Extend the cylinder and shut the engine off. Crack the hose that is not suppose to have any pressure on it. As I understand it you should be able to take that hose completely off but just loosening it should tell you. If you have oil coming out of this fitting the cylinder piston seal is leaking by. If there is no pressure there the valve is likely the problem.
This is what I've been told anyway. Be careful when loosening any fittings as you might get sprayed.