Trouble bleeding brakes

UPDATE: so i gave up this week and invited my local mechanic by and told him to bring his best scanner...so he stopped by yesterday and gave it a whirl....his scanner wouldn't bleed the brakes....it made the abs unit make some minor noise, but that's it....pedal still to the floor ( almost). so i figured i would take the RV out of the barn and go find a nice muddy field that i could " exercise the ABS"...well i took it off the jackstands, put it in reverse and the brake pedal was NICE AND HIGH! WTF! so feeling brave i drove it around a bit and now all is well. no funny noises from the hydroboost, good firm brake pedal.....so i'll need to think about this one for awhile to find the secret lesson to be learned....