Block the steer cylinder in the center position, remove the return hose on the un-pressurized side of the cylinder and steer in that direction. A bi-directional, non-differential steering cylinder shell will wear in the straight ahead or center position. If oil is bypassing the packing (oil coming out the return side of the cylinder) while in the center after resealing the cylinder... the cylinder shell is worn and needs to be replaced. Two simple tests of the hand pump/rotary valve is when bottomed out (full right or left steering) is it fairly easy to continue turning the steering wheel. Secondly, can you steer the wheels with the engine off? Of course it will be harder... no power steering. But there should be little slippage in what happens at the steering wheel to what is happening in the steer wheels.