Fella on IH board says with hydro-vac, you shouldn't have a check valve in Master cylinder. He didn't really say why. He was talking about IH truck and fella that rebuilt his master, couldn't bleed them. I'm having trouble with big truck, which has the smaller truck new master in it, having slow comeback for pedal and fluid. Is that then because it has the check valve in master? I can pump mine up for better pedal, and it stays all the time I'm driving, just goes down overnight. When driving, slow recovery, feel brakes drag for few seconds and can feel it come back slow in pedal or watch it rise to stop in few seconds. What ya think?
