I would first check cyl. bypass by deadheading tilt cyl`s all the way forward. remove the hoses from the front of each cyl. then continue tilting forward. there should not be any oil coming out. also try it by tilting back and removing the rear hoses. this is the easiest way that i know to eliminate the tilt cyl`s from bypassing. if cyl`s are ok, then check the tilt lock in a similar mannor (if equipped) then move on to the control valve.