I have a vacuum leak in my 85 300D. I have done a fair amount of "mitivac research" and determined that the green hose with a yellow stripe that comes through the firewall to the engine compartment will not hold a vacuum. Can someone tell me where it attaches inside the cab? From reviewing posts, I think it links into the HVAC system, but not sure.

If so, I have a couple of questions:

1. How difficult is it to trace the line into the cab? Will it require removing the dash? Will it require multiple test through a number of pods to find the leak (like is required for door lock related leaks)

2. If I just plug the line in the engine compartment with a golf tee, will the buttons that control my AC and Heater still function?

I really appreciate everyone that posts to this forum. If you were not here giving me repair tips, I'm sure I would not have continued to buy more and more Mercedes over the years. I believe I (my family) now owns 7 cars (two are parts cars).

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02 E320 Black (198K)
85 300D Blue (147K)
83 300D Blue (299K)
Plus 2 300D Parts Cars
05 ML350 Silver (165K)
02 ML320 White (207K)