Bucket has a mind of it’s own

[JwrightD]

I have a late 1980’s John Deere 750, recently the bucket hydraulic’s has had a mind of its own. No matter what I do whether it’s tipping the bucket or trying to lower it just keeps wanting to go up. And then all of a sudden it will go down but it’s after shifting the levers back and forth in all directions. If I leave the tractor running for a few minutes to do something, when I come back the bucket has slowly gone all the way up. You can hear the hydraulic’s leaking by when the bucket is moving slowly on its own and sometimes when I shake the levers back and forth (horizontally) I can get it to stop. I’m thinking it must be the hydraulic control unit but I’m not sure. Has anyone had this issue and if so what did you do to fix it? If it is the hydraulic unit I’m hoping I can just rebuild it?
Thanks

 

[BackRoad]

Surprised nobody has commented yet. There are some smart guys on here that do this for a living.

My guess is symptoms seem to point at the lift valve which you point out.

Might be something foreign holding it open, stuck valve, or worn valve?

Below was my experience in isolating and resolving a valve issue with very limited experience working with hydraulics...

My symptoms were the lift wanting to go down (not up), with the root cause being a valve not returning to a closed position (it continued to let flow hydraulic fluid flow). Potentially the reverse of your lift wanting to constantly go up.

My spindle assembly was easy to take apart and reassemble.

You may get some ideas from reading through the thread to help troubleshoot yours.

MX6000 - FEL and 3PH Stopped Working

2020 Kubota MX6000, HST, 1070 hrs, with FEL, plus 3 Remotes and Fit Rite TnT added 2 years ago: Using the grapple today and lost the ability for the top section of the grapple to stay open. It would open up as long as the open valve button was actuated, then it would gravity close in 2-3...

www.tractorbynet.com

 

[JwrightD]

Surprised nobody has commented yet. There are some smart guys on here that do this for a living.

My guess is symptoms seem to point at the lift valve which you point out.

Might be something foreign holding it open, stuck valve, or worn valve?

Below was my experience in isolating and resolving a valve issue with very limited experience working with hydraulics...

My symptoms were the lift wanting to go down (not up), with the root cause being a valve not returning to a closed position (it continued to let flow hydraulic fluid flow). Potentially the reverse of your lift wanting to constantly go up.

My spindle assembly was easy to take apart and reassemble.

You may get some ideas from reading through the thread to help troubleshoot yours.

MX6000 - FEL and 3PH Stopped Working

2020 Kubota MX6000, HST, 1070 hrs, with FEL, plus 3 Remotes and Fit Rite TnT added 2 years ago: Using the grapple today and lost the ability for the top section of the grapple to stay open. It would open up as long as the open valve button was actuated, then it would gravity close in 2-3...

www.tractorbynet.com

Thank you, really appreciate it!

 

[Harry in Ky]

You say the "bucket" is the part with the problem. Assuming that's the bucket/tilt circuit, and the boom up/down circuit works just fine? Also assuming then, you have tried swapping the lift and curl circuits between valve spools just for effect and found what? The same thing occurs with that spool regardless of what cylinders are connected?

What's the history of the problem? Nothing has been changed or worked on recently in regard to hydraulics?

I can see six fittings on the valve pictured. Is there another one out of sight? The other hydraulic component on the loader frame. What is that?

 

[JwrightD]

No, both circuits are whacky, there’s really no rhyme to reason, it mostly wants to go up when I’m trying to tip the bucket to dump it. It seems like the majority of the time the bucket wants to go up or down when I’m trying to use the tilt lever and it seems to be getting worse and the bucket constantly wants to go up on its own even if the tractor is just sitting idling. There is another fitting that you couldn’t see in those pictures, I’ll attach a few more so you can see. I have not tried swapping the lift and tilt lines, I didn’t know you could do that. There is a backhoe on the back which has lines that run back to it and to something under the seat.
Thanks for taking the time to help out with this!

 

[Harry in Ky]

Usually when someone has problems with either the lift or curl functions and wants to determine if the valve is part (or all) of the problem they can set the loader down, shut the engine off, then work both levers back and forth a few times. When everything stops moving, unplug the couplers for the lift circuit and swap them with those on the curl function. Just trading levers for each function. DON'T cross them. Keep the lift hoses as a pair and the curl hoses as another pair. If you cross them it can drive you crazy trying to sort it back out, even if you THINK you have them all clearly marked.

Now if both functions are acting screwy, then it's not just one bad valve spool circuit. In theory, the backhoe circuits would have nothing to do with this, but you can't count on that. Has anything regarding the hoe circuits (or any other circuits on the tractor) been worked on or changed just prior to this starting? Or has this just been ongoing and getting worse over time? My first thought is you probably need a new loader valve, but I would need to know more before condemning anything.

 

[JwrightD]

Okay, I’ll give it a shot and switch the hoses over(probably won’t get to it until this weekend). I added the backhoe about 4 years ago, other than that no work has been done to it. I feel like this issue started well after that, maybe the last year, definitely less than a couple of years. I didn’t think much of it at first cause it would only do it once in a while, I actually thought it might be a piece of dirt in the valve and was hoping it would work its way out. But it’s now gotten to the point where you literally have no control over the bucket. Do you know if those control valves are rebuildable (o ring kit) or do you usually have to replace the whole valve?
Thanks again for your help!

 

[Harry in Ky]

From what I see in the photos, that valve is probably well past it's prime, but in any case spool valves are not effectively "rebuildable". Just look for a ten GPM loader valve and plan to swap it out. Those valves are easy to find and pretty cheap in most cases.

 

[Harry in Ky]

One more thing that comes to mind. You stated there is another fitting somewhere on the valve. The two ports I can see in one photo are marked in and out. Is the the third port marked as well? If so with what? I'm wondering if it's BYD or something similar. I see three hard lines in one photo, two of which have hoses connected to ports back near the lift housing and one to a fitting (presumably to transmission case?). I'm wondering if there may be some restriction in the flow through the rear hydraulics that may be causing the problem with the loader valve. It's a long shot, but maybe worth looking at. Before condemning the valve, I would consider first removing the hose going into the port on the back. Whichever hose that is that comes from the valve port not labeled "in". In theory, that should be the power beyond line carrying fluid back into the rear hydraulics. Remove that line from the fitting, cap the port it came from. Jury rig an extension of sorts and direct that flow back into the tractor eliminating everything beyond that port from receiving any oil flow from the pump. Then try the loader valve again and see if anything changes. That will effectively narrow down the problem (if it still exists) to the loader valve.

 

[JwrightD]

From what I see in the photos, that valve is probably well past it's prime, but in any case spool valves are not effectively "rebuildable". Just look for a ten GPM loader valve and plan to swap it out. Those valves are easy to find and pretty cheap in most cases.

Oh good, glad to hear. I went onto the John Deere website and they want close to $2200 for one! I’ll search else where. Thanks!