I have been troubleshooting the central locking system on my 1983 300D. I have narrowed down the vacuum leaks to the rear door vacuum elements. I have tested the lines, and they are fine - the leak is definitely in the element. The lock circuit is good, and works fine, but there are leaks in both left and right rear unlock circuit. Does this sound right? It just seemed odd to me that the lock function could work when the unlock function leaked. I have tried securing the rubber fasteners to the vacuum line with zip ties but but that has not worked. I thought I would ask before shelling out $65 on new vacuum elements. Finally - if I find some of these at a junkyard - is it enough to just verify that both circuits hold vacuum? Any other tips to make sure that if I find them they work when I get home? Thanks in advance for any help.