Does anyone have a copy of the vacuum diagrams for 83 300TD and the 86 300SDL ?

Specifically, my W123 has just started to "Not shut down". I suspect an open vac source as the central locking system started to have issue the day before.

I looked under the hood and do not see any disconnected lines, I found a black hard line through the firewall connected to nothing. Am I to believe that is intended to go to open air? Makes no sense.

Thanks for the help.

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85 300D 3 pedal. Current project.
83 300TD (need rear wiper assembly dead or alive)
84 300SD Daily driver
85 300TD almost 400k miles and driven daily.
98 E300D *sold
86 300SDL *sold and made flawless 10 hour journey to new home.