I had a wheel cyl leak on my 84 D150 so I replaced both wheel cylinders as they looked like originals.Bleed system and get real good pedal feel. Ah another job well done. Next day I get stuck in trafic and the pedal starts to feel mushy but not every time. A couple of days of this and the weekend comes up so I figure that when the leak happend the travel in the master cyl increased and maybe there was corosion i n there and the master is starting to blead by some. Its 25 years old so I get a reman and Bench blead the new one and install. pedal feels good so go ahead and quick blead all 4 wheels just to make sure every bit of air is out. Make sure to keep the resovors full and after I'm done go to test drive and pedal goes right to floor after a slight hesitation about half travel. Look for leaks-none. repet all the bleeding procedures and the pedal just goes to the floor.
Notice that the brake lite will not go out. is it posible that the proportioning valve can stick and bleed fluid internally or is my reman master bad? and has anyone rebuilt or tore down a proportioning valve? I cant seem to find a replacement at the parts stores.