Falling 3-point hydraulics

[bigcountry1009]

The three point hitch on my Farm Pro 2420 won't stay up. It raises fine, just won't hold my mower up. I replaced the seals in the lift assembly but that didn't help. I have power steering that's working great, so I don't think it is the pump. Now I'm thinking about replacing the lift piston and cylinder or replacing the lift valve assembly. I've already taken it apart an haven't found any real issue with it. Anyone have any other ideas??

 

[Bobvt]

The first place I'd check is the rings on the lift cylinder. If the draft arms stay up while the tractor is running, but fall after the tractor is shut down, oil is likely leaking by the rings.

Bob

 

[bigcountry1009]

Well, I've changed the seals already and it didn't even slow it down, so the hunt is still on.

 

[JC-jetro]

Well, I've changed the seals already and it didn't even slow it down, so the hunt is still on.

I have relief on my lift cylinder, if the relief stays stuck open the pump has still enough flow to lift but it leaks back to the reservoir. There also may be a check valve from the discharge of the spool valve to the lift cylinder, that could leak the flow back to reservoir only if the spool is leaking by. you most probably have a rate of drop knob for your lift system right below your seat. That is a needle valve and if you close it you will block the leakage back to reservoir. If you close it and the arms drop most likely your lift cylinder is leaking by the new seal. It may have been damaged during repair.

JC,

 

[Soundguy]

Any way you can look into the oil sump and look for squirts and leaks.. like fromt he mouth of the cyl.. or from a relief valve?

soundguy

 

[RonMar]

Well if you have replaced the piston seals, and are sure they are OK, then you either have a crack in the cylinder or piston venting fluid, or a problem with the lift valve. I think your Farm Pro is a rebaged Jinma. If it is, then one thing you might try to help determine which it is, depending on exactly how your lift is configured, is to raise the impliment in the air, then fully close(clockwise) the speed regulating valve in front of the seat. In many cases this valve can be fully closed and completely isolate the 3PH cylinder from the lift valve. If the impliment stays in the air once this valve is screwed closed, then the issue is in the lift valve assembly.

Locking a load in the air with the speed reg knob can hydrauically lock that valve knob in place and you will not be able to unscrew it to lower the impliment due to the weight of the impliment pressurizing the system. Mine(jinma 284) does this and I either need to jack up the impliment or back it into a rise and take all the weight off the 3PH to unscrew the valve knob. Once the weight is off, it unscrews with 2 fingers. With the weight on, you can't move it with a pipe wrench.

If yours is a Jinma, it may be that the 3PH overload safety is in the lift valve assembly(mine is), and as mentioned, it may have something keeping it open slightly and allowing the fluid to escape from the 3PH.

Does your 3PH valve look like this?
http://johnstractor.homestead.com/files/HydValve.jpg

If so, the safety valve in question is comprised of parts 1-7 and is easilly accessed by loosening the square headed plug(part #1) and lifting the parts out for inspection.

 

[bigcountry1009]

Yes sir, the Farm Pro's are rebagged Jinma's. And my paper work is the same. You have given me some other things to look at, thanks man.