Air in Brake system

[smk_texas]

Hi,

I replaced the rear brake lines, hoses, calipers & pads on my 90 300D (w124) last week. When i bleed either of the rear brake calipers there is a constant flow of air bubbles on both sides along with brake fluid. I emptied two full quarts but still the bubbles don't seem to stop.

I checked the rear compartment of the reservoir and it is full. The brake lines are tight at the T junction in the back and absolutely no leaks. I am stumped. Could the rebuilt calipers be bad out of the box ????? I got these rebuilt ATE calipers from O'reilly's for $73 a piece. Please advise.
Thanks

smk_texas