656 Hydraulic Pressure Check

[JerryF]

Couple of months ago my Koyker loader on my Farmall 656 lost most of it's hydraulic power. I replaced a few hoses which were seeping a little and also the oil cooler bypass hose behind the battery, which had ruptured. Assuming that the problem was either the pump or the rilot relief, I changed out the pilot relief first with a new 2000# unit as I wanted the additional capability anyway. This did nothing so I took out the pump and noticed that it was worn pretty bad inside, so I got a rebuilt one. Still weak lifting, but tilt seemed to work better.
Now I'm lost, so I checked aux outlet pressure, and each easily go 2000#, but then slowly (over a few minues) loose all pressure. I thought that there were check valves on the bottom of the control valves - but I have a hard time believing that all 4 are bad and seem to leak about the same rate. Are those 4 valves suppose to hold pressure or could have the larger pilot valve damaged them? Or, am I all wrong in my thinking and is there a different check valve upstream, maybe in the steering wheel flow control valve?

thanks,
Jerry

 

[Allan in NE]

Jer,

Not trying to be a smart-mouth, but you replaced the right pump, didn't you? The front one?

How about that balance valve down there at your right boot heel. That isn't stuck or leaking across to the other side is it?

Sure sounds like it's going into full system pressure then losing it at a massive leak somewhere.

Does the hitch work normal in and of itself?

Allan

 

[JerryF]

Yes, the front one. I did use a rebuilt 17Gal Cessna instead of the Thompson that was in there. But, they are equivalent.

What is a balance valve?

Even though the outlets are loosing pressure over time, I think I found the main problem. The seals in the piston on one of the loader cylinders is blown out, creating equal pressure on both sides, hence only letting one cylinder work.

Hitch works great. Can sit a bale on it for a week and wont go down a bit.

Thanks,
Jerry

 

[Allan in NE]

Oh yeah,

That would do it. :>)

Aren't those 17 gal pumps just the cat's whiskers? Can't get over the oil that they'll throw. Nice part is they just about fit any tractor too. :>)

Let's see, how does that go now? On high demand and IF the hitch isn't being used, that little shuttle thingy will let the back pump "help" the front pump. But, it doesn't work the other way around?

Dunno, maybe I have that backwards.

Anyway, it is called "full sytem pressure" and one of the pumps will help the other unless it is busy doing it's own chores.

Allan

 

[TractormanNC]

As it came from factory, 656 main hyd system (front pump) had a 1600 psi relief valve and the hitch (rear pump) had a 2000 psi relief valve. Under these conditions, I can see how the hitch pump could "help" the main pump. But with a 2000 psi relief on both systems I dunno bout dat???

 

[TX656]

JerryF, I'm fighting the same problem with a Koyker on a 656.

Standing and looking at the tractor/loader from the say the right (shifter/loader valve side) where is this seal located? Top of the cylinder or bottom or neither? How did you verify yours had failed? Thanks for any clues.

 

[JerryF]

The piston is located inside the cylinder. The way I checked it (not saying it's the proper way) is I retracted the cylinder all the way, then unhooked the lines on the bottom of the cylinder. Tried to retract some more and the side with bad piston seals had oil pouring out. The good side may leak a little, but just a couple ounces and then quit. Koyker has a good website and links to owners manuals on how repair the piston seals. Now just have to wait until Monday when the dealer opens to get them.
Koyker Loader Page

 

[044GTO]

Happy days are here again! I replaced the piston and gland seals on the loader cylinders, and WOW! Lifts heavier loads than ever now with the nearly fully rebuilt hyd system. Only sorry I waited so long to do it.