Is My Master Cylinder Bad?

[tubbedII]

It was time to bleed the brakes last night, but didn't go well. I'm trying to run a used master I bought off the board, and wondering if it's no good. It was said to be fine and just pulled for a nicer unit.

I put the master on the bench to bench bleed it and filled it about half way. The 1st push of the plunger spit out a little bit of fluid, but after that nothing. It didn't bubble in the reservoir either.

A little frustrated I walked away for about 5 mins and came back to fluid leaking out of the ports. I pushed the plunger and it seemed like it was working but only for about 3/4's of the plunger's push. After that, the same thing, nothing.

Any clues on what may be going on or do I just need to replace it?