Brake Bleeding Woes...

[Lunch2000]

I decided to finally do the brakes on the Supra, they have not been bad but they have not been great. I've been meaning to do them since I got the car a year ago. There were the requisite lumps that used to be the bleeders and the brake fluid was black. To make a long story short replaced all four calipers and pads + new rotors in the front. Drained the brake lines - this may have been my fatal mistake. I now am not able to bleed the brakes properly. I bled the master cylinder according to the TSRM and it does not *seem* like I have any air in it. When I try to bleed the rear passenger caliper, I don't get really much of a flow out of the bleeder. Air does get pushed out but any fluid seems to come out very slowly if at all. Even though it did not seem to be working well I went ahead and bled them in order. I did get a good amount of fluid out the front. The issue is the system does not seem to hold brake firmness. You pump the brakes and they get hard but then after 10 seconds you can push pedal to the floor again. Is this symptomatic of air in the system? I do have ABS, I am planning on trying to pressure bleed the system this weekend to see if that will bleed/flush the system properly. Any further tips/advice on what I may be doing wrong?

Lunch2000