I know the thermostat does function, car will be at its typical 220F untill I hit the max A/C button and it'll drop to the 170s.

However, if I drive without the max A/C on, the coolant level slowly rises till it vents out of the coolant overflow tank cap. I know coolant will expand as it heats up, but there's got to be something else going on for it to overflow. I thought maybe the coolant level was just too high, but if I keep driving and turn the max A/C on, the coolant level will drop to the low level line.

I know I have an air bubble trapped somewhere, despite my MANY efforts to bleed it...if I'm sitting at a stop light for a minute or so, then rev the engine, I can hear the gurgling of coolant behind the dash in the heater core. This is all after a long history of the car over heating after I shut the engine off for a few minutes, then started driving again - the temp will just keep climbing and the thermostat wouldnt open in time and I'd have to coast or shut the engine down before the high temp warning flashes.

I'm at a bit of a loss at this point. There's no signs at all of a cracked head or anything, and if coolant is leaking or air is getting in, I cant find where. I dont want to buy a thermostat if I dont need to, but I dont know what else to try. Any thoughts?

Thanks,
Nick

 

Maybe a vacuum bleed will work. Other posters have discussed the difficulty to bleed our MINI's. I haven't run into any problems in bleeding mine after a coolant change and a thermostat replacement.

 

Yeah I've tried every which way to bleed it, to no avail.

I'd hope a proper coolant flush (at the dealers with a vacuum system) would help, but I dont want to shell out 100 bucks only to find it didnt fix it, and then spend another 100+ on a thermostat, only to have to spend yet another 100 to do another coolant flush.

I'm starting to wonder if the radiator is plugged up, I just cant understand why the coolant would be expanding to the point of boiling over, despite the coolant temp staying at its normal 220 or lower.