forget what I mentioned about the auxiliary valve setup in front of the seat, I was just guessing what you had without all the information. What you have, I believe it a divirter valve changing the flow of oil from the three point to the loader. What I think is the problem is the return line on the left hand side of the tractor is hooked to the presure side also. From what "Hutch who goes by shona13 has said in another thread where the op asked where he could check the hydraulic pressure of the pump, I believe where you have that line hooked is one, the other is on the cover that was replaced by the diverter valve and the last is on the right hand side of the housing under the diverter valve. If your return hose is long enough. Take the fill cover off by the shifter levers. Disconnect the hose, intall the plug back into the housing, put the hose in a short distance into the fill hole being sure not to be caught in anything and cover the balance of the hole with a rag to prevent splashes and start the engine at a slow speed and try and operate the loader. Someone else on the hydraulics forum wanted to do this and JJ told him to change the fill cap so a return line can be hooked to it. That my best guess. Maybe someone can confirm this. I don't know of any other place to hook a return line. Good Luck
namyessam