anyone looking at this forum, if you are experiencing difficulty with diagnosing a faulty hydraulic clutch on a ford transit where air is continuousness entering the system don't bother wasting your money on a new master cylinder for the clutch or slave cylinder as you will find it is pretty in affective as the problem will still exist, I advise that you spend your money replacing the connectors that push fit into the slave and master cylinder as the rubber o ring can degrade allowing air to enter the system causing the clutch to completely disappear. If you bleed the system and find that the hydraulic fluid contains many small bubbles of air then this is a good indicator that the rubber o rings on the push connectors have worn.
harry
December 2012