Brake Pedal to Floor after bleeding

Hi, Really at my wits end with this car. Bought this 1984 500 SEL about a month ago. The car had sat for approx. 1 year. A DIYer I put new pads, rotors and two new calipers on. This car also has the ABS. Bled brakes and pedal slowly went to floor. Stopped the car but took some pumping. I don't plan on driving till I have a good pedal.

I thought the problem was the master cylinder. Put that on 2 days ago and still no hard pedal. Lines are not leaking from what I can tell. Old fluid is out of the lines since all clear brake fluid is coming out the bleeder screws. Had a friend pump the brakes and belief we consistently followed the correct procedure to insure no air got sucked back in. Intially there was a great amount of air, but that has been quite awhile ago.

Then today, we bled again with engine running. Still no air is coming out, just fluid yet no hard pedal. Is is possible to have bought a bad M/C? Should the car be tilted any certain way? How can air remain? Any ideas would be a blessing! Thanks
Bill