JD 4210, 3pt loses pressure

[DaBender]

I bought a used 2002 JD 4210 last week. It has a 420 bucket that works fine, but the 3pt hitch fails to stay in the up position after a while, and after it droops you can raise and lower it by hand without the tractor running with very little resistance. My father has a model 40 from the early fifties, and the 3pt always stays wherever you leave it.
Any idea what my problem might be?

 

[J_J]

Both neutral and raise should hold the 3pt in a locked position if the system were perfect.

If the piston seals are worn the the 3pt may drop.

 

[DaBender]

Today I was able to determine that it goes into "floppy mode" even with the tractor running. The fluid looks a bit milky in the sight window. A neighbor that does mechanical work thinks a simple change of the fluid and filters might clear it up, but I have my doubts. I've tried contacting the seller, but haven't connected yet.