I just bought a Farmall 340 with the engine driven hydraulic pump at the timing gear. The hitch lifts strongly--it will lift the tractor off the ground. But when the control is in the neutral position, so the cylinder is not active, the pump is pumping full pressure against a closed system. There doesn't seem to be a working dump valve that is putting the fluid back into the sump/transmission. The pump and tubing get very hot and finally the engine will stall out. I've seen the question raised on other panels, but while the question is common, there are no answers. New fluid and filter didn't solve it. I've torn part way into the regulator valve and it looked clean and the o-rings seemed tight. There's a very powerful spring in the "safety valve" that seems solid. I can't pull the safety valve piston at the front of that because there's no way to get a hold of it. I wasn't able to get the regulator valve completely apart, either. The piston comes out, and the o-ring seems to be tight. There's a ball bearing valve behind that, which the piston apparently is supposed to activate. It moves freely, though sometimes makes a snapping noise when I push the piston into it. I can't get the valve seat out. All the orifices in the cover plate are open and clean.
Am I even in the right area? Any suggestions on what the problem is, and what tool I need to get the regulator valve seat out? It looks like I need a screwdriver about an inch wide to hit the slots cut into each side of the seat.
I know the pump pressure is the problem. When the cylinder is in motion, the engine rpm drops. When the cylinder is not in motion, the engine is laboring against the pump pressure. It ought to be the reverse of that, with the engine working harder when it is lifting the hitch.
Thanks! I've learned a lot from other posts on my other equipment.
My 1943 M is so much simpler.