Partial Failure of curl down

[Dave Pee]

JD 2032r 10 months old, in warranty, but shop is closed today.

Trying to do sand leveling in reverse, with front bucket, pointed straight down; hydraulics do not hold it, and the bucket just curls up.
Can also curl the bucket 1/2 way, by hand; at the 1/2 way point, it stops.

Can load and unload sand from the bucket as normal; curl and un-curl seem fine, no flopping around.

Hoses and connections and cylinders appear fine. Fluid level is fine.

Only scenario that even begins to make any sense, is if one curl cylinder had a pistol failure some time ago, and today the second curl cylinder had a similar type failure.

What do you more experienced folks think??

TIA Dave

 

[Sysop]

Yea, the seals in the cylinders aren't strong enough to support back dragging. All tractor loader manuals specifically state this as an action that will void the warranty. Time to rebuild the cylinders...

 

[Billrog]

Back blading with bucket straight down you can bend the cylinder rods .

 

[rustyshakelford]

Hold it in the curl position till it stops moving. Let off, do it again and hold it. It'll curl and be locked where you want it.

Brett

 

[Dave Pee]

Brett - I don't understand what you are trying to say.

FYI: JD manual says to keep a 40 degree angle when back-blading.

 

[CincyFlyer]

Brett - I don't understand what you are trying to say.

FYI: JD manual says to keep a 40 degree angle when back-blading.

With that kind of angle, and the lift arm in "float" mode, you'll avoid any high pressures in the bucket cylinders as the bucket follows the earth's contours. Straight down at 90° you could over pressure a hose if you hit one of the the innumerable immovable objects found in the earth. Heck, my bucket free-falls at that sort of angle (assuming a valve issue, don't care 'cuz I'm replacing the valve).

 

[LD1]

Not going to argue about weather one should back drag, and how it should be done. MAny people do it all the time and no issue. Some have issues bending rods and popping hoses.

But none of that is relevant to why the bucket wont hold position. Piston/seals have nothing to do with weather the loader will hold position when back dragging. Because you are trying to compress the cylinder. And the ONLY way for that to happen is either you have air in the cylinder, or oil is leaving the cylinder.

Well, if there are no leaks, and you joystick valve centered....the oil aint leaving. So that only leaves air in the cylinder..

And thats actually a common problem on the curl circuit if the valve doesnt have regen. (or if you arent dumping using the regen function) dont know which applies to you/tractor

Basically what is happening is when dumping the loader, (especially at idle and/or with a load) is gravity is dumping the bucket FASTER than it can be filled with new oil. This results in a cylinder half full of oil, half full of air. Air compresses, oil dont. Thats why it only wont hold, up to a point then will feel rock solid. Because you compressed all the air, and now pushing on the oil.

How to prevent this......

IF your valve has regen....use it to dump. (some valves have two functions when dumping that you have to push past the detent. Sorta like lowering the loader....then pushing past that detent into float)

IF your loader dont have that, dump the loader ALL the way til it hits the stops. Then hold the lever there for a few seconds to purge all the air out. THEN curl back to whatever backdrag angle you want.

Nothing wrong with the tractor IMO, and I wouldnt waste the dealers time til you at least try that.

 

[Dave Pee]

LD - you may be right about air in cylinders. I tested it this morning, and cycled it a couple of times - seems like the play is now just one inch or so (of the bucket).

I will double check, but i don't think I have a regen feature.

Thanks to all!
Dave

 

[LD1]

LD - you may be right about air in cylinders. I tested it this morning, and cycled it a couple of times - seems like the play is now just one inch or so (of the bucket).

I will double check, but i don't think I have a regen feature.

Thanks to all!
Dave

Its a common issue on loaders that dont have regen, or operators not using that function

 

[rustyshakelford]

It's not air in the cylinder. All my deeres have done this. Get the bucket where you want it but put some pressure on it. Let off the loader control valve. If you start back dragging, it'll curl up right? Get back on the curl and hold it to curl it down. You'll feel it start to move the tractor. When it'll support the tractor your good to go. I can send you my number and walk you thru it. I'm not doing a good job articulating it but it's very simple. When it stops curling back, stop and do it again. It'll be good to go.

Brett

 

[CincyFlyer]

It's not air in the cylinder. All my deeres have done this. Get the bucket where you want it but put some pressure on it. Let off the loader control valve. If you start back dragging, it'll curl up right? Get back on the curl and hold it to curl it down. You'll feel it start to move the tractor. When it'll support the tractor your good to go. I can send you my number and walk you thru it. I'm not doing a good job articulating it but it's very simple. When it stops curling back, stop and do it again. It'll be good to go.

Brett

Yep, it literally cannot be air, or you'd see a bunch of hydraulic fluid all over the place. My bucket sometimes "free falls", and I want to investigate why.

 

[LD1]

It's not air in the cylinder. All my deeres have done this. Get the bucket where you want it but put some pressure on it. Let off the loader control valve. If you start back dragging, it'll curl up right? Get back on the curl and hold it to curl it down. You'll feel it start to move the tractor. When it'll support the tractor your good to go. I can send you my number and walk you thru it. I'm not doing a good job articulating it but it's very simple. When it stops curling back, stop and do it again. It'll be good to go.

Brett

Thats air in the cylinder. No ifs ands or buts. IF the fluid aint leaking out, and the cylinder is still compressing....air is the ONLY possibility. Cause a cylinder full of fluid aint gonna compress.

What you describe, by putting it where you want it, hold it into the ground and stay on the curl til it moves the tractor.....you are purging the air out. Same thing I described by just dumping all the way to the stops and holding it for a few seconds longer. Something has to PHYSICALLY stop the loader from moving. Otherwise its just the air in the cylinder compressing a little bit and moving the loader just like an air cylinder would.

With the bucket physically stopped, the air compresses SO much that its purged out of the cylinder.

 

[LD1]

Yep, it literally cannot be air, or you'd see a bunch of hydraulic fluid all over the place. My bucket sometimes "free falls", and I want to investigate why.

Why would you say its not air. Why do you assume that if there is air in the system that their would be hydraulic fluid all over?

 

[rustyshakelford]

I have 70 hrs on this tractor. Prolly 350-400 on the other ones and they all have done this. It's something with the loader control. Air would be purged out long ago. You have to do this every time you reset the bucket. It's a Deere thing. Wish I knew how to explain it better. Once you know what to do, it's second nature. Something about the curl??? I'm obviously making the explanation sound like it's a in depth thing. Really only take a few seconds to get it going. I'll be home wed morning and will try and take a video

Brett

 

[LD1]

I have 70 hrs on this tractor. Prolly 350-400 on the other ones and they all have done this. It's something with the loader control. Air would be purged out long ago. You have to do this every time you reset the bucket. It's a Deere thing. Wish I knew how to explain it better. Once you know what to do, it's second nature. Something about the curl??? I'm obviously making the explanation sound like it's a in depth thing. Really only take a few seconds to get it going. I'll be home wed morning and will try and take a video

Brett

Everytime you dump, gravity is dumping the bucket faster than it can fill with oil. This sucks air in EVERY time.

ITs not about purging air out from new. Yes its an every time thing. A regen valve would solve that problem. But yes, its air

 

[oldnslo]

LD1 is correct, there is air in the system.

Some people have installed a orifice in the rod end line of the curl cylinders. Correctly sized this reduces the "freefall" and prevents the vacuum / air from entering the blind end of the cylinder.

I installed a counterbalance valve on my Branson since the Counterbalance valve operates on pressure it works under all dumping speeds and conditions.

 

[LD1]

Hydraulics aint rocket science.

Counterbalance valves are used in alot of industrial applications, like large vertical presses. Prevents gravity from wanting to pull down faster than fluid can enter.

Dont know why everyone always things the physics of these things changes magically when you start talking about tractors. Its hydraulics 101.

To illustrate the point.......have you ever used one of them lever action barrel pumps???

Notice how if you go slow and steady that you get alot of flow with each cycle. But if you try to cycle as fast as you can, how each cycle is only pumping out about half of full volume? Especially on an older wore out pump?

Thats because you are physically moving the piston inside the pump faster than it can fill with fluid. Creating an air pocket and that "squishy" feel. And you are only pumping the amount that could enter in the short time.

Same thing with curl. Gravity is physically actuating they cylinder/piston faster than fluid can enter.

Regen would solve this
Counter balance would solve this
A restrictor or flow control on the rod side would solve this
Or just dumping the bucket against a hard stop (edge into the ground or full dump against mechanical stops) and give it a few seconds to purge/fill would solve this.