Did I bust something on the loader hydraulics?

[ljjhouser]

Does it do the same thing when it is running?

 

[npalen]

If the bucket not being level had anything to do with the hydraulic fluid system it would have gone away just by hitting top and bottom of lift travel a couple of times. Something is bent or shifted on that one. The fact that it goes level at the top and bottom is just the loader hydraulics flexing it back the other way, but not flexing it past its 'yield strength', so when you release it just springs back to 'bent'. With careful setup you might be able to use the loader hydraulics to 'unbend' it just like people do with their SSQA cross-tubes.

The bucket rocking so easily while the valve is in the 'neutral'/middle position likewise COULD be air but that should have rectified itself just by fully extending and retracting the cylinders several times. What makes me think it still IS air in spite of that theory, is how easily it moves. Even if a piston seal or a spool valve leaked, you still have to 'pump' fluid through that 'orifice' to get the cylinder to move, and basically ALL of the fluid in that circuit has to move to do it. Even without much restriction from the leak/orifice, it's still a fair amount of inertia and more like stirring honey than just flopping around like in that video. If you consider something like leaving the bucket tipped down a little, putting the loader in float and letting it hit the ground, turn off the tractor, and then pull the bucket curl valve, the bucket will 'settle' to the ground much slower than the movement shown in that video, and that's with the valve fully open with the whole weight of the loader and part of the weight of the bucket on it, not just something 'leaking' with one measly boot pushing down on it. The system has a LOT of air in it!

As for how the air got in there and then.. never left or never stopped reappearing, i'd be especially suspicious of shaft seals on the cylinder glands, valve body handles/levers or at the pump. A lot of hydraulic pressure seals are directional lip seals, which means their ability to seal goes up with the pressure pushing them against the shaft, and down when that pressure goes down. They're also bad at resisting any pressure from the 'outside', which is usually just atmospheric pressure so not usually a problem.

But think of this. This loader works when the tractor runs. When you pressurize circuits, it more or less becomes normal. Once you fully relieve the system pressure, it becomes wonky and may only do so after sitting for a while. My theory is that a directional lip seal is now allowing air to suck into the system when the pressure drops to 0, but then seals again as soon as you MAKE pressure in the system. I have seen something similar to this on leaky cylinder gland seals, as im sure many others have. They seal 'better' when retracting the cylinder because pressure is forcing them against the rod, but leak profusely upon extension because no real pressure builds in that chamber when the control valve is open on that side.

Just because hydraulic pressure drops to 0 doesn't mean there's nothing to generate 'suction' in the hydraulic system. The weight of any hydraulic fluid being held above the sump that has a free path to flow back to the sump is only being held in the lines by the ability of the system to keep air out of shaft seals. If you picture sticking a straw in a drink, covering the end with your finger and picking up the straw, the liquid only stays in the straw because your finger is sealing against that 'suction'. So my perhaps left field theory is that you might have damaged a directional lip seal which is allowing the weight of the fluid held above the sump to suck air into the system every time the system pressure drops to 0. The loader itself never moves because it's already on the ground, only the fluid in the system moves as some migrates back to the sump and is replaced with air. Once you start the tractor, the pressure causes damaged seal to seal again, and loader will more or less immediately work, although you might notice its initial response to the first lever inputs is delayed (squeezing the air pockets before making real pressure), and its ability to hold weight is 'springy' (air spring) until you've chased all that air back to the reservoir and purged it, at which point it becomes 'solid' again. Until it's parked for a while!

You make some good points about how air gets into a "sealed hydraulic system" including how air can get past a unidirectional seal.

I'll mention again the scenario of dropping the loader and/or bucket quickly, especially with a heavy load on it, where the pump can't keep up with the volume of fluid needed to fill the rapidly extending or retracting of the bucket and/or lift cylinders.

There is a lot of vacuum created in the "other side" of the cylinders during the "drop" and that vacuum is probably sucking air past the seals and/or the pump.

Brian (FitRiteHydraulics MtnViewRanch) has mentioned, on occasion, cycling the 3PH top link cylinder slowly when purging air so that the pump can keep up with 3PH load trying to overrun the pump. Same principals apply here.

 

[Zebrafive]

I've had 3 tractors and when the bucket is sitting on the ground with the front edge up a bit they all did exactly the same thing when you stepped on it . There is no resistance because the controls are in neutral and the fluid is able to flow with no resistance.

It could be play in the pins, linkage, that lets the bucket rock. Or if the hydraulic fluid cooled from when the tractor was parked, the fluid might have contracted enough for some "hydralic play" too?
On the original post, I guessing twisted the loader frame or a mount moved, if not tight enough bolts holding it.

 

[Tx Jim]

npalen
Would performing what I previously stated in my previous reply(#8)[/quote]I'll suggest to raise FEL boom then curl/retract bucket several times utilizing tractor hyd system.[/quote] accomplish what Brian(FitRiteHydraulics MtnViewRanch) stated & accomplish this task?









[

 

[Tx Jim]

Well I must eat crow after Tx Jim set me straight i knew he was correct. I thought I'd better check again stepped on the bucket rocked it and sure as hell it looked like the cylinder rods moved an " or so. I knew it wasn't possible so i looked real closely where the rod came out and sure a heck it never moved. Rocking it back and forth I realized the edge of the bucket reflection on the chrome rods going up and down gave the impression they were moving. Thank you for the common sense post Jim.

You're Welcome.
Another possibility I mentioned earlier is nut holding bucket cylinder piston on rod stripped the threads & piston is loose on cylinder. I think one or both bucket cylinder piston seals needs to be visually inspected.

 

[rScotty]

Usually via the pump.

Edit: Also, on a loader with a lot of weight and letting the it down quickly and then closing the valve. The pump can't keep up.

Both right. You'll get air entrained into the hydraulics fluid from any air leak in the suction side. Then on the pressure side any movement that results in a sudden drop in fluid pressure allows the entrained air to form air pockets. The air will eventually clear up when the oil heats up and circulates a few times.

 

[Vigo327]

Brian (FitRiteHydraulics MtnViewRanch) has mentioned, on occasion, cycling the 3PH top link cylinder slowly when purging air so that the pump can keep up with 3PH load trying to overrun the pump. Same principals apply here.

I have an electro-hydraulic top link and i have to set the implement to the ground before extending that cylinder to keep the pump (which is on the cylinder) from getting unhappy.



Regarding the OP's situation, i dont think the air got in there ONLY during the actual incident because it would have cleared up just by running the cylinders in and out enough. I suspect it is also getting air in while sitting still. But glad to hear of some other possibilities here to add to my 'diagnostic repertoire'.

 

[npalen]

npalen
Would performing what I previously stated in my previous reply(#8)

I'll suggest to raise FEL boom then curl/retract bucket several times utilizing tractor hyd system.[/quote] accomplish what Brian(FitRiteHydraulics MtnViewRanch) stated & accomplish this task?









[
[/QUOTE]
Yes, but must be done slowly and repeated several times especially when dropping the boom.
Also, I don't think the air in the system has anything to do with the log in grapple incident.

 

[Tx Jim]

Has it been established(VERIFIED) that any air is in JCoastie's FEL hyd system & I OVERLOOKED that FACT? Thread originated about bucket control circuit not boom circuit.

 

[DieselBound]

Shouldn't ever take much time to get air worked out. Work it well and it'll purge pretty quickly: think "GPM."

It was an EVENT that caused this. Understand those dynamics. Look at what forces would be applied to various parts on the loader.

As was stated, might be best (and I might think of doing this myself!*) to SLIGHTLY loosen all the mounting hardware on the loader while it's lowered and holding weight of the tractor and then re-tighten. I've heard people say they've either pulled or pushed on one arm to flex/"bend"- I'd be wary/nervous about doing this.

* My Kitoi has had an un-level loader since day one. Dealer says that they replaced it (and the saddles): I don't trust anything they say- I wasn't able to get the serial number for the loader. I later discovered that it's not as bad as I thought as the front "guard" is actually slightly off-level (I'd have to loosen it and perhaps drill out the mounting holes in order to shift).

 

[ljjhouser]

No new posts from the OP?

 

[JWR]

I've done something similar with the FEL on one of my Kubota tractors. After going through what you are right now, I came to the conclusion that I twisted the FEL frame a bit. ...

bdhsfz6 is on the right track. You do not catch a long pole/log against a tree on one side and create extra air in cylinders, valve body issues, pumps, tire pressure changes or any of the other wild ideas being posted.

Very simple. Exactly as bdhsfz6 said -- the OP "twisted the frame a bit." I have done the same thing using a MF2660 and DL250 loader (but a whole lot worse than an inch or two difference right and left) by abusing my machine trying to pry out a locust stump with one corner of the bucket. I've posted this several times. A wise shop man at my dealer said "you never heard this from me, but if you sprung it one way you can spring it the other way." I did and untwisted the loader frame. People should be aware that there are no specs of any kind on loader torque or twisting. The National Tractor Testing lab in Nebraska has no data on the topic and does not test for it. The mfrs position is "Don't do things that twist it. And if you do it is your problem." bdhsfz6's 2x8 solution is about as good as any. That really won't "untwist" it but it will take advantage of all the slop you can gain by loosening and retightening the loader frame mounting bolts. Since you have a relatively small amount of "spindling" or "twist" that'll probably take care of most of it. Then there is the Thousand dollar solution: take it to an automotive frame straightening shop (harder to find now than ever before) and they will straighten it at least as good or better than it came from the factory measurement-wise. Might be good to get an estimate if you have a bog body shop nearby.

The way you accomplished your twist, you have no realistic way to "untwist it" or cause directly opposite force in the opposite direction. If it is low on one side, you could try catching the far other side tip edge of the bucket under something solid and then put all the force you can on it in the opposite direction of the twist. I doubt you have a strong enough tractor to do that. It took momentum to create the problem and there is no reasonable way to suggest you try momentum in the other direction.

Caution: FIRST check every weld everywhere on the entire loader frame. Twice. Make sure none are broken or paint crinkled. Also use a long straight edge like a 4 foot metal ruler and check along the arms and flat surfaces and see if there is any detectable bend. That won't fix it but it will be entertaining.

 

[RancherGuy]

bdhsfz6 is on the right track. You do not catch a long pole/log against a tree on one side and create extra air in cylinders, valve body issues, pumps, tire pressure changes or any of the other wild ideas being posted.

Very simple. Exactly as bdhsfz6 said -- the OP "twisted the frame a bit."

Hmm. I'm not convinced the problem is what is commonly called a "tweaked loader". I did that to one one my loaders, and the only symptom was the bucket left side was lower than the right when placed on the ground. Mine was very visibly obvious. There was no change in cylinder behavior.

The OP's video shows that all four cylinders change length with just the pressure/weight of his footstep. To me, cylinder movement is a hydraulic system issue. If all cylinders are fully extended and retracted to purge possible air (wish he would respond with a confirmation), I would then consider that the joystick valve block has damage. That damage would be internal check valve(s) not doing their job.

 

[JWR]

Hmm. I'm not convinced the problem is what is commonly called a "tweaked loader". I did that to one one my loaders, and the only symptom was the bucket left side was lower than the right when placed on the ground. Mine was very visibly obvious. There was no change in cylinder behavior.

The OP's video shows that all four cylinders change length with just the pressure/weight of his footstep. To me, cylinder movement is a hydraulic system issue. If all cylinders are fully extended and retracted to purge possible air (wish he would respond with a confirmation), I would then consider that the joystick valve block has damage. That damage would be internal check valve(s) not doing their job.

Good point. I had glossed over the issue of the cylinders moving. I thought someone else said that was normal ??

 

[BeezFun]

Unless you have a crossover relief valve on your FEL, I would guess you damaged the internal parts of the cylinders. When the valve was in the neutral position and you hit the tree, it created a large pressure spike in the closed part of the hydraulic system that consists of the cylinders and hoses up to the point where they connect to the valve. Since the valve was in the neutral position, there is no relief on the cylinder and hoses. That's why for things like snow blades where there is likely to be a large differential force on one side of the blade that gets transmitted to that cylinder, they always install a crossover relief. I personally think there should be a crossover relief on all FELs just to address the issue you just had.

I'm not sure I can explain that excessive rod movement in your video. I could imagine the hydraulics on one side of the bucket being damaged by hitting the tree, but not the other side. Unless the long trunk you were carrying acted like a lever arm that tried to force one cylinder into retraction and the other cylinder into extension. That would damage both cylinders and could result in the excessive play you see. It's also possible the force was so large that both rods are slightly bent, maybe not enough for you to easily see it, but more than enough to allow oil to pass by. It is still puzzling that the rods move freely in the retract position. This should not be possible even if the seals are completely destroyed, so maybe there's something going on internally that I haven't' thought of.

 

[npalen]

This has to be one of the most frustrating and ill informed threads I've ever read on TBN! Anyone else feel the same?

Edit: Not directed at anyone in particular.

 

[JWR]

Didn't the OP say that everything about the loader works normally except that it sits low on one side ??

 

[Tx Jim]

This has to be one of the most frustrating and ill informed threads I've ever read on TBN! Anyone else feel the same?

Edit: Not directed at anyone in particular.

Unless JCoastie decides to reply again nobody will know the correct answer.

 

[joea99]

I was carrying a 16' log in my grapple and I clipped a standing tree on the left side. It wasn't crazy hard, i.e. the tires didn't come off the ground, but the left side of the tractor dove a bit. After it was over the loader was no longer level side to side, the left side was down about an inch and a half to two inches. I guess I was hopeful it'd be a bent SSQA torque tube which seems fairly straight forward to correct, but the SSQA faces are square. I can see nothing bent visibly.
Looking at the loader arms, one is definitely higher than the other. In use, It seems I can lift to max height evenly (as best I can tell) and I can press down so the implement sits flat on the ground, but I can also dig in more on the left side since it is uneven. I really don't know what's wrong. After I shutdown, I always relieve the hydraulic pressure by lowering the 3pt hitch, and the loader arms, I also toggle the loader joystick to release any remaining pressure once completely shut down. We often use the bucket top as a seat, and it's always been solid. This morning I noticed this (shutdown overnight and not started this morning), there is no pressure in the hydraulic system, all 4 rams move when I step on the bucket. Any ideas, and it is related to my uneven issue?

Video of what I am seeing New video by JCoastie

Well, I'm late to this party and certainly no hydraulics expert. But.

The video seems to show the bucket being rocked, just by foot pressure, with the bucket and the entire FEL frame raising and lowering in sync. Did not see anything indicating this was while running, shutdown, or what position the FEL control might be in.

While I am not the heaviest guy around, I cannot do that with my little B21 and I doubt that machine is any lighter. Pushing or extending ONE cylinder takes more effort than that, let alone FOUR. Along with the weight of the frame itself? Am I missing something? A few marbles here and there not counting?

 

[Tinhack]

I don't see any video but from the description, he probably blew the piston seal(s).