Bloody Master Cylinders

[Dolly-Nut]

Just spent 3 hours trying to rebuild my Sprint clutch master with outrageous joy.
As it stands the kit is fitted and semi-bled. When the pedal is pressed all that happens is the fluid gets pushed back into/out of the reservoir, what is going on?! Something obviously isn't right but I've checked it all thoroughly and there's only really one way everything can go. It was doing this previously when the pedal was depressed slowly but now it only does this.
Here's the kit:

#1, 2, 4 & 5 are obvious as to where they go. #3 I'm pretty certain hides inside that plastic cup thing on the end of the rod and acts like a washer, correct? #7 - is that an alternative main seal or?
#6 - can someone confirm which way round this goes on the end of the rod? This is the most likely problem but logic suggests in can only go one way because of the step it has.

[soe8m]

The little seal in the plastic isn't sealing against the back of the cilinder. Maybe dirt or corrosion.

jeroen

[xvivalve]

Check the bleed hole in the slave isn't clogged up.

[Jon Tilson]

What they said....

The little spring washer goes between the sprung rod and the plastic cup. Its actually pretty obvious and hard to do wrong.
There should be a diagram with the new seal kit if its a proper girling one. The little rubber seal goes on the end of the rod such that a narrow ring or lip protrudes above the flat circular metal tip. This is the bit that seals the opening to the reservoir and if it isnt working properly you will get what you describe.

Jonners

[Dolly-Nut]

Had another look at it today. Only thing wrong was that the spring was slightly bent so I changed that and it remained the same. I then changed the rod/one way valve assemby for an old one which was assembled in exactly the same way and everything looked identical (except the seals were old) and now it's fine?!! So it was something to do with that valve as I thought but what exactly I have no idea.