What is this thing????
 

This gadjet is mounted on the drivers-side inner fender on my 1985 300D. Note that on the left leg of the vacuum line "Y" has nothing attached. There isn't a vacuum line laying around that would have fallen off of it. Does there need to be a line on it, and if so, where would it go to?? Any help would be appreciated. My old Haynes manual devotes exactly one short paragraph to the vacuum system. I guess they were afraid to get into it.....Thanks...Dave

Never seen anything like that on an MB before. Is it a US model or from another country?

Pressure converter for the EGR.

FSM section 14 says "positive vent line" for both of those. The diagram shows it connecting to a "Y" joining up with a line from Switchover Valve. These two lines join up, then go into a "vent filter" right near the VCV.

Look near the VCV near the same place where the vent line to the passenger compartment feeds off. That's about where the Y/filter join in..

It's a US model as far as I can tell....

OK.....What's the VCV????

Can't you understand gibberish?

The vacuum control valve = VCV. The shutoff valve towards the back of the IP. Near the oil filter housing, underneath the green dashpot/damper doo-bob, whatchamahooser.

Answer
 

http://www.peachparts.com/shopforum/diesel-discussion/267879-unobtainium-mb-diesel-parts-list.html

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I believe it's a vacuum converter, on 85's only.
http://www.peachparts.com/shopforum/diesel-discussion/304788-new-84-300d.html

The link has an attachment showing how to by-pass the egr system on 85's.