Head gasket failures like you're describing on your M104 engine are rare. More common on M103 engines.

See this link for a nice write-up by 71Rcode:

http://www.peachparts.com/shopforum/showthread.php?t=147315&highlight=head+gasket

__________________
Paul S.

2001 E430, Bourdeaux Red, Oyster interior.
79,200 miles.

1973 280SE 4.5, 170,000 miles. 568 Signal Red, Black MB Tex. "The Red Baron".