I just got done doing a disc brake conversion and pulled a full quart of fluid through the system using my Mity-Vac (8 oz. per wheel) and still have air in the system. The Mighty-Vac has failed me the last few times I tried it. I think what is happening is the vacuum is pulling air in around the threads of the loosened bleeder screw.
Went and borrowed a pressure bleeder and all is well.
This is the reason I use a dab of silicone on the bleeder threads.
