The first red flag is when bleeding with someone pumping the brake pedal, at any time did they run the pedal all the way to the floor? If they did, most likely the master cylinder was damaged. Crud and corrosion build up in the lower halves of the bores where the pistons don't normally travel. Running the pedal all the way down runs the rubber lip seals over that crud and can rip them. That results in a slowly-sinking pedal at first, then no pedal at all, and that often doesn't start until two or three days later.
The next thing is a scanner is often needed on some vehicles with anti-lock brakes to open some of the valves in the hydraulic controller. There is no other way to bleed the air out of some of the chambers.
Check the adjustment of the rear shoes, and look for a rear lining that is broken / rusted off the backing plate. That will cause a good pedal one minute and a low pedal the next minute.
Saturday, July 30th, 2016 AT 12:17 AM