Power Steering box turns hard left when steering wheel released - yikes!

The valve is stuck or you have debris in it.Take the 2 bolts holding the low pressure fitting off and remove the big fitting at the back of the valve along with the screw in high pressure fitting. Dont loose the o-rings. Push the round valve out inside and remove, clean everything up so that the valve moves freely and make sure the little screen is also clean. Fill and bleed. Sometimes it seems to take forever to bleed the system!