I took a small drill bit and used the shank end to probe and there was no resistance or anything that felt like I was hitting a rubber seal. I took one of the other Mc and pulled the brass nipple out and there was not a residual valve there. I also checked the port for the rear brakes and no residual valve in there either that I could feel. I am now leaning towards either the nipples in the distribution block being squeezed almost shut or the rubber lines collapsing