Been lurking here a while. Recently, purchased a 2012 R56 N18. The car over heats. I replaced thermostat (mini) and fan (oe). Still overheating. Fan comes on with scan tool, ac, and unplug temp sensor but does not come on when temp rises. Coolant begins to rise and sizzle out, coolant tank really hot. I did fill coolant with schwab coolant fill tool so should not have air in system. Looking for help suggestions here. Thank you.

 

You didn’t mention how many miles you have on it? You might want to check the friction wheel that drives the water pump from the crankshaft pulley. The spring loaded tensioner maybe worn out

 

57,000 miles

 

The friction wheel drives the fan? I thought the temp sensor in thermostat drives whether fan is on or off depending on temp?

 

No, this friction wheel drives the water pump from the crankshaft pulley

 

Water pump is turning. Fan is not turning on. I replaced fan. It worked for like a day then no more. Leaning towards battery now

 

Bled coolant more. Fans work. I am now experiencing misfires in cylinder 3&4 upon cold starts. Sometimes check engine. Sometimes not.