npalen
Elite Member
Probably just a little air in the cylinders and lines.
Did I bust something on the loader hydraulics?
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rScotty
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It looks good to me. I had a small tractor with a light bucket that the bucket would move like that when I stepped on the bucket lip, too - although my present 60 hp Kubota doesn't do that.
Anyway, If I was worried like it sounds you are I'd probably unmount and remount the bucket and maybe the loader too if it is QA. Just to satisfy myself that I wasn't overlooking something broken, bent, or just knocked out of alignment. . And then hook it all up and use it. It's probably OK, but if not, using it is unlikely to hurt anything.
Anyway, If I was worried like it sounds you are I'd probably unmount and remount the bucket and maybe the loader too if it is QA. Just to satisfy myself that I wasn't overlooking something broken, bent, or just knocked out of alignment. . And then hook it all up and use it. It's probably OK, but if not, using it is unlikely to hurt anything.
bdhsfz6
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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. Since everything seemed to operate correctly, I continued to use the machine with no problems. The biggest issue was I had difficulty getting a level surface when scraping or back dragging with the bucket edge. As you noticed, it would dig in on one side more than the other.
I eventually fixed the problem by doing this: I laid a 2 X 8 on the level concrete floor of my shop. I curled the bucket down and put the cutting edge on the 2 X 8. I raised the tractor front end off the ground with the FEL hydraulics. I then loosened all the FEL frame attaching bolts a couple of turns. I did this while kneeling BESIDE the tractor and NOT underneath! I raised and lowered the front end of the tractor a few times and re tightened the FEL attachment bolts with the front end off the ground.
Using this procedure, I was able to get the bucket to within a quarter inch of level. Before, it was out more than an inch.
Again, this was on a Kubota. I don't know if it will work on your LS but it may be worth a try.
I eventually fixed the problem by doing this: I laid a 2 X 8 on the level concrete floor of my shop. I curled the bucket down and put the cutting edge on the 2 X 8. I raised the tractor front end off the ground with the FEL hydraulics. I then loosened all the FEL frame attaching bolts a couple of turns. I did this while kneeling BESIDE the tractor and NOT underneath! I raised and lowered the front end of the tractor a few times and re tightened the FEL attachment bolts with the front end off the ground.
Using this procedure, I was able to get the bucket to within a quarter inch of level. Before, it was out more than an inch.
Again, this was on a Kubota. I don't know if it will work on your LS but it may be worth a try.
Tx Jim
New Member
May I ask how you think air can enter a sealed hyd system?
Billrog
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You must be right Jim, it's just some thing I assumed since it's not be uncommon to may tractors.
npalen
Elite Member
Usually via the pump.
Edit: Also, on a loader with a lot of weight and letting it down quickly and then closing the valve. The pump can't keep up.
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Billrog
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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.
npalen
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Billrog
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Because all four rods move wouldn't that indicate something in the valve body ? How this happens when every thing functions as it should is puzzling and to boot the bucket is no longer level. Will be interesting to see the answer.
Vigo327
Platinum Member
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!
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!
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