Is it possible that your plumbing is not unloading the pump when all of the valves are in their "neutral" position? I'm a newbie to tractor hydraulics, but have a fair amount of experience with industrial hydraulic systems. How long does it take to heat up, and can you hear the motor load slightly when any one of your attachments are actuated (you should hear this)? If things are heating up quite quickly (say 10 minues) it almost sounds like the pump is up to pressure and popping off the relief valve. All that power that goes into the pump to drive fluid goes directly into heat when the hydraulic cylinders are not actuated.
Again, newbie speaking here, but my Shibaura appears to have both the FEL valve and the 3-pt valve with a "tandem center" mode, where the pressure line dumps to tank with nothing operating. On mine, there is a (manual) ball valve supplying the FEL, it has to be closed to maintain pressure in the system and operate the 3-pt. Conversly, when the 3-pt is in the center position (solenoid unactuated) there is no pressure to operate the FEL, the 3-point sol must be energized "up". With both of these valves closed (3-pt up) the motor loads and you can hear oil flow over the relief valve. It heats up in about 10 minutes then.
I have no idea if my setup is typical or if this relates at all to what you are seeing, but if you are heating up that quickly, somewhere you are probably bleeding from the pressure side of the hydro system to tank. A stuck valve such as Buck describes would do exactly the same thing.
A question to you hydraulic experts here-what style of pump do tractors typically use, a vane or piston? Are these typically a "pressure compensating" (aka variable displacement) style where the displacement of the pump goes to zero when there is no flow?
Hope this helps.
Bri
Edit: I didn't read your last post carefully enough-that fact that your 3-point is drifting up almost certainly means the valve isn't returning to center properly, stuck between up and "hold". Would explain both the 3-pt travel and heat. Sounds like Buck is spot on again-should have known /forums/images/graemlins/wink.gif. Does the 3-pt drop normally? If so, you may be able to cycle the valve a few times and dislodge whatever is sticking things, fluid flow should flush it out then.
As to dismembering a solenoid valve-as you said, have a clean bench, note which o-rings go where (there may be several where the valve mounts, or one gasket) and don't force things. If the spool seems to stick in the body, work it out slowly and carefully. When you go to re-assemble, put a bit of oil on any o-rings, work carefully so not to cut them. If there are some between the valve and base you might want to "tack" them in place with some heavy grease, its pretty easy to shift and cut one when putting the valve on.
If worse comes to worse, are these valves a "industry standard" mounting?
Good luck.
