Master cylinder problems

I have fitted to the series II land rover a later type 2.25 derv master cylinder moving away from the old type type with big nut on the rear. this new one is more like the clutch with a longer stroke putting more fluid out making it easier to bleed the 11"tls front brakes.

heres the problem when bleeding up it keeps its pressure and does release it pushing the shoes onto the drums making them bind however is you open a bleed screw and allow the pressure out the brakes then don't bind until the pedal is pressed again.

any ideals on whats going on?

is there anything like a one way valve in the old style bean can reservoir?

is there adjustment on push rod

yes theres is however i have been told that is only the pedal height adjustment but my local landy guys because its a sIII later type not the sII it has a butterfly valve that does not been adjusting to work well however this is only what o have been told.

how do i adjust all the pedal to how it should be?

the push rod needs to be either longer or shorter, i cant remember which way round it is. in the bore of the cylinder is a hole for resovoir fluid to enter, when the plunger is pushed in the hole is covered allowing fluid to compress and operate the wheel cylinders. your problem is the plunger not coming back far enough to allow the brake shoe springs to push the wheel cylinders in, pushing fluid back thru the master cylinder and into the resovoir.
adjusting it too far will result in fluid being pushed into the resovoir before the wheel cylinders start to operate, taking up valuble pedal travel.
it will take a while to find, and usually in 1/4 turn increments of the locking nuts.
hope this helps.

edit. just re read your post, i'm assuming you dont have a servo? mention of a butterfly made me think otherwise. if you do, disregard my previous post, as its a different setup.