Hey guys, I got a 27 Ford with one of those 60's Chevrolet truck duel master that uses a hydrolic clutch. The owner brought it in, can't get the clutch to work, no pressure out of the master. I've pulled the master apart, it has a new rebuild kit in it and I'm not seeing anything wrong except when I pull up images of rebuild kits there is a part I don't have. I don't have the brass thing with the hex in the picture below. What is it (check valve?) and where does it go? Maybe what's wrong?