So I am in the middle of solving water ingress issues and have cleaned all the drains, and checked glass seals, and I believe that I found the cause on the foam tube for the ac evap drain. After repairing that, I noticed oil dripping from my ignition as well so ordered the new shutoff valve. I removed the instrument panel for easier access and all looked good, including the oil line and gauge are not leaking. The speedometer cable was a beotch to get back on due to big hands and tight quarters.

So, while I am waiting on parts, I noticed the black vacuum line not attached near the firewall and steering linkage. Did I knock this off from somewhere? It isnt very long and I dont see any spots where it ends to hook it back up.
Pics of the other side in the engine bay to show both ends. It is the all black line coming out of a three way splitter heading towards the firewall.

Attachment 124289

At this time, I am just concerned with this vacuum line and where it hooks up?

Thanks, 1981 300d non turbo automatic

Attached Thumbnails

   

Looks like the vent line attached to the Vacuum Control Valve...it's meant to dead end inside the firewall just as it is.

And as for attaching the speedo...my bleeding knuckles sympathize with you !

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1985 300D 172,110mi and goin' strong

Thank you, I was looking for the thread and just found it. It is indeed a vent line...Whew!
W123 Vacuum InterLock Diagram
One less thing to fix. for now..

Couple random points:

- The vacuum lines are color coded for function. Black = vent. The vent is to admit air to break the vacuum when the system decides there needs to be less vacuum to do the function intended. On the 123/124/126/201 the vent just terminates in the cabin (to suck cleaner and drier air than what is under the hood). On the 210 and newer, the vents terminate under the hood, but the lines have little filters on them, looks like a lawn mower fuel filter except the body is perforated.

- Be sure when swapping the shutoff you get the hook placed on the rack correctly. If not you can jam the rack to full fuel and then when you crank it you will race to max rpm. Best to have a piece of wood at the ready to slap over the air intake for the first crank, air starvation is the only way you'll kill it before it self destructs.

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The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech