851 3 point wont lift

The three point quit working today. I had quite a good weight on the back, about 1500 lbs. Is this to much? I need it for picking up the big square bales. How hard is this to fix? I was reading the sevice book and it says to replace the o-rings? Has anyone done this? Is it a pretty easy job? Thanks in advance. Rob

I too had this problem on my 850, and I found the problem to be in the valving. But I would say first check out that the pump is working and you have flow. If you have good flow it is probly the unloader valve underneath the cover. It is stuck, that was what was wrong with mine. the cover comes of easy and the unit comes apart just as easy. It is pretty self evident how it comes apart. There is one plug you have to pull it has 1/2 fine threads and comes out with a slide hammer.

determine that you have flow.. then make sure you didn't blow the piston / oring and have a massive leak there.. past that.. could be unload valve or relief valve.

in general.. if the lift will pick it up.. it should be ok.. though shock loads may make the relief pop.

soundguy

Rob:

The failure could be caused by a variety of problems.

Does your tractor have remotes? If so do they work?

I would start by removing the hydraulic filler plug and looking inside for leaks with a flashlight and dental mirror. If you see oil draining from the open end of the cylinder the piston O-ring/back-up washer is the most likely culprit.

Possible, though less likely is a broken piston. It is possible for the dog bone to break through the piston crown allowing oil to flow through the piston. This is often caused by lifting a very heavy load. Detatch the implement from the lift allowing the lift arms to lower fully to the bottom of travel. If the lift will now raise, it is likely that this is the problem.

It is also possible, (though unlikely) for the safety valve (not the relief valve), which rarely opens, to open and fail to reseat if you have driven the tractor over rough terrain with a very heavy load on the lift. If this is the problem, you should see oil flowing down from the area of the hydraulic accessory cover plate. Note: The safety valve can be accessed by removing the accessory plate (or remote hydraulic valve) without removing the lift cover.

Of course, it is also possible that internal O-rings or even weak corroded spots in the through-transmission steel hydraulic lines have perforated. Is the oil level in the hydraulic sump and transmission at the proper level?

Dean

Dean, I did have a pretty heavy counterweight on the three point, and was over some pretty rough terrain. Also, it was leaking on the right front corner of the cover (if you were sitting on the seat looking down, could this be the safety valve? Thanks guys for all the help. Rob

Probably not. The right front cover is where the O-rings for the internal oil passages are. Perhaps you need new O-rings. I recommend genuine CNH O-rings rather than generic equivalents.

Dean