JD310G - Drooping dipperstick

[MontanaSteve]

I've got a 2001 or 2002 JD 310G that we recently purchased. If you've got the boom extended, the dipperstick will slowly droop down after a couple minutes. There are no obvious seal or hose leaks. Any advice on what could be the issue causing the hydraulics on the dipperstick to slowly drop?

Thanks for your knowledge and assistance.

 

[Welder Dave]

Most common reason is piston seals on the cylinder or maybe a loose piston nut/bolt but that's not too common. . Because it's in the cylinder it won't leak fluid that you can see.

 

[MontanaSteve]

I was hoping someone would have some idea that didn't include rebuilding the cylinder. :-\ Thanks for the input.

 

[Delmer]

Have you looked up the spec for how much is normal, or tolerable? Ir's not supposed to hold forever.

 

[MontanaSteve]

I have not, but know it's way beyond normal. As soon as you let off the stick, it starts creeping down right away. Pops down in little increments.

 

[NH575E]

That's a lot of weight. If the piston seals are flat like all the others I've seen I wouldn't expect it to hold long. Mine creeps down if left in one position for a couple of minutes. It won't fall to the ground real fast but if I left it without the lock on it would probably be sitting on the ground in a few hours.

 

[Billrog]

Certainly sounds like piston seals.

 

[ol'stonebreaker]

Probably leaking back through the control valve.
Mike

 

[Billrog]

I'm not familiar with JD control valves but the main boom on my Case would slowly drift down after putting up with it for a few wks. I started at the valve bank and found the cap on the bottom of the control valve for the boom was loose. Hand tightened it and that was the end of the problem. This was a few years ago still holds all day. I have no idea of the relationship but it worked.

 

[ol'stonebreaker]

Many years ago I attended a hydraulics class while an IUOE apprentice. The instructor put up a drawing of a double action cyl full of oil with both ports plugged and a hole through the piston. He posed the question of whether the piston would move either direction with force applied to the rod. The answer was no, it will not due to the difference in displacement because of the presence of the rod on one side.
Mike

 

[John C.]

There is usually a spec somewhere denoting drift in inches per minute. Generally I considered them unsafe if they drifted down more than three to five inches in a minute. It's just a backhoe. How expensive and difficult could it be to replace the packing?

 

[MontanaSteve]

There is usually a spec somewhere denoting drift in inches per minute. Generally I considered them unsafe if they drifted down more than three to five inches in a minute. It's just a backhoe. How expensive and difficult could it be to replace the packing?

It's definitely drifting down more than that. Not saying it's expensive or difficult, just wanted to know if there was some other common issue that might cause it or something. Just need to get the kit and spend the time to repack the cylinder.

Thanks for everyone's insight.

 

[GregsHD]

You can verify its leaking by the piston seals.

Lay the boom on the ground, stick out, relieve pressure and mark/plug/cap the lines going to the stick cyl, raise boom and see if it drifts the same. Could be the stick (out) relief cartridge leaking.

 

[MontanaSteve]

You can verify its leaking by the piston seals.

Lay the boom on the ground, stick out, relieve pressure and mark/plug/cap the lines going to the stick cyl, raise boom and see if it drifts the same. Could be the stick (out) relief cartridge leaking.

Thanks for the tip Gregs. I will definitely give that a try to narrow it down so as to not do unnecessary work. Appreciate the tip.