Working on my '89 300E. And I know for certain that I have at least one leak somewhere in the vacuum element/hose system for the climate control. And I'm one of the smarty-marties that sprung for the factory CD that by coincidence has a section on trouble shooting this system. Before I get started, though, I have a question. And this question lies in the conversion factor, because I'm going to be using a pump that is marked in PSI, and not mbar, which is the factor the service CD uses.

According to the coversion chart I've seen, the formula to covert PSI to mbar is: mbar = psi x 68.97

If this is correct, then it would only take about 6 psi to get the required 400 mbar that the service CD says I need to test the system. And the reason I'm concerned is that this really isn't much vacuum.

Does this mean that these are really delicate valves/lines and I might suck one to pieces by applying more vacuum than that? Surely the motor pulls more vacuum than that! I just want to make sure I don't break something by applying 10 or even 15 psi just because I get a little excited with my sucking machine! Sorry. I couldn't resist.

And my other concern is that I can use a, and don't laugh too hard when I say this, hand pump instead of an electric pump. I'm asking because I don't know how steady of a vacuum source the system, when working properly, requires.

I knew I shouldn't have posted this. But if you can pick yourself up off the floor long enough, I'd appreciate any serious answer you can give.

As Always.............