My '08 Mini Hatch (non-S) lives outside most of the time, but brought it in the garage last night to use it for a few days checking it out for winter. Quick check last night of the fluids found everything cool - except the coolant was about a half inch below the "full when cold" line. So I added some coolant to that line, and actually added enough to get it to the seam that's halfway up the overflow tank (where it looks like the tank got seamed together. Woke up in the morning and found just about all I'd put into the overflow was all over the ground, and the dripping was just behind the bumper through the lower plastic shields. Quick search inside the engine bay found zero leaks around the overflow tank or any of the hoses.

Drove the car about 10 miles this morning, checked it and the system was holding pressure well - no leaks. Let it sit about 3 hours and checked it. Cooled down, level in overflow is what it was before I did anything last night, and no more leaks.

OK - this is my first Mini/BMW. I've always been able to add just a bit above the "full cold" line with no issues. IN looking at what I added it wouldn't make sense that I'd hit any level that could cause a siphon - but with all the baffles inside the overflow who knows what's deep inside. Was what happened just the system self-leveling itself? It could be that the coolant drained out the overflow hose, since it appears to go somewhere between the front bumper/grille and the engine compartment.

So before I go and have it checked - was this just normal behavor for a Mini overflow tank of you add a bit too much - even just a little bit?

thanks - andy

 

There's no overflow tube that vents excess coolant.

If you put coolant in the car and it leaked out you have a leak somewhere, or the cap wasn't tightened all the way.

Get the car up to operating temperature, shut it off, and crack the bleed screw on the thermostat and see if you get air out.

I might also recommend having the system pressure bled.

 

My car is an 08, and I had a cracked overflow tank. Remove the tank and look for any cracks or evidence of leaking (blue/green streaks or residue). Just take the screw off that holds it to the radiator support and look all over the tank for anything that doesn't look right. Do it when the car is cold, because if there is a leak it will potentially burn you when hot.

If you have not changed the thermostat or anything on the coolant system (water pump, changed coolant), then I wouldn't think that you would need to bleed it. If you do bleed it, you should do it when the engine is running and up to temp.

Did you see an approximate location of where the leak was from? In front of the engine, left or right side of engine, or somewhere else?

Mike

 

Thanks for the replies. I checked the overflow tank very carefully, and it's dry as a bone everywhere, including the hose/clamp locations. And after the initial overflow in the garage right after I filled it, the fluid level sat at the lower arrow and has stayed there after driving a couple hundred miles. Not a single drip or leak since - when hot the pressure good - hoses nice and warm and not spongy, tank solid and not leaking.

I understand that it's a sealed system - but SOMETHING let the fluid I put in drain out - and not a drop more. The location of the "drainout" was just behind the front bumper, almost directly below the reservoir . If I didn't know better, it just looks like it drained/siphoned out what I put in - as if there were a drain tube like on most every other car I've had. That's why I've driven it a lot over the past couple of days (normally it sits outside for multiple days at a time). Highway, back roads, heat off and on - level is stable, not a drop.

I'll keep an eye on it to see if it changes over the upcoming week. The car has an extended warranty with deductible - so if it's the radiator or the tank it's covered - but not hoses. So fingers crossed. I don't have specific history on when the coolant was last changed, but what's in there is clean (and why cycles in after each run), and the rest of the car was obviously maintained, so I don't think I have any bleeding or internal corrosion issues in the system.

thanks for your insights.

andy

 

Just to close on this. Yesterday I pulled the mini into the garage after changing the battery. The car wasn't warm - it was stone cold. An hour later it had dumped about another cup of coolant on the garage - area from the bottom radiator hose. Overflow tank wasn't touched and level was stable. Brought it to the dealer last night and they reported back this morning that the radiator was shot. It was odd because, when warm, it was holding pressure - but when COLD it would allow fluid to leak. Who knows. Anyway, I was glad I'd bought the extended warranty on the car when I bought it. So I paid my $200 deductible for a repair that would have cost (via the dealer) $860 for the whole job.

andy

 

This is why I'm a firm believer in extended warranties. Weird **** happens just because sometimes. Glad you didn't have to cover the whole cost and that they found the problem!

 

Weird, but possible. It's not likely it is a typical "hole" in the radiator, but more likely a seal. O rings are forced at bit to move if the pressure force changes from internal to zero or external.

 

I'm not familiar with the construction of the Mini radiators - but if they combine any plastic with metal in construction, that introduces places where the different expansion characteristics can result in this. Will ask the service guys when I pick it up where the leak was at......