Hi mates

I have a weird issue I hope someone can help me with. A few months ago I installed a brand new master cylinder and a complete rear disk brake conversion (with SS lines). I have a weird issues where it seems that the front brake reservoir is draining into the rear one. Example. This evening I drove my Z from my parents place back to mine, roughly 30 minutes of driving. When I was leaving the front brake reservoir was on Low and the rear one was on full. Get to my house and the rear one is completely overflowing and the front one is slightly lower then it was before. Is it possible that I have some sort of back flow issue here?  This isn't the first time this has happened (actually the second) and I thought I had fixed it. (Mind you I haven't driven the Z for more than about fifteen minutes in about four months).

Thanks mates

Cheers
Jan

There are four seals in the MC.  Two to pressurize the front and back systems, one to keep them separated, and one to hold all of the fluid in the cylinder.  Seems like your separator seal is not separating.  Not sure of the actual dynamics but that seems reasonable, to me.  Looking at the drawing it seems that fluid is pumping back and forth to various places with each pedal press.  In your case it might be that the port to the front reservoir is clogged and fluid is getting forced past the separator seal (had to take a guess).

Short would be - your MC is bad.  Best guess.  I found that some of the hydraulic parts I bought at the parts store had machining grit in the bores.  Best to take them apart and clean them before installing.