With the top cover removed, did you see a brass fitting in with a large slot in the top? On my 280C, you use a giant flat tip screwdriver to remove it for cleaning.
And BTW you need to remove it to get the cam box off.
The vent and line that I was talking about was in addition to this one.
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe