with a new water pump and a coolant flush.
I had the exact same problem, but changing the tstat and wp fixed it.

[mister37]

Alright so I did a water pump test .... like you do when you flush the coolant. It works it was pumping out coolant for about 15-20 minutes. I think my thermostat might be bad.

Is it okay to drive the car short distances 5-7 miles like this for 2-3 days? I can try to drive it without turning on the heat.