I'm having fun with my brakes on the T3 Transporter. They are losing pressure but not fluid. Any clues? They load up and then fade to a point where they hold. If I pump them they do the same load up and then fade. they still work but I'm getting a lot more pedal play.

Sounds more like your vacuum booster.
Check for leaks of the vacuum hose.
Remove it and plug the engine side - same symptoms?

Thanks I'll give it a try