Had this same problem on my 94 E320 wagon. (104.992 engine) The plug does come out, but it is made of aluminum and the threads will likely be trashed by the time you get the plug out. Be sure to use a 6 point socket or you will round off the part that sticks out of the block. Once I got mine out, I had to clean the leftover aluminum out of the threads in the side of the block. Had to get a new plug from the dealer.