Welp,
Welcome, sounds too familiar. I had this same problem on the clutch side, I was using a MITY VAC to pull fluid threw but before I could get the bleed screw tight it seemed to allow air to draw in, if you bleed with the pedal it may be that the little shuttle valve is cutting off your flow to the brakes as designed sensing a brake or what it thinks to be a brake in the line. ie front and rear system? I have not figured threw this but maybe a pressure bled set up would have a better out come. By the way the vacuum way was miserable at best, I finally went with; http://www.speedbleeder.com/ these helped but were not a cure all,
Mark
PANTERA INTERNATIONAL
A DE TOMASO CAR CLUB
Presents the De Tomaso Forums
The On-Line Meeting Place for De Tomaso Owners and Enthusiasts From Around the World
Clicking on the banner will take you to the sponsor's website.