One problem related to transmission fluid leaking has been reported for the 2005 Mini Cooper S. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Mini Cooper S based on all problems reported for the 2005 Cooper S.
In the early fall, September 2011, I encountered issues with my car not shifting properly. It's an automatic transmission so I know there was nothing I could be doing to cause this problem. The car has been serviced regularly and driven with care while in my possession(I'm the second owner. No similar issues on carfax report). While the engine is cool and not yet at its optimal temperature the drive is fine and you may not even notice a problem; however, every ride, once warmed up the car begins to shift incredibly violently as it is obviously struggling to switch gears. This occurs also while slowing down and the car is downshifting creating an opportunity to be "slung" into a car from behind(this happened in the mid summer of 2011). After dropping this car off September 15th to the local Mini dealership, I did not hear from them for almost three weeks. In the first week of October I was contacted and told it looks like my car is very easily fixable and should be ready shortly. It was explained to me that a seal had broken on the transmission leaking fluid onto it causing this shifting malfunction. When they finally told me I can pick up my car(approximately October 18th) they regretted to inform me the problem was not able to be fixed and I would have to bring it elsewhere as they do not rebuild transmissions. Now it is back in my possession where I am forced to commute in it daily, driving worse than it was before I dropped it off. It now displays "pe" for its current gear from time to time. This is not the only complaint I have filed for this car matching other consumer complaints. I am a victim of their failed power steering as well.