Background: I was working on setting the Push Rod Adjustment on my 70’s a rebuilt Bendix Brake Booster. Adjusted it from the initial setting (shown) then realized that the instructions call for the setting it with vacuum on the booster. Set up my Mityvac and tried pulling the booster down to 20". At about 7" it would pull down not further and some times just dropped to 5". Checked the Mityvac and tubing for leaks, it held at 20". Should the booster be bleeding vacuum?
I ended up setting it connected to the engine while running. It hardly moved from the setting without vacuum. Still concerned with the apparent leak.
I’ve never set one of these with vacuum. Have I been doing this wrong all of these years? I get good results?
It hardly moved if it moved at all. I’m glad I adjusted it on the bench, it was easier.
To answer your first question, no the booster should not leak down. I have one on my workbench for over a month and still holding vacuum.
Catlover, Thanks for the answer. Not what I wanted to hear but it is what I needed to know. I should have stopped with installation before the weekend. Since it’s in and the system bled I’m check to see if it’s holding between engine runs. Maybe the little mityvac didn’t have a enough umph to seat something internally, wishful thinking most likely but I’m not real anxious to pull it out again. I’ll be talking to the supplier on Tuesday.
Sometimes you get to answer your own questions. It seems the little mityvac hand pump doesn’t have the volume and pressure to to seat and seal something in the booster. Engine vacuum of 20" is holding after an hour.