Hey guys!

So I changed out a bad thermostat housing in my wife’s 2013 Cooper All4 S making sure to label and mark all sensors prior to removing them. So I did manage to learn some new swear words while working on her cooper lol! Anyways got everything back together and the car ran fantastic for 8-10 days no problems! Friday my wife calls me at work to inform me the car is overheating bad 🤬 pulled things apart looked at the thermostat temperature sensor and it seemed fine but of course it’s new. Put everything back together once again, and to my surprise the engine is still overheating but now for Some reason decided to run rough and miss, almost dies at idle and I didn’t do anything different or change anything. I’m hoping that someone has either gone through this and can talk me through the fix, or if nothing else anyone of you may have some advice, suggestions idk as my title says, I’m at wits end and have no ideas what to do. Thank you in advance

 

Overheating -- assuming it is real that engine gets hot and with the fan running -- at some high speed -- the temperature continues to climb -- with misfires suggests a head gasket (or cracked head) problem. An infrared thermometer is nice to have because one can measure temperature at various places in the cooling system. Among other things one can confirm the hot coolant is flowing as it should.

In this case a relatively sensible DIY step would be to pull the plugs and check every one for signs of coolant exposure. One sign is the plug tip of the plug in the cylinder affected by the presence of coolant will be quite clean compared to the other plug tips.

You can drain the oil and catch a suitable sample and have it analyzed. Among other things it will be checked for the presence of anti-freeze compounds. There should not be any. At the coolant tank to check for the presence of combustion gases in the coolant one can use test strips made for this.