Dusty,

I think you're looking at a schematic of the five cylinder system. Every four that I've seen, simply has a tube from the valve cover down to a connection at the intake manifold.

However, you said that you saw a checkvalve at the crankcase. My daughter's five cylinder has the tube, and I was not aware of the check valve, this gives me something to check (no pun intended).

Good luck,

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Larry Bible
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
Over 800,000 miles in
Mercedes automobiles