I have a 2003 mini cooper s
When the engine is idling and i remove the cap the coolant begins to be pumped in and out consistently and then begins overflowing and when i drive it it leaks coolant and over heats but cant tell where the leak is coming from
I need help please

 

Not sure I completely understand what's happening here, but why are you removing the cap with the engine idling? That's a sure way to cause your coolant to boil-over and engine to overheat. The coolant in the tank must be kept under pressure, hence the cap which is calibrated to hold about 16psi. If the cap is off, or isn't holding pressure, you will have boil overs and/or overheating.

The tanks themselves can leak at the horizontal center seam. The leak is usually detected due to dried coolant residue along the center seam. If that's the case, replace both the tank and the cap.