Resurrecting a decade old thread because I have the same issue as OP, or a little worse. Brakes won't bleed, at all, at the front. I've tried both vacuum and pressure based (Motive) and can't get a drop out of my new front caliper.
So now I've got new front lines on order in case there's a blockage. If that doesn't fix it, what's the logical next step? Master cylinder?
Also, I'm mainly a Jeep person, though I've also worked on some Porsche (928) and very new VW (never had to touch brakes) and a lot of Japanese stuff. Can't say I remember coming across the little pushbutton pumps on top of the master cylinder. They seem to move... something when pressed. What is the point of them?

(vehicle is an '83 240D)