I have a 2008 Z4 which has been diagnosed with drain problems. I could hear sloshing water and the dealership discovered that my drain system was clogged w/ debris. The service manager told me that to get all of the stuff out of the drain I would have to have the top removed. Of course the warranty is not kicking in (outside influences). I did go to a top repair place and they disagreed about removing the top to clear the drains. If any of you have experienced this problem please share your solution.