Might not be what you want to hear but on my 450SEL (W116), I completely abandoned the vacuum system. There were enough leaks and broken hoses that it would never have worked without all new components. I installed electric actuators in each door and the control module under the dash.

Was it original? No. Was it a pain to run wires all over the car? Yes, yes it was. Did it work every single time, in the cold, in the heat, after sitting for weeks? Yes it did.

Mine came from A1 Electric and wasn't cheap at $150 but it had "Swiss made" MES actuators and I was easily impressed.

Michael

__________________
Usta haves '69 250/8, '76 280C, 1971 250C 114.023, 1976 450SEL 116.033
Current have, 1983 300SD 126.120