John Deere H external hydraulic cylinder

1945 H. My cylinder pours oil out when I try to use it. How hard are they to rebuild? Is there a kit available? Instructions?

Thanks!

Not hard to rebuild as long as the bore is not pitted or grooved, or the rod bent. Assuming the cylinder bore is smooth, there are two things that can make it leak ? the first is the leather cup (#16) which was used instead of o-rings or v-ring seals on the piston. After 70 years of service, those things are possibly worn out or have hardened and won?t seal against the cylinder wall. The second thing is the check valve (#10 thru #15) which is part of a unique oil recovery system.

Deere probably knew this thing was going to leak so they developed this oil recovery system which is comprised of a small piston pump with a check valve. Those check valves have been known to stick open or to be held open by dirt and crud in the system. Oil that leaks past the leather cup collects in the piston grooves and bleeds into a small chamber. When the cylinder is almost fully extended, the plunger (#12) contacts the cylinder head (#6, they call it a Retainer, Piston) and is forced down by the remaining stroke of the cylinder. The leaked oil is thus forced by the plunger back into the cylinder chamber and is held there by the check valve. And keep in mind that for this recovery system to work, the cylinder must be oriented so if it is vertical, the hose inlet is at the bottom, and if horizontal, the two arrows (one cast into the cylinder and the other on the cylinder cover) must be on top. Otherwise, the leaked oil won?t flow down into the recovery chamber and can?t be pumped out. So the idea is that every time the cylinder is fully extended (which is the design intent of the ?H? Power Lift, incidentally), any leaked oil is pumped back into the system.

To disassemble, loosen the setscrew (#2) which permits removal of the cylinder cover and cap (#5). Then unscrew the Piston Retainer (#6). The rest of the disassembly should be apparent. When reassembling, make sure the flat on the end of the cylinder rod flat is aligned with the setscrew in the cover. This is so that the arrow cast into the cover is in the proper orientation for the oil recovery system. When mounted to an implement, those arrows are supposed to point toward each other.

Don?t know if Mother Deere has replacement leather cups, but Sharp?s (and maybe others) offers them.

Thanks Dan! Greatly appreciated!! I am going to attempt to rebuild mine in the near future.

Would any harm come from plugging the output out of the bottom of the pump where the hose attaches? I would like to take this and the hose off when putting around.

You can plug it and as long as the lever is down in the lowered position all is fine. But if the engine is running and someone lifts the lever it can snap up hard and then it will be running against the relief valve which you don't want to do for very long at all.

(quoted from post at 12:40:34 10/16/17) You can plug it and as long as the lever is down in the lowered position all is fine. But if the engine is running and someone lifts the lever it can snap up hard and then it will be running against the relief valve which you don't want to do for very long at all.

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Makes sense, thank you Mike!

You're right, Mike. However, there's an unloading valve in the Power Lift that's supposed to trip open if oil is blowing past the relief valve. So it shouldn't be a problem no matter what someone does with the handle. But if the unloading valve is sticking closed for some reason, or if there's not enough flow rate to trip the unloading valve, the oil will get hot in a hurry. So if the pump is capped off and things are working properly, there would be a moment of oil blowing past the relief when the handle is raised. The unloading valve is supposed sense that rush of oil past the relief valve and should open instantly which would then let oil flow internally under no pressure. There was a field service bulletin that discussed this, and it recommended running the engine fast so there would be adequate flow rate to pop that unloading valve open. Pushing down on the handle will reset (close) the unloading valve as well as lower the implement.