I have a Kubota B7200 4wd with a front end loader and box scraper on the three point. When I first start up, the loader and three point operates ok, but after running for a while, the lift on the both the loader and three point gets really weak and will barely lift a half load of dirt or the box scraper. I checked the filter screen which was ok, and changed out the hydraulic fluid, and this did not help. Seems like the fluid is bypassing, so maybe the pressure relief/bypass is shot? Not sure if the only bypass is on the one on the spool? Can the bypass be rebuilt? Am I on the right track? Maybe the pump is the problem? Any suggestions on how to troubleshoot the problem?