DDK - Die Deutschen Klassiker

so, i have filled up the system and bled the brakes on my '69 coupe, exactly as per the orange book, with the wife merrily pumping away, and appeared to get good fluid out of each bleed screw with no bubbles but the pedal, whilst you initially get resistance half way down, with pressure maintained, it just gradually sinks down.
(i had all calipers rebuilt and a new master cyl, and i'm using Bendix Dot 4 synthetic fluid)
can this be anything other than a faulty master cyl? (i went through the whole bleeding proceedure on all calipers twice)

If there are no puddles then master cylinder is the suspect.

thanks...as changing the master cyl is such an unpleasant job, i'm going to try pressure bleeding first...anyone recommend any particular one?

EZI- bleed does the job. Just remember to seal off the drain from the reservoir or it goes everywhere. Guess how I learnt that...