Kubota L245F with Bush Hog 1846QT FEL - Hydraulic burping and bounce on FEL and 3-point

[Banochris]

Recently I rebuilt the 4 hydraulic cylinders on the Bush Hog 1846QT and changed the hydraulic fluid in the Kubota L245F. I cleaned the filter as well. Everything works correctly, and strong for about 10 minutes. Then the 3-point won't stay in place (lowers) and the FEL lifts jerky and only a little at a time. The bucket does the same thing and will only lift a few inches at a time. I noticed a couple of things when this is happening.

1) Sometimes the bucket (not the boom) will lower when I move the control lever to raise it.
2) If I turn off the tractor for about 5 minutes, everything functions correctly and strong for about 10 minutes.
3) Running the tractor at about 1750-1800 RPM.
4) There is a faint, intermittent hissing sound (not sure what else to call it) like the sound of a faucet. Is it sucking air?
5) I don't see any fluid leaks.
6) I rechecked the fluid level, and based on the "fluid level overflow plug", it looks to be correct.
7) The bucket and the boom are always 1/2 the speed going down as up.

I'm kind of stuck..

 

[seville009]

Just a guess, but that hissing sound might be a relief valve. I used to hear that on my excavator when I raised the blade; when it got to the top, if I didn’t push down on the lever a bit , it would still try to raise the blade slightly and make a bit of a hissing sound while it was trying.

 

[Banochris]

I'll see if I can locate that valve and see if that's the source of the sound.

 

[Banochris]

Well, I poked around last night. Located the relief valve, inspected the high pressure side, and the intake lines for the hydraulic pump. I didn't find any fluid leeks. I also noticed if the 3-point control was in the middle, like for brush cutting, the 3-point would change position if the FEL was being worked. So I put the 3-point all the way up, and all seems fine. Not sure why that's happening. But then I also deduced my control valve for the Bush Hog 1846QT Front End Loader is not working correctly. I swapped a couple lines around to isolate the problem. and the problem followed the valve ports. So it's definitely the controller. Plenty of bucket power in both directions. The boom is strong lifting, but has ZERO power pushing down. I have a Dukes Fluid Power - 25H43938. Can I rebuild this thing with new seals or is there a replacement that'll do the job?

Monty