I've had my mini for almost a year now, and have had a problem with the coolant system nearly from day one...to make a long story short, a friend who has a shop tested my coolant the other day and it indicated exhaust is making its way into the coolant system.

First thought was a head gasket failing, but I cant imagine a head gasket would fail for this long. Also, the oil has never shown signs of coolant mixing with it, the coolant itself is nice and clean, no moisture on the oil cap, no residue in the expansion tank, no coolant loss, and no white smoke in the exhaust. The car also drives just fine, still has a ton of power.

If not a head gasket problem, where else could I be pulling in exhaust from?

To expand on its issues: shortly after I got the car, I was driving it hard (not beating on it though), and it flashed the yellow temp light. I drove it home and found the expansion tank nearly empty. I refilled it and bled it (or so I thought) and it was fine at first, but within a couple days it would climb up to temp and once it got near 200F the temp would spike to near 240F and blow a bunch of coolant out the tank. I'd force the thermostat open and it would be fine for the rest of the drive. If i then shut the car off, then started it again a few minutes later, it would do it again.

I bled it countless times and it finally stopped doing it, but started doing something else. It now gets up to temp just fine, doesnt over heat, but if I dont force open the thermostat, it'll push coolant out the expansion tank after several miles of driving. If I open the thermostat after it hits 220F, everything works perfectly.

So, I'm at a loss, never seen anything like this. Going to try to get a compression test done before I have to make the 1000 mile trip back home, but beyond that, I dont know what to do short of bringing it to a dealer and letting them take my money.

Any thoughts?

Thanks.

 

Sounds like the shop's diagnosis is right. You can buy a test kit and do it yourself to verify. If you have combustion gas getting into the coolant there is no other spot but through a busted head gasket.

There's a slim possibility that it was a defective gasket, but man that's rare. Get a second opinion with the test kit. For assurance, do a leak down test too.