Power Steering Question

The centering is controlled by a spring in the control valve. I don't know how the steering wheel could keep turning without stopping. That might be something in the box.

So the power steering was installed in the car when it was two years old? Is it a stock setup?

If there is binding in the ball stud of the control valve, then that may keep it from returning to center. When you aren't turning the wheel, the hydraulics basically center and go into neutral. The wheel alignment and the torsion of the bushing in the idler arm are what makes the car want to return to center. Could be the car needs more camber (I think that's the term) or the idler arm bushing could be bad.

I don't understand what you mean by the steering wheel feels like it doesn't stop. You said you turned it fully, but it didn't stop. How do you turn it fully without hitting the stop? If the original manual steering box was left in the car, the steering wheel should turn no more than 2 1/2 turns either way from center.

The idler arm might need to be changed to one made for a power steering setup. I understand that the tension of the rubber in the idler arm can aid in returnability and the arms for power and non-power linkages are different for this reason.

Also the caster in the front end alignment may not be enough to aid the return of the steering to center.