GS 506 grader XCMG GR165

Good afternoon. I apologize for my English, I use Google translator. The problem is this. Installation of 2d GS 506 with priority valve on XCMG GR165 grader. Launched everything works normally. There was a problem when moving from object to object, the hydraulic oil is very hot. Distances of about 30-40 km. At first, there was a regular priority valve OLS 80. I decided that I replaced it a little with the OLS 160. Now there is a problem with him that in the work heats up to boiling oil in the hydraulic tank. When moving, no. I don't have a hydraulic circuit from a grader. But I don't like that my priority valve is not as in the classical scheme between the pump and the grader hydroblock. In fact, it turns out that there is a pump, then some kind of priority valve of the grader itself and only then goes from it to the hydraulic distributor of the grader. And I have already put my priority valve in front of the hydraulic distributor. Who can tell me where I made a mistake?