2009 Mini Cooper base. 127k miles. Thermostat and housing were replaced at 119k miles.

Recently the car has begun leaking coolant after shutdown. It doesn't do it while running, but after shutdown and sitting for a few minutes a slow drip will develop, leaving a decent sized wet spot on the ground by morning.

It appears to be coming from the area at the end of the headers, somewhere near the oil filter housing. Space is tight there tough, so it's really difficult to trace it precisely. The thermostat area looks dry as do the lines connected to it.

Oddly, the shop that checked out the car when I had the massive oil leak pressure tested the cooling system and found no leaks, so I'm at a bit of a loss to explain it.

Size and location of the overnight leak.


Some views under the hood.



I have a theory, but I want to hear what you guys think it might be first. Thanks.