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Old 04-15-1999, 09:22 AM
Moses McKnight
Posts: n/a
Hi, I'm having some problems with the vaccum system in my 81' 300D. How can I tell for sure if the vaccum pump is bad or not? When I disconnect the pump from the rest of the system and put a guage on it, it reads about 22 in Hg and does not go up or down based on engine speed. When I shut off the engine the vaccum leaks back down to zero within 30 sec to a minute.
Also there is a little oil in the vaccum lines. Can this oil come from some other place than the pump or is that the only possible way to get oil in the lines? I haven't yet done a leakdown test for the rest of the lines but if there is a leak somewhere else I wanted to know how I could tell if the pump might be bad as well.

BTW: Where can I get a diagram of the vaccum system? Will that be in the chassis or engine manuals from Mercedes?