I have a '77 240D which I purchased new and have kept well maintained. I have occasional problems with the vacuum door lock operators. Once I identified the problem the last time, I was able to repair and maintain the faulty operator. Now the problem has surfaced again. What I would like to know is there a way to determine which operator is leaking vacuum without taking the inside door trim off and removing the unit (s)?

I would greatly appreciate any assistance.

Thanks,
Walt

I had the same problem with my 83 300D. I had to remove the line at each operator with a electric vacum pump supplying a constant vacum to locate the faulty operator. It turned out o be the trunk lid lock operator. you need a vacum pump that will shut off when it reaches full vacum. It was time consuming. I used a vacum pump off of a ford f800 with a cummins diesel, it works off of twelve volts and has a internal switch that shuts it off at a preset vacum level. It also has a internal check valve.Kinda crude but it worked well and was cheap, I had one laying in my tool box. Just made the jumper wires. then I tied into the vacum line for the central locks under the hood.You need to block the vacum lines of individually until the system will hold vacum. There may be a better way but I can't see one.Just my expieriance.

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Keith Schuster
83 300D
auto\hydraulic mechanic 20 yrs

You can buy a low end vaccuum pump at any food auto parts store. Most come with a variety of fittings and plugs.

You can access the different lines by removing the carpeting. You can then test each line to find the culprit.

Idea - replace all the door units, the trunk, and the gas door at once and be done with it for ten years!

Chuck