I have had a vacuum leak in my 84 300d that prevented the door locks from working, and the engine from stopping. I plugged the line going to the driver's side door, which allowed the engine to stop when I turned the key off. Finally got around to finding the leak. Replace the master vacuum switch in the driver's door and still had a leak. Using the mitvac, I isolated the leak in the yellow line with the green stripe between the vacuum switch and where the line connects to the 4-way connector near the firewall. Question 1: What locks does this line go to? Question 2: How do I replace this line? Is there another way to replace this line?

Thanks!

I'm having trouble understanding which line you're talking about. From the connector at the firewall under the hood, there should be a solid yellow line going to the master switch in the drivers door, and then from that switch, there should be two lines (yellow/green stripe and yellow/red stripe).

On mine, the yellow line with the green stripe (and the one with the red stripe) come out of the drivers door and turn towards the back of the car, and there's a connector under the drivers floor mat. From there, it branches to the passenger side door and to the rear drivers side door.

If yours is similar, your unlock line (green stripe) will probably branch from the 4-way connector to all the other doors, trunk, etc. You'll have to pull the other lines at that connector and use the mityvac to test them. Its probably one of the vacuum elements in one of the doors. They have rubber boots on the upper side (unlock side of the diaphragm) that can tear or deteriorate, and that's where the leak happens. So you need to do some more testing.

Here's a good vacuum diagnostic thread:
http://www.schumanautomotive.com/forums/showthread.php?t=2755
It starts with testing the main vacuum stuff under the hood, you can probably skip down to the door lock part.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now