I've had the exact same trouble bleeding a brake system that was completely
rebuilt a number of times. The solution for me has always been to first bleed
the master cylinder by opening the connection at the output of the MC. I.e.
loosen that union, press and hold brake pedal, tighten union, release brake
pedal, repeat until you get pressure.
Another trick that works well is to pump the pedal violently with all bleeders
closed, then hold down the pedal and open a bleeder. This probably isn't a
very good idea with DOT 5 though.
I think the reason that a dead empty system has trouble pumping up is that
air can move through the system so easily that there isn't enough back pressure
for the seal to close, or something like that. (Psst, don't look at my hands,
or you may catch them waving during the previous explanation).
Joe
|