Now for the bad news. The saga has only started! As the acid leaked through the lines with vacuum in them pieces of disolving plastic and acid vapors got pulled through the vacuum system all the way to the source.
The hardest problem I have ever dealt with on one of these systems was only a couple months ago. A close friend who is shop foreman of a european dealer was working on his neighbors car and had replaced every vacuum element (all lines under battery had been replaced in the past). My assistant spent a morning on it before I pulled him. I spent a half hour tracing vacuum and found that the metal tube in the vacuum manifold on the servo was rusted totally shut. We drilled through it and thought we were done. Another four hours of various seemingly changing events and I told my assistant that I would come in on Sat and fix it. After getting thoroughly confused, I finally did the vacuum circuit tests as the manual directs ( I have fixed hundreds maybe more of these systems in 116,107, and 123 cars and never used the test steps.
On the second test (I think) I found that the other end of the same line had another metal section in the manifold that plugs to the pushbutton assy. It only took me 30 minutes to find it after the test.
The moral to this story is that the acid will follow the vacuum to the source. I have only done repairs to the disasters and I'm not sure what can be done except to blow through the proper source lines, especially at the servo and the pushbutton. I wouldn't blow through the servo though.
Bosch Master, ASE Master, L1
33 years MB technician