Farmall 460 weak hydraulics when hot

OK so Ive done everything I could do without replacing parts. New oil, new filter, and I took out the cessena pump and checked it for wear and nothing! Every time I run my 460 for a few hours it will start loosing pressure in its hydraulics, and constantly try to lift the rear fast hitch with a load on it. (For example: After a couple hrs it will start to sink and relift my balers toung. You can hear it straining the engine a little as it lifts it). It also wont lift equipment with the regular hydraulics, like lifting a regular 11ft wheel harrow onto its wheels. So... what could it be? It just doesnt seem to make sense. Could it be in the valves? Any ideas before I tear into those? The fluids are all clear no bubbles or anything and no water; but they do seem to be getting awfully hot after a while. Is there some means of cooling that may be getting plugged and causing the fluid to thin out too much? I mean it lifts perfect when cold and works great and then all of a sudden it starts dropping. Any help would be great, Ive been workin on this one for days now and its gettin to me!

Matt: I'm calling the pump the problem, it may not look bad but you consult a hydraulic technician. In all my many years farming, didn't matter how big or how small the tractor, hydraulics getting slow when hot was pump, 100% of the time. That is considering filter is clean, oil is clean and full.

Alright not to say its not the pump but lets hope its not haha I dont have 400 bucks to drop on one yet, and its making a solid drawbar look better all the time. Anything else to try first before replacing the pump that might be cheaper. Id rather waste some time trying.... then the 400 bucks + shipping........

If you know someone with a flow rater, it might be worth the charge to check the system. A relief valve may be fading out also, it would be a shame to replace pump and not be that. Do you have aux valves, if so are they acting the same way?? When you had pump apart, did you pull the wear plates and check the seals under it.
Jim

I do know someone who might have a tool like that he works on big trucks, Ill ask him. But yes I checked the seals and they seamed fine and the plate showed no wear. The tractor has been in the family for 15yrs and my father replaced the pump when he got it but then it sat for 10 years. So its really only 5 years old or so. I just cant imagine that being the problem. But the valve for the 2pt hitch and the valve for the rear hydraulic lines are both acting this way. So is there a valve for the both of them? Are the valves under the steering wheel where I would find the relief valves? Would these be the ones that I would need to check?

Make sure the hoses to the hyd cyl. for the fast hitch are in the right ports. There is a check block to hold the fast hitch drawbar up. As you stand behind the tractor. The 2 ports in the seat box that are furthest apart are the ones the cyl hoses go to. Also the hose on the cylinder that is closest to the center of the tractor goes to the top port on the check block.
If the hosed are wrong or the cylinder seals are bad it will leak down & keep your hyds on pressure, heating the oilcauseing the problem you describe.

Normal operating temperature is 100 degrees over ambient temperature. Anything above that would be concidered hot. If the system is indeed running hot then the system is staying on high pressure. The unloading valve is suppose to dump oil back to the sump when you are not using your hydraulics to prevent the oil from getting hot. Hot oil is thin and easier to slip by the gears from the high pressure side of the pump to the low pressure side. Does it sound like the engine is laboring all the time like you are constantly using the hydraulic system. Sometimes the tel-a-depth valve spool will hang up in the valve and not return to neutral and keep the system on high pressure. If you have weak hydraulics to the auxillary valve only then you need to check for a blown o ring on the check valve piston.
Chuck

You need to determine if system is staying on high pressure when valves are in neutral position. Easiest way is with a gauge in the plug at pump mount. Should read less than 100 psi in neutral and about 1200psi with valve on demand. Other ways is to listen to engine when using hydraulics. With no load on the hitch, lower it way down, then let it stabilize for a minute, raise hitch and if engine seems to run more freely while raising than it does after it stops, your system is staying on demand. Another way, dead head an aux valve, it should cause engine to labor. If it is on demand already you will not notice any change. Note, this may not occur until system has started to warm up quite a bit or it may happen immediately depending on what the problem is. Most usual problem is one of aux valves has been turned too far where you change from single to double action and bent or broke the roll pin stop. Next most common is that the teledepth valve for hitch wears at regulating land and allows more fluid to escape than can be supplied through the screened orfice in regulating valve assembly or the screen is simply collapsed and plugged. So, you need to determine if it is staying on demand before we go into the ways of repairing it. May be that it is not getting excessively hot and pump is just worn out. Relief valves are near bullet proof on these models but the regulating valve is a different story. Both in same block. Like has been suggested already , a flow rater is the way to go, but if you do on these models the correct place to measure flow is from that port on pump mount that way you can close it off and check neutral regulated pressure as well as flow and max pressure of pump.

A 5000 lb liquid filled gauge is about $17.00, much cheaper than a pump and can give you some of the answers your looking for. The symptoms you describe do make the pump look guilty though.

-Leon

Its been raining all day today so I cant go out and try any of these ideas yet. But the last two responses regarding the valves sound more like the problem Im having. The pump has plenty of power to raise and lower anything its just when it gets hot it is constantly causing the engine to labor to keep the drawbar up. So it sounds like it may be that stuck valve that was discussed and its either keeping it open or its not allowing the fluids to return properly. Either way it sounds like I need to open up that valve assemby and do some cleaning and checking to make sure things arnt getting stuck or that those screans arnt plugged up. (this tractor sat a while so it def. could have some stuff in there) Ill post when ive opened it up. For now any tips on opening the valve assemblies? anything particular to watch out for? Thank for everything everyone this is a huge help.