I'm sure the cosworth gasket is fine and that's not a bad price. Cosworth is a very reputable company and have been around a while. I've had nothing but good results just using a new OE gasket; even with a Cosworth head/cam installed. I don't know how thick the cosworth is compared to stock but it might be just a bit thicker because it is composite; but that's just speculation. I'll let you do the real in depth research, I get enough of that to do at work the way it is.

 

Not sure if this applies here, but I owned an MGB that would overheat when idling in traffic. Even tried a cooler thermostat (165 degree) with no luck. Come to find out that the 50/50 mix contains way too much antifreeze for the MGB. A local MG expert suggested going with a 25% antifreeze and 75% water mix; I did and the "B" never overheated again. This was in Denver so the mixture worked well in that altitude and cold temps.

May not be relevant, but I thought I would throw that out there.

 

It's a good tip, I've definitely seen instances like that before but the Mini cooling systems seem to flow well enough and cool efficiently enough that the mix doesn't affect running temp by a significant amount. That electric fan moves a ton of air, especially on high speed. I've always filled the Mini's (and other newer BMW's) 50/50 and never had a problem as long as everything else in the system is working as it should be.

 

you can find the freeze point vs mix ratio of antifreeze and water. Then you choose the mix that's appropriate to your local weather (with some headroom to be safe). More water works better because it takes more heat to change water temp by one degree than it does for anti freeze. This means that the more water you have, the more effective capacity your cooling system has.

Matt

 

kinda late here with this but you really ought to look into a head gasket kit as you will diturb alot of stuff getting the head off and alot of it should be regasketed . try mini mania .

 

 

i have been using autopartsplace.com they have the complete set shipped to Hi. for $220. it includes the head gasket. order 11 12 0 147 561 victor reinz. it will be a little less for people not on an island.

 

Quick update / resolution (I hope!) Got the head gasket replaced (along with oil, coolant, & spark plugs.) Opted not to do it myself -- I like tinkering, but that seemed like a bit of a stretch for a first job. Car's running the best it's run in quite a while.

 

I have what seems to be exactly the same problem. Bought my 2002 cpe from a friend; have known it since it was bought - close to mint condition until dealer rad and cooling system flush. Now, heater was ok until overheating started, then quit blowing hot. Coolant expanded and blew off the expansion tank cap, spewing anti-freeze all over the place. Any more ideas along these lines? I'm thinking trapped air but will listen to other opinions; especially from Hopingtokeepit! thanks up front-

 

The timing definitely sounds suspicious. How long after the coolant flush did it take before the car overheated? Was it on the way home, or a couple weeks later? (The former says "improper flushing" to me, the latter is what I had.) In my case, there was one time when I know it didn't get flushed right [different person did it] and it started overheating within a day, without much driving. The other times, it took a while. The coolant system is under pressure, so the only way air will go IN is if it's at a higher pressure -- i.e., via a leaking head gasket. (Anywhere else, and the fluid goes out instead of air going in.) In my case, it wasn't a big leak, so it took a while between flushes before the air would build up enough to cause a problem. People usually say to check for "milky" oil for a leaking head gasket, but in my case the oil still looked pristine.

The catch: even if this particular overheating was caused by improper flushing/filling, my understanding is the fact that it overheated enough to blow the cap means it may have also overheated enough for the head to warp (it's aluminum) -- leading to a leaking head gasket... I guess it might also be possible for the head gasket to be leaking badly enough for the pressure to blow the reservoir cap even without the coolant getting too hot, but from your description it sounds like it happened gradually? In any event, I'd take it back (if it's that bad, you might not want to drive it though), explain the (new) symptoms that showed up after they flushed the coolant system, and ask them to re-bleed it. That way, 1) if it's just a bubble, it should theoretically get fixed; and 2) if it was just a bubble that caused bigger problems, it'll be documented...

One other thought: since it's an '02, the PS fan is on the same circuit as the rad fan -- and the PS fans seem to die pretty easily. [Mine "coincidentally" died when the dealer was working on it.]

Good luck! Keep us posted on how it goes -- you have my heartfelt sympathies...