Nissan terrano d22, 4x4 address bomb problem,

Estimated
for a while now, the direction of my terrano truck, (frontier elsewhere) comes with a problem, which being parked or turning in a corner, behaves like a mechanical direction. Remove the pump, I checked all its internal components and look in good condition, the pump is a VK-513 type. I did everything indicated in the different videos and informative that I could read, however, I can not repair the failure. I use the right oil, and the belt is good.
I only doubt the flow valve .... maybe it is being stuck, but I have no data to check the pressure or other way of verifying it. Can someone give me information or other valve inspection, at the moment I have it unarmed and can revive it? Of course, thank you very much for your help

Good compa, definitely the common failure in the Frontier is the check or high or flow valve as you flame it. The symptom is that it loosen when you drive and harden when you are parked, but ... if you are parked and give it engine revolutions the direction is loosen, if this is the symptom because you will realize that disarming it is impossible since it is sealed, it changed that it is not very expensive and then with the two front tires of the car in the air, fill the Power Steering fluid circuit, tour the direction of the direction about the direction of left and another to the right. Then you turn on the car and repeat ten to the left and ten on the right, if you do not do the circuit, do not purge (from experience). Luck!!!

Well friends.
Indeed, the problem was the steering hydraulic pump, it had a game (wear) entity the axis and the rotor, this added to the fact that the flow control valve was broken in the guide sector, this caused that there was no pressure ..
thanks to your information and advice ...