If you can get a firm pedal the master is likely good. Pull up the handbrake and try again. If the pedal stays good with the handbrake set then the problem is the rear brakes mechanically. How did you adjust the rear brakes? Are the brake cable properly set? The handbrake can only be adjusted with the drums removed so you can check the gap between the lever and adjusting rod. Yes, with the handbrake down there needs to be a little clearance. Otherwise the self-adjuster won't work. Are the top springs installed properly? The hooked ends have to face up. Are the adjusters installed correctly? Side does mater rear fork gets set with longer piece in the shoe slot and short piece facing the drum. Front the bevel faces the backing plate. 

If all that is good the next candidate is the rear brake pressure regulator. I also fill the brake light switches before installation. Since fluid cannot go threw them some air can be trapped inside. Some of them have considerable air space. A bad regulator can also cause that need to pump up effect. 

Dennis

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of Mike Riley
Sent: Wednesday, February 4, 2015 3:47 PM
To: vanagon@GERRY.VANAGON.COM
Subject: master cylinder problem thoughts?

I am on my second new master cylinder First was a beck-arnley and it squirted back into the reservoir on the down stroke, out it came now with my second different brand I have to pump the pedal once to get a pedal at the right height. No air in the system and the pedal is firm both at the low position and at the pummped position. Bled 3 separate times using 2 quarts fluid total and there is no air and no loss of fluid. this is my ninth van so I have done many brake jobs. New rear cylinders with the springs in them and brakes adjusted tight. I guess that I have received a bad master yet again?
thanks
   mike