So, three days ago I was going to check on the condition of my air filter. Before I got to that, I noticed my coolant level was way too low (perhaps 10 mm up, from the bottom of the container). In other words, the coolant-level was way below minimum. I filled up the container with ready-mixed coolant until it was almost at max. Today, three days later, I found that the coolant level had sunk to almost the minimum mark.
Good news is, my oil has not turned grey. Therefore I'm assuming the top (I have no idea what the American word is; jam pack or something?!) is allright.
Bad news is, I'm guessing there is a leak.

What do you guys think?
Thanks.

 

cylinder head, I think was the term you were looking for...

Check the thermostat housing..

 

How exactly do I check this?
Where is it placed?

Thanks!

 

Do a search here. There is a how-to on replacing the thermostat. It is a common problem on R50 & R53 MINIs.

Here it is I found it for you..... https://www.northamericanmotoring.co...at-change.html

 

Check your reservoir tank, I was loosing fluid, actually seeing little puddles under the car and would smell antifreeze at startup. My reservoir was leaking at the seam, dripping on the heat shield then onto the exhaust.
Start the car and let it come up to temp, then look at the reervoir seams, once the coolant system comes up to to temp a leak will show up as antifreeze bubbling out of the seam if it is defective. A new tank is only ~$40 and takes about 10 minutes to replace. You can check around the thermostat if it isn't the reservoir, although MINI's are notorious for leaking reservoirs.

 

From what I remember it was R53 MINIs that had leaking coolant tanks. The OP has an R50, but that is good advise to check the tank. I had forgotten about those leaky tanks. Maybe that's because my R53 never developed one, but did have a leaking thermostat housing.

 

Thank you guys,
can I check the themostat/housing without dismanteling anything? Can anyone explain to me in words, or preferably pictures, where it's placed?
The leak does not seem to come from the tank.

 

look between the end of the cylinder head and the battery box. you should see coolant hoses running to the top of the block there and where they connect to the block is the thermostat. If you see liquid here it is probably your leak....altho you may only see residue of where the leaking coolant cooked off on the hot motor.

Removal is pretty straight forward but you may want to pull the battery and battery box first for better access.

 

Just wanted to mention that leaking thermostats are common on R50s. I had mine replaced in Feb. 2009 and was told at the time that it was a common issue. I'm guessing that the replacement part is no better because I just found out it is being replaced again about 1.5 years later. I decided to have it checked during my final warranty service visit and sure enough, they found that it was leaking again. I just told them on a whim that it might be leaking since I did not notice a significant leak (as I did the first time), but rather a slow decrease in coolant level over time. Glad I did!

Since the first leak, I've made a point of checking all fluids a little more regularly than most people do. I would suggest other R50 owners do the same.

 

I think I'm having the same issue with my GP. Noticed some dark bluish-grey fluid on the floor. I'm supposed to have it checked out at the dealer this Monday but I think I'll look into first myself (with the instructions you guys provided above).