So I was poking around under the bonnet whilst bored at work and I noticed that the coolant in the tank(shown in red) was low but I filled it last week! I haven't noticed any kind of leak or anything under C and no puddles form when parked. Is there something else going on that I don't know about? Also, what is the one in yellow??

 

The yellow one is the power steering fluid. It doesn't look like you have a leaky coolant reservoir (a common problem) from the picture but it is a possibility. How low is the level? I don't want to presume without knowing more info.

 

I filled it to the indicator line, and when I checked it today it wasn't bone dry but I could see the bottom. And when I get home today I'll fill it again. Good thing I got the gallon jug

 

Hmmm. If it's not leaking out of the reservoir (you'll notice white powdery residue on the exhaust heatshield), then it has to be going somewhere else. I don't want to alarm you but one remote possibility is through a leak in the headgasket. The coolant would either leak into the cumbustion chamber or into the oil causing it to turn a milky color. There was an issue with early cars leaking at the water pump gasket. I had this issue but it left a puddle under the car while sitting overnight. You might want to take a trip to your MINI dealer and see if they can find anything. They can pressure test the system and go from there.

 

Well I just ran outside to check the heatshield and it was a little hard to tell because of the fading light, but to me it looked like there was white residue. If it is in fact leaking there, is there some kind of gasket in the hose or reservoir? Or would I replace the entire hose and or reservoir?

 

It's a well-known problem with the reservoir. If you do a search for leaking reservoir, I'm sure there will be loads of info. With white residue on/under the reservoir, that's most likely your problem. Take it to the dealer and tell them you think it's leaking. Mine's been replaced twice since '02.

 

Here's a pretty good thread on the issue.