Pontiac Repair: no Brakes after bleeding system, wheel bearing, wheel cylinders

Question
2001 montana van. 3.4L not extended model

changed two back brake lines.  bleed the system. worked fine for a mile than loss of brakes except little bit on front drivers side . rebleed system  same thing.  changed master cyclinder with new master.  bleed fine pumped up fine  had brakes lasted a mile.  same results.   after failure of brakes again after changing master did  abs modulator and bleed them from top.  can find no leaks anywhere lines calipers etc..  any suggestions before I tear out what little hair I have left in frustration.

abs light is on but have changed both wheel bearing also. Spoke to a mechanic he said even with abs light on would give me normal brakes.  read online that you need a scanner to bleed these systems. mechanic said no you don't and told me how to bleed the abs module.   HELP  
thank you for time ...

Answer
Hey brad:

You right you need a scan tool to run the abs module as to bleed the air out of the chambers in the unit. untill then sadly your out of luck. every time you changed a part you induced air into the system and if it gets trapped in the abs module or traction valve depending on the year and configuration of the brake system on the van it gets trapped inside the chanbers of the unit and a scan tool need to be used to move the air out of the unit and further down stream so it can be led at the calpers and wheel cylinders. Sorry for the bad news.
Good luck ;-)