It appears in my research that the ABS can have air bubbles which are difficult to evacuate, been through three bleeding procedures and cannot get full braking, worse yet, brakes lock up when hot at precisely same point in daily drive. Pressure bleed, but very little air came out at calipers. Unlocked the proportion valve which was preventing rear brake bleed as the brake line ruptured and had them replaced. So this is where my problem started, got stuck taking it to a independent who supposedly knew BMW's, yes he came back and said I need master cylinder when he could not bleed rears, and he had no diagnostic system evidently. So got screwed, took it home on front brakes only, replaced master cylinder and no difference, which led me to researching issue myself, bought the bleeder diagnostics, got to bleed rears, but using vacuum bleeder was not working, bought pressure bleeder, got more air out, but still same issue of soft peddle and only 50% braking and still locking up. I read that jacking up rear is solution for stuck air bubbles in master cylinder, so I am stumped, will try to bleed again. Any suggestions?

Thanks,