I have standard front brake master cylinder, & new grimeca caliper set up, I had a look at the piston, seals etc., in the cylinder and the piston had a bit of corrosion on it so I got a kit and replaced all the parts. when I put it on and connected up it pushed oil through it no problem but the caliper pistons would hardly return leaving the piston hard against the disc. thinking there was something blocking the return I stripped down the master cylinder and reassembled it, it will not now pass fluid!. On the bench if I pour fluid in it will come out the hose connection where it's meant to, if I fit the spring with the valve and plastic piece and the primary cup, put fluid into the reservior and push it in and out with my finger I get fluid coming out the hose connection, but when I put the piston ass. in nothing comes out, the fluid in the reservior doesn't go down which suggests a blockage but all the holes are clear, I even put the old parts back in and still nothing is coming out, It's got to be something very simple but I'm banging my head off a brick wall here and missing it. Hopefully somebody can shed a light on what I'm missing.
Cheers
Cheers