I have a 1995 C280 with 97K miles. During the past several days, in the morning when I go out to start my car and back out of my drive, my brake pedal goes almost to the floor. As soon as I pump the pedal 1 or 2 times the pedal returns to its normal position, and I have no further problems with the brakes. I took the car to my brakeman and he inspected all the hoses and saw no leaks plus drove it to check for a master cylinder leak. He doesn't think its a master cylinder at this point and said to wait a little to see if a leak develops before jumping to conclusions. He said it could possibly be in the anti-lock system? Someone else suggested a vacuum problem? I don't want to change the master cylinder if its unnecessary. Anybody have any ideas what the problem could be??