Power Steering issues

Pump or steering box. Power steering is pretty much a hydraulic system. If either the pump or box is worn, oil bypasses. If its bad enough it'll cause a pressure drop. Or it could be a failed valve in power steering box. IIRC the power assist is actuated by tension on the box's input shaft. If that valve screws up it can't direct oil to the end of the piston inside the box for the assist.

With stuff like this its important to go to a shop that knows how to diagnose. A flowmeter is pretty much a must for diagnosing the system. Picking and choosing parts to replace gets spendy real quick.

 

I had a problem with steering getting harder as the day went on, local shop put on new pump, not better, went to a shop in Houston that rebuilds pumps. He put a high flow pump on.
Left the shop and in about 10 miles the steering started locking up. Got back to shop and changed the steering box.
After a year of having hard steering I had a hard time driving home, took a few days to get adjusted.
I had 2 shops say it wasn’t the steering box, but as it got hot it would bind up, don’t think any shop would say it’s the box. You may have to insist they change it if nothing else works.