It’s probably a bad power steering control valve
In your reply to Robert Brotherton (July), regarding his power steering turning to the left at idle, I think the problem is more likely to be the control valve. The power steering system has a conventional steering gear with a power assisted steering linkage. More than likely, the control valve was contaminated or is out of adjustment.
Thank you for taking the time to write in and offer your advice. The control valve you mention does what its name implies— it controls the application of hydraulic pressure in one direction or the other depending on which way the wheel is being turned. If the valve is malfunctioning or out of adjustment, the steering effort required to turn one way or the other may be greater than normal, and the wheels may have a tendency to turn in one direction when they should stay straight.