Well, the climate control main line from under the hood on my 84 300d definitely leaks fairly quickly when I apply a vacuum. This is odd to me because I have pulled the plastic/wood over the climate control controls and the switches above them and tested all 5 lines from the switchover valves.
None of the lines leak, the one notable exception being the air recirculation pod (switchover valve 4), which seems to leak until it is fully open (the vacuum line going to it is REALLY small and it opens and closes very slowly for lack of airflow). I can't explain this. Anyone know what's with that?
I blocked off the line to the recirculation flap to keep it from having any impact, and theres still a leak. Could this be the switchover valves?

As a side note, my recirculation pod and defrost halfway diaphragms were bad, and the lines going to them are clogged.