The vehicle is 1984 380SE.
There is a vacuum line that is either leaking, or the terminal device attached is leaking.
It's color coded purple-grey, and located on the same check-valve as the headlight level adjustment line, at the firewall next to fuse box. It goes around the fuse box into the body, and don't where it's gone after that. Tried looking through the CD-ROM, but haven't found any clues so far.
Can someone tell me what it's for?