Thanks for your reply. Yes the first two were complete replacements but the new style seal was perfect fit from new so a little time in brake fluid made it just shrink enough to leak, then the next two were new pieces that I had to assemble. Yes I'm using DOT 3 and it is flushed for sure the past half year its probably had 2 gallon through it. And by the way it has a new sequence valve on it too. I thought of replacing the master cylinders just for kicks but it don't fit any technical reasoning. Every machine I have worked on I can reason why the part failed or can find the source of the problem but this one has me to my limits.