300U Power Steering,Priority valve problem

[redgems]

Fellas I restored a 300U with power steering.
Power steering works beautifully . However , the hydraulic line from priority valve to steering unit surges.
At low to medium speed its noticeable on engine sound .
Any ideas what I need to check or correct.
Thanks,Tony

 

[Janicholson]

If the pilot valve in the regulator block is plugged, or the small screen associated with it is plugged, the pulsation will happen. The little valve is responsible for pressurizing the hydraulic circuits when the levers demand flow. Look at the parts diagram to find it (should be in the first module closest to the reservoir). Jim