Cannot acheive hard brakes

Good Day. Removed front calipers - new brake lines installed ,along with prop. valve. Repaired all visible leaks, bench bled master cylinder and all lines in proper order. Several times. Still have a pedal that goes to floor on first pump then hardens after two or three. Goes to floor after sitting for min. or two. What can be wrong. I am out off ideas. Help!

Not sure that I am qualified to help here, but here goes. You would know th efront and back circuits are separate and so can be bled separately. The equalisation valve may need to be reset in the middle but I would think should not cause your symptom. I would be looking to see if there is any air in the lines when you bleed them. The pedal will go down obviously if there is air or else if the master cylinder is leaking internally but cannot think of any other reason.
Did you rebuild or work on the master cylinder? Is the fluid level changing in either circuit when the problem occurs?
Just thoughts.

Rgds

Sean

Good morning. Have taken master cylinder off to work on the brake lines and engine compartment. May have been damaged during long lay up on the shelve??? Will try and rebleed lines again. If you have any other ideas please feel free to share. Thanks so much.

Sounds to me like you have a bad Master Cylinder. Once you have a hard pedel if you continue to hold it will it slowly drop towards the floor?

When you are bleeding the brakes are you having a buddy pump then hold the pedal as you crack the bleeder screws or are you using a different method?

Did you try cracking the lines at the Master Cylinder while a buddy holds the pedal? Really hard to do that with out getting brake fluid on the wrong places....paint really isn't a fan of brake fluid.

Good day. Finally managed to acheive a good pedal and brakes. Combination of probs. New master cylinder installed along with extending the push rod to its proper length. Reguires 1/8 inch space from end of rod to M/C piston---mine was 3/4 inch. Most important was the bleeding of brakes. Had to remove calipers and hold the bleed valves verticle or at right angles due to the way the calipers are cast ,if left on our Mach they will not bleed 100%. Hopefully this will help someone else from having the same frustration.
I thank everyone for their good advice.

wow that sounds like an ugly set up problems. Well done for sorting through them!

Sean