Vacuum locking System- Vacuum Front Driver door 83 240D

[Carrameow]

83 240D In fact in the engine compartment there is a plastic yellow distribution valve which takes one vacuum line and transfers it to the 4 or 5 lines that go in to the car. I see vacuum before it, but not after.
Also at the rear vacuum tank, I cannot draw a vacuum at the yellow intake line. There may be a unsealed sytem elsewhere.
Finally the front driver door cant lock except by key when you are outside car.(You cant push the button down manually)
I know, its just an 83 240D but I want it to bethe best one.
Is the yellow thing a problem component?