300sd vacuum lines - disconnected line under dash
 

1983 300sd

While upside down under the dash to change the cruise control amp, I noticed an apparently disconnected vacuum line under the driver's side of the dash.

The line in question is a thin black line that comes through the firewall pretty much to the left of the cruise control amp. It comes through a grommet that also contains three much thicker vacuum lines - a red/green, a blue/brown and a brown. I cannot find anything that the thin line should have been connected to (i.e. the other end....)

I've also found a vacuum diagram on this forum that talks about a cabin vent line that is also black, that is connected to the vacuum control valve.

Have I found my cabin vent or have I found a line that should be connected to something else?

sounds like the vent line - but do you have any vac. related problems? Doors, fuel cap, trunk, etc?

Nothing like that. Everything seems to work OK. I have some climate problems from time to time but those lines are much thicker than this one.

The upshift from 1 to 2 gear is a little abrupt but I do not think that is connected to this line in the cabin.....

cdplayer
 

It's just a vent line. I freaked too while scoping my 300SD years ago. Shop CD confirmed "vent line". Your good to go.