Noticed a puddle of liquid where our 2010 MCS had been parked outside. Popped the hood and saw the coolant expansion tank was empty. Fortunately, we hadn't driven longer than 5 minute errands in the last couple days, so the car didn't overheat.

I have to run to work now and don't have a chance to look under the car, but what would the most common failures be in the cooling system? Any hints as far a tracking this down?

 

From experience on our '10 MCS hardtop, It could be a thermostat housing - another known Mini weakpoint. We were almost at 50k when it went bad.

I would bet that if you add coolant, you will have to add more coolant than would just fill the expansion tank to the high mark - it will go down into the hoses, too. It might stay at the high mark, and then the first time you drive it and come back, it will be empty again. Our initial puddle was more towards the center of the car.

My understanding is that you'd have to get under the car to see if that is the culprit. If you are adding coolant in the meantime, make sure it is Mini-approved.

Slim chance it could be the connections on the expansion tank. Not sure what the signs of a bad waterpump are.

So frustrating that these cars do not have a low coolant or coolant temp indicator.

Keep us updated!

 

Thanks. Do you know if the thermostat housing is difficult to get at. I DIY as much as I can, but sometimes getting at things are what stymies me.

 

I'm sure someone else will chime in, or there is a 'how to' on the forum somewhere. I like the idea of doing my own work but ours goes to the dealer in Allentown.

We've had good experiences there, and luckily, the thermostat housing was the only thing that needed repaired in the 2 and a half years we've had it. It also had some extended maintenance remaining so we were able to take advantage of that. It had a lot of work done under warranty and recalls before we purchased it at 32k as the second owner. Though at this point, it has an external rear hatch release that only works with the remote, and there is something loose in the driver-side door when the window is not up the whole way.

This might give you an idea of what you're looking at if the housing is the issue and you want to tackle it. So tight in those engine compartments!

 

The only spot I can see any pooling of fluid seems to be on top of the transmission. I'll start the car next and see if any more is visible.

 

That spot is right under the thermostat. I ran the car for about 15 minutes at idle (the car is still on jack-stands), so I don't know if I ran it long enough for the thermostat to engage. Any tricks to getting the thermostat to function while the car is on stands?

 

Have it run longer or take it around the block if you can...? Idling takes a while to bring it up to temp. Put it in Sport mode, too - You'd know it's up to temp when the car starts pop 'n burbling.

In addition, look around for dried spots, like water spots but more opaque. They'll stem from the source of the leak.

 

Thanks, General. I've got the thermostat housing out now and there is a dried 'trickle' along its edge. It looks like a seam in the plastic separated. Its replacement is on order and should arrive in a few days.

 

ah hah!
Glad to hear you found it.

 

Yep, leaks down on the transmission, mine did this a little and would seal back up after it cooled down and then leak a tiny bit when warm. Here is the DIY.

https://www.northamericanmotoring.co...hermostat.html