on our 9750 the spring broke in the valve that closes the flow that makes the pressure build up. this kept the flow blocked and the system was like you were holding a button down all the time causing the oil to overheat. when you push a button two valves will activate, the one to stop the bypass and the one where the oil is supposed to go ie header , unload auger etc. the common valve is maybe your problem. It sounds like you have a hydraulic load all the time. In an old 8820 the unload auger valve would stick when we swung it in causing this problem.