This is my 1st post. I had the pass side brake of my 1990 Chevy Pickup grabbing. So I replaced the caliper and pads on both sides... Couldnt get it to work (soft pedal) so I replace the Master cylinder. I bled it . (Althought the MC did not come with the little hoses just plugs to bench bleed it) Now the pedal feels pretty good but when you start the truck the pedal goes to the floor. I blocked the back brakes off (front part of MC) with the plastic plug that came with the MC. And when you pump it the fluid for the front is saturated with air bubbles to the point it looks milky that goes away after 10-15 minutes. Am I doing something wrong? Ive done alot of brake jobs on my cars but have never run into a prob like this. I think it has some kind of Crude ABS on it ( I may be wrong) Could it be the brake booster? This is really strange. I sure would appreciate the help . thanks!!!!!!!

 

I got a '90 chevy also...I have had a similar problem...Couldnt get the the brakes to bleed out after I replaced the MC...turned out the new MC I got was defective. changed it for another one and been working fine since...
Good Luck