Alright,

I think I have figured out the issue with the car not turning off with the key. I have replaced all of the vacuum fittings underneath the hood and temporarily disconnected and plugged the hose that goes to the yellow diaphragm and plugged the hose (this bypasses the source of the leak and allows the car to shut off.) I removed the panel underneath the driver knee area and can hear the vacuum leak. When I wiggle the solid yellow vacuum hose, the squeak of the leak changes pitch. This leads inside an area that I can't seem to get access.

Any thoughts or tips to help me figure out what to do next would be greatly appreciated.


Edit:


OK, I went to take some pics and found that it leads to what looks like a small dashpot or something similar. Can anyone get me the part number for this? Talk about a ROYAL PITA to access!!

OSB, sent you a PM to get Sam Ross's Vacuum diagram....

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1998 W202 C230 - The money pit of late.
1984 W126 300SD (356,800 miles) Gone to the wrenchapart
1984 W123 300D Gone to the wrenchapart
1972 W108 280SE 3.5 (sold but not forgotten)
1986 Buick Grand National 3.8l Turbo (86k miles)
1966 Glassic Model 'A' Replica http://www.glassicannex.org

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That yellow line is the vac supply line for the door lock system. Just to be sure that it is in the line, pull the door panel and find the solid yellow line again, and plug that end and use a MityVac to check to see if the line can hold vac.
In my car there is a vac check valve on that yellow line. I don't think you can get to it with out the dash out. I replaced mine when I had the dash out to replace the climate control accuators.

Check Valve - http://catalog.eautopartscatalog.com/mercedesshop/sophio/quote.jsp?clientid=catalog.mercedesshop&cookieid=1L00T87R01VU0UGVXW&baseurl=http://catalog.peachparts.com/&partner=mercedesshop&year=1982&product=O4040-32232&application=000023991

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