Bucket droop

[Evets Tsorf]

There are a gaggle of posts about this somewhere here but I did not find it.

Noted my new to me JD750 bucket dropping while brush hogging after parking noted fluid leak at left boom lift cylinder. Removed it and brought it to my shop and resealed it and reinstalled. Drained fluid, cleaned filter and cycled system, bucket and curl both sag, no external leaks, system weak will not lift front of tractor.

Next step, rebuild other three cylinders, or go after control valve? Thoughts?

The new actuator looked so good with new paint I spent the rest of the weekend painting the whole FEL

 

[arlen4720]

Probably the first thing to do is get a pressure gauge and start checking pressures to see why the loader is weak. How much is it drooping in say 5 minutes?

 

[Evets Tsorf]

Mr.4720, Drop significant. will drop a couple feet in five minutes. May consider putting a heavy load in bucket, raise bucket and shut off tractor and see if I can hear internal leakage with a stethoscope.

The rebuild kit I received from JD had a really hard seal for the inner piston, I struggled getting this in place as it was so stiff, it had an "o"ring in the back of the seal that kept popping out. We where able to message it back in place, hope it did not get cut in process.



That is Mount Lassen in back ground.

 

[3Lfarms]

I grew up in Palo Cedro. Looks like quite a bit of snow on Lassen for mid June.

 

[Evets Tsorf]

Yes and Shasta is really covered, all got a fresh dusting in mid May that also covered the west hills and Trinity Alps, should keep lakes full this summer.

Congratulations on growing up, where you hanging out with Merle.

 

[3Lfarms]

Never met him personally. I used to admire his houseboat on Shasta lake though. Good times.

 

[Evets Tsorf]

Not seeing much in the way of ideas here. After thinking about this for a bit I am leaning towards the hydraulic pressure relief valve as it could cause all three issues seen, drooping bucket lift cylinders, drooping curl cylinders and weak hydraulic pressure. I do not know if the thee point is drooping as well as I did not have a load on it when noting the issue. Unfortunately all may service info is at my house up north with the tractor. Does anyone know where the hydraulic relief valve lives on the 650/750 tractors?

 

[beenthere]

Have the service manual for the 670 and 770 tractors.. can look there if you think they may be similar..

 

[Evets Tsorf]

Beenthere,

Not to worry, I can check my manuals tomorrow when I go for my conjugal visit with the tractor.

So far I have just called my tractor John, as it is on the tractor and sounds fairly strong though I keep walking past a plant at my house in the Santa Cruz mountains that always reminds me of John Deere, do you think Dahlia is a bit to feminine as a tractor name ?

https://www.tractorbynet.com/forums/images/attach/jpg.gif

 

[Dave M7040]

Not seeing much in the way of ideas here. After thinking about this for a bit I am leaning towards the hydraulic pressure relief valve as it could cause all three issues seen, drooping bucket lift cylinders, drooping curl cylinders and weak hydraulic pressure. I do not know if the thee point is drooping as well as I did not have a load on it when noting the issue. Unfortunately all may service info is at my house up north with the tractor. Does anyone know where the hydraulic relief valve lives on the 650/750 tractors?

The relief valve in the loader valve is not in the loader circuit when the loader controls are in the middle or neutral position so it is not going to be the cause of all your issues. Same for the main relief valve.

I have posted a procedure for checking the double acting cylinders which others have found helpful.

Rule out the bucket control valve by swapping lift arm hoses for bucket hoses. If the problem remains with the bucket drooping, then the problem is not in the valve.

Dave M7040

 

[Evets Tsorf]

Dave thank you, not having a pocket full of caps and plugs I assume this check could be done by simply disconnecting quick disconnects at control valve. Would not isolate individual actuators but could rule out supply side issues from actuator issues.

 

[Dave M7040]

I am not certain you can perfom all tests just disconnecting quick connects as some tests require one of a cylinder's ports to be open.

It is rare for a control valve to cause these problems. They have no internal seals being manufactured to such tight tolerances between the spools and the valve body that no leakage occurs.

Dave m7040

 

[dapeake]

Steve, Did you ever figure this out? I have a JD 650 with a model 67 loader and my bucket sags too.

Dan
Campbell / San Jose (Right over the hill from you!)

 

[art]

Loosen the hoses on the cylinder on the dump side and see if they are leaking by while the bucket is rolled back. Simplest way to find out if it is the cylinders.

 

[Evets Tsorf]

Dapeake,

Have not had that much seat time recently other house projects got in the way. I had changed fluid and cleaned the fliter, also rebuilt left bucket lift cylinder, the last time I drove it the droop seemed decreased, may have had some air in system. Unfortunately I noted the cylinder I just resealed is dripping again, had a heck of a time getting the main seal (polypack) in place it was just to inflexible. Did get it in but the o ring kept popping out of the seal when trying to wrestle it in place. Got it stuffed back in place but may have cut the o ring.

Would love to see your 650 if it has ROP's, I acquired a 650 Bar and am trying to understand how it attaches. There is a difference between the 650 and 750, but not being able to find a 750 bar I felt I could modify the 650 unit as most dimensions are the same they just mount differently. I my office is at the San Jose airport and I drive through Campbell every day. PM me and maybe we can get together.

 

[Cperk]

Mr.4720, Drop significant. will drop a couple feet in five minutes. May consider putting a heavy load in bucket, raise bucket and shut off tractor and see if I can hear internal leakage with a stethoscope.

The rebuild kit I received from JD had a really hard seal for the inner piston, I struggled getting this in place as it was so stiff, it had an "o"ring in the back of the seal that kept popping out. We where able to message it back in place, hope it did not get cut in process.

View attachment 608582

That is Mount Lassen in back ground.

Beautiful view!