I think there is a way to over flow the suction tank. Overheating the ps fluid. There is a loop in front of the radiator for cooling. It may be blocked with leaves and stuff or pinched. It is flushable. The pump pressure is highest when the system is cold right after starting. Anything related to the relief valve would occur then. What happens if you idle for awhile? Same problem? Is it heat or engine rpm that makes it come out? Could be the blockage if RPM related.