When the pedal hits the floor, you probably still have air in the MC. So bleeding the lines won't help.

If you have a partner, as Gman suggested, you can bleed the MC while on the car. Crack the lines open, have partner depress pedal slowly till fluid comes out. Tighten line and then have partner release pedal. (If fluid doesn't come out first pump, tighten, release pedal, try again.)

Basically you're pumping out the air and then by closing off the line the MC sucks in fluid from the reservoir.

You may be able to do this without a partner if you get a length of wood to jam between seat and pedal to hold the pedal down while you get out and tighten lines.

Also, brake fluid softens paint.
--
1980 245 Canadian B21A with SU carb and M46 trans

You do realize there are 10 bleeders screws, and each one of them have to bled, right?

What exactly doe sthe brake pedal do?

Hard pressure and it holds, moderate pressure and it gradually moves floorward? That's the classic failed MC symptom. Hard pressure flares the piston seals tightly against the cylinder walls, and moderate pressure does not - allowing fluid to by-pass the piston.

When bleeding did you use a helper pushing the pedal?

Do you have ABS?

Good Luck,

Bob

:>)

I bench bled new master cylinder....didn't work, so i exchanged it for another (they're remanufactured) bench bled and installed. Calipers are original, and were not switched between wheels.

I vote for bench bleeding the master cylinder. I would get one of the kits (some new master cylinders include them in the box) and attach the lines to the outlet ports and run the hoses into the reservoir. Pump the pedal slowly to remove all the air from the master cylinder before attaching the brake lines and then bled the system in the correct sequence.

You didn't replace the front calipers did you? You don't mention that but it wouldn't be the first time someone installed the front calipers on the wrong sides and had air trapped at the top of the calipers and no bleeder valve on the top to allow it to exit.

Randy

Did you bench bleed the master? Have seen where it just won't pump fluid to the calipers until this is done. Can do it on the car, just remove the lines and cover the holes with your fingers. Pump pedal-cover-release pedal. Doesn't have to be perfect, just get some air out.

i guess you have adjusted the rear brakes ?