I just bought a 1979 240D, and have a question about the door locks. I've been reading on the forum, many threads, but can't really understand, I guess? Are my door locks controlled by vacuum? IF this is correct, if I lock the drivers side door, with the key, are all the other doors supposed to lock? If this is correct, how long after the motor is shut off, does this still work? I havent tried locking my drivers door with the key, but I know, with all the doors unlocked. When I shut the motor off and leave, when I come back the passenger side door is locked, so I assume this is some type of vacuum problem. If so, where do I look for the culprit, and how do I go about fixing it?
thanks,
Jim

Anybody have any comment on my questions?

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1979 Mercedes 240D (Sold to a neighbor last year,now I have room for a new one,looking for a 300D this time)
1980 Mercedes 240D(bought for a parts car, but I have fun driving it!)

if I lock the drivers side door, with the key, are all the other doors supposed to lock?

yep

If this is correct, how long after the motor is shut off, does this still work?

based on how bad the leaks are

I havent tried locking my drivers door with the key, but I know, with all the doors unlocked. When I shut the motor off and leave, when I come back the passenger side door is locked, so I assume this is some type of vacuum problem.

yep - an indication of improper operation

If so, where do I look for the culprit, and how do I go about fixing it?

start with the yellow plastic vacuum lines in close proximity to the brake master cylinder

take your time and good luck

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Jim

That is correct. It should continue to work for several days or lock cycles...which ever comes first.

If yours is not working buy an mity-vac and get testing.

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine