I'm replacing the master cylinder in my '79 Catalina right now, and I want to make sure I've bled the cylinder correctly. I put the plug nuts in the two holes and filled the two reservoirs with fluid. I then took a rounded, blunt metal object I found in the garage that fits in the depression for the pedal arm and gently pumped the piston in and out 3-4x. It became really hard to move by hand, so I mounted it on the booster and used the extra leverage from the brake pedal to press on the cylinder. The pedal is practically rock solid.
Sound like you did good. For a double check I would also pump the brakes after car is "on" for a sec. If it feels at all squishy you can probably tap out the remaining air through the lines since it can back feed back to the master. Just keep the fluid topped off and I think you did good dude.
I hooked it all up, the pedal didn't loosen up until after I fired it up. It started getting spongy. The line I just replaced yesterday popped at the wheel cylinder, so I'll need to look at it again. Pumping the pedal builds pressure to normal, that by itself is a serious improvement. The pedal used to go to the floor, lol.
You still have air in there - the line that popped is obviously a prime candidate for the cause.
I think the line popped a few minutes after I put the MC in. It was feeling pretty good initially. Then I did notice it seemed to want to sink a bit more. Next weekend I'll cut the line and re-flare it again. The flare cracked a little, and my girlfriend's dad said it may be ok. I'm willing to bet that's the cause of the leak.
I noticed when I was pressing the pedal that this cylinder still bubbled quite significantly in the reservoir before I put the lid on. Will air in the lines of these old cast iron monsters cause that, or does it mean the booster/ cylinder have a hidden issue? I noticed there is still a very slight seepage at the rear of the cylinder when I ran out of daylight, so I may need to take that cylinder back. The booster works fine as far as I can tell, once pumped up, the pedal wants to stay firm, but that rear leak gradually bleeds off pressure. Pumping the brake when the car is off does exactly what it should -gets more and more firm until extremely difficult to move. It does, slowly, due to the leak. The near proper function is new.