1981 380sl 107 power door locks

[dima4855]

Greetings,
Got a 1981 Mercedes with a vacuum actuated power door locks that leak vacuum like crazy. I put a gauge on at the firewall on the yellow line and could not get it to hold any vacuum. The door locks work fine with the car running, however when you shut it off they don't work (or work but very briefly), is there a particular place where I should start looking for leaks?
Is it worth it?

Thanks in advance.