Same as mine
If its the piece I think you're describing, its identical to the drain on my S500 W140. Actually, I think there are two...
Anyway, looks to me like they drain off any accumulation of water that may make its way into the air intake system from outside.
Yes, only about 4 inches long with a 90 degree bend in it. Mounted in a hole on the front side of the air system.
Its pretty hard to get the air plenum into position without pinching these things against a brace; that, and some age probably causes them to break.
Not sure how "critical" they are, but the pinched end (lets water out, restricts air flow in) tells me the designer didn't want air coming in that way. Maybe it would bypass some of the recirc function of the climate control?
Why not replace them? Only a couple bucks a piece. 5 minute task.
Hope this helps, KenP