I can't get a solid brake pedal on 1990 Toyota 4Runner

I can't get a solid brake pedal. I've replaced, master cylinder, booster, back brakes, brake box located front passeger side and bleed. When motor or switch is off the pedal is hard but as soon as i start goes straight to the floor. If I push while idling pedals goes all the way down and i have brake but couldn't stop suddenly.I've bleed over and over again, Can you help? Thank You Sue

by in Knoxville, TN on November 23, 2010
2 answers
ANSWER by on November 23, 2010
what about your wheel cyclinder?
ANSWER by on November 23, 2010
is wheel cylinder good adj rear brakes did you binch blead master cylinder first before you put it on ,mastercylinder may bebad or you have a lot of air in . pump up bleed each line on mastercylinder 1 at a time pump up hold down bleed rr wheel make sure you get fliud to wheel next LR,RF,LF make shure you keep mastercylinder full of fliud