My 2002 Mini base model has been overheating. now to be specific, it only heats up when stopped at traffic lights and it takes a few of them to get it hot. I can cool it down by just driving it it goes back to normal. I know my low-speed fan does not work it hasn't since I purchased it a year ago. It never gave me much trouble other than I couldn't let it idle for more than 10 or so minutes at a time which I rarely ever did. I have never let it overheat...period. Okay a week ago I notice this problem that it started to overheat a little when at traffic lights and I notice the overflow is gurgling and spilling out a bit. And when I pull out the air cools it and it immediately drops down to normal temp. It seems I have to bleed it alot like it's getting air in the system some how.

Here is what I have changed this past few weeks: Water-pump, Thermostat & housing/radiator cap, coolant fan assembly and It still overheating. The fans are coming on properly now too so I'm confused. On a separate note every once in a while when I crank it its like it does not get a proper setting and it misses so i cut it off and re-crank and everything’s fine weird right? and it throws a code of misfire cylinder 4 when it does happen not sure if the two problems are related some guy said it might be blown head gasket but the mini runs great other than that I have no power loss, no white smoke, no coolant in oil or anything.

So that’s it, I am stumped do you think it might be an airlock maybe I gotta get it vacuum bleed or do you think it might be a blown head gasket? Or do you think it might have a leak somewhere? BTW I have performed a coolant pressure test and it showed it was losing a bit of pressure but I didn’t check for leaks as I had no idea then how to use it like i do now.

What is my next move? Thanks in advance and I will keep all updated in-case other members have this problem.

 

I'm sure someone with more experience will chime in but here is my .02:
1 - Did you replace the overflow tank? I believe the earlier cars had issues with the tank which could also be the leak? If the tank goes dry then air can be introduced into the system causing over heating, even if you refill the tank (unless you re-bleed)
2 - New does not always mean works, so maybe you got a bad thermostat
3 - Misfire on cyl 4 and overheating plus pressure leak does seem to point to the head gasket as I believe the introduction of coolant can prevent a cyl firing... getting it started probably burns off the coolant allowing for the engine to smooth out (although I don't know why stopping the car and restarting it helps)

Someone with more knowledge can probably tell you what to look for on the #4 plug (color wise). You may want to check for smoke at the time of the misfire, if it can be predicted.

Good luck

 

I would pressurize your cooling system. See if you notice any pressure drop. Even though you say you haven't overheated your car you did run it warmer then normal. Over a year of doing that you could easily have a head gasket that's slowing leaking air into your cooling system. Its possible it could be coming from number 4 cylinder if that is the one that is misfiring.. But also remember those two issues might not be related either. You just might have a lot of air trapped in the system. So you could just keep bleeding it. You may also do a compression test. see what you get across all your cylinders. That alone will tell you a lot. Good luck!

 

I have not replaced the overflow tank. I will check for leaks on it. My next move will be a combustion gas test to see if hg is blown then if not compression test. If both negative then i guess vacuum bleed it?? I checked spark plugs and the cylinder 4 plug smells different from rest and has a olive color to tip. My antifteeze is orange so not sure but it does smell weird maybe there are small amount of oil mixed in with it but none in oil.