I have just got my car back from the mechanic and noticed this loud slushing noise when i accelerate/brake hard and thought it was coming from the back door and just pulled the bung out to see if it was inside the door and the water came flooding out-about 4 or 5 litres of it. I have had alot of 5 series before and never had this issue before, or heard of it. The door seals dont appear to be wet and i can't understand where this could be coming from, but it is quite bad. Has anyone experienced this before? The mechanic installed a new regulator in this door so now i am thinking maybe he didnt put something back together right. I removed all the bungs from the others doors and there was no water in them. Im worried about this rusting the door. (Car is not a sunroof model.) Any help would be appreciated.