Did I bust something on the loader hydraulics?

Smokeydog · Mar 1, 2022

Moving some large oak logs and heard a loud TIC.
Loader was down a little on the right. No broken welds, by measuring not twisted. Tried straightening by lifting and bumping the left side. When running the tractor it would level. When parked it would drop always to the right but while running be level. Never could figure out what got tweaked.

rScotty · Mar 1, 2022

Chainsaw. said:
What Tx Jim said, that ain’t right, for a couple of reasons. As he stated the valve shouldn’t let fluid pass while its in the neutral position. Also, the cylinders should have enough drag on them just from the seals that they should take a bit of force to move in and out. But if that were happening they should also be slobbering fluid from being to loose. I’ve worked on alot of cylinders and that is very weird.

I disagreed, so this afternoon I went out and tried it on our Kubota. It has excellent hydraulics and no problems. So I drove it around to warm it up, put the bucket down in the same position as the OP did with his in the video on message 1 page 1, turned off the engine, and then worked the loader control stick to take all the pressure off the hydraulics.
Then I went around to the front & put my foot on the bucket lip. Guess what? I found that it works up and down just exactly like the one in the video.
You tell me why.
rScotty

npalen · Mar 1, 2022

rScotty said:
I disagreed, so this afternoon I went out and tried it on our Kubota. It has excellent hydraulics and no problems. So I drove it around to warm it up, put the bucket down in the same position as the OP did with his in the video on message 1 page 1, turned off the engine, and then worked the loader control stick to take all the pressure off the hydraulics.
Then I went around to the front & put my foot on the bucket lip. Guess what? I found that it works up and down just exactly like the one in the video.
You tell me why.
rScotty

It has to be air in the cylinders. See posts #22, #28 and #47.

Edit: and your post #26

rScotty · Mar 1, 2022

npalen said:
It has to be air in the cylinders. See posts #22, #28 and #47.

Edit: and your post #26

It might be air. We know that all fluids have some entrained air. It could also be something as simple as the elasticity of the hoses. Or something we haven't considered yet.

If it is air, then the next question is how much air is normal? I've always wondered about that. I don't like bouncy loaders, so in an effort to change things I've tried many different ways to empty the hydaulics of air. Near as I can tell, no combination of nose up, down, level, raising, and lowering has made any difference at all. Maybe trapped air is what makes a loader bucket bounce, but if so, it doesn't seem to affect FEL ability to lift and hold loads.

Speaking of doing experiments, I've always felt that experiments were worth more than opinions. We are now over 100 posts in this thread. I encourage others to try the experiment on their own tractor. It's easy. Put the bucket onthe ground, shut off the engine, work the stick to let the hydraulics relax. Now go step on the bucket lip to get it rocking and see what - if anything - happens with the bucket and lift cylinders.
rScotty

npalen · Mar 1, 2022

rScotty said:
It might be air. We know that all fluids have some entrained air. It could also be something as simple as the elasticity of the hoses. Or something we haven't considered yet.

If it is air, then the next question is how much air is normal? I've always wondered about that. I don't like bouncy loaders, so in an effort to change things I've tried many different ways to empty the hydaulics of air. Near as I can tell, no combination of nose up, down, level, raising, and lowering has made any difference at all. Maybe trapped air is what makes a loader bucket bounce, but if so, it doesn't seem to affect FEL ability to lift and hold loads.

Speaking of doing experiments, I've always felt that experiments were worth more than opinions. We are now over 100 posts in this thread. I encourage others to try the experiment on their own tractor. It's easy. Put the bucket onthe ground, shut off the engine, work the stick to let the hydraulics relax. Now go step on the bucket lip to get it rocking and see what - if anything - happens with the bucket and lift cylinders.
rScotty

A video or photo of the experiment is a plus also. So did you leave the bucket tilted up so the cutting edge was a couple inches above the surface and then step on the cutting edge to make it tilt down to the surface?
Did any of the cylinders move when you took the pressure off the hydraulics? Did the boom cylinders move also when you stepped on the bucket? What besides air in the cylinders would let the bucket tilt down by simply stepping on it?

I think that loader cylinders are especially vulnerable to air that is sucked in when tilting the bucket or lowering the boom especially when loaded. This is exacerbated when the load is dropped quickly and with lower engine RPM as the hydraulic pump cant replenish fluid fast enough behind the rapidly moving piston.
Dropping the loader slowly overcomes this issue by allowing the pump to "keep up".

Edit: corrected spelling

bdhsfz6 · Mar 2, 2022

rScotty said:
It might be air. We know that all fluids have some entrained air. It could also be something as simple as the elasticity of the hoses. Or something we haven't considered yet.

If it is air, then the next question is how much air is normal? I've always wondered about that. I don't like bouncy loaders, so in an effort to change things I've tried many different ways to empty the hydaulics of air. Near as I can tell, no combination of nose up, down, level, raising, and lowering has made any difference at all. Maybe trapped air is what makes a loader bucket bounce, but if so, it doesn't seem to affect FEL ability to lift and hold loads.

Speaking of doing experiments, I've always felt that experiments were worth more than opinions. We are now over 100 posts in this thread. I encourage others to try the experiment on their own tractor. It's easy. Put the bucket onthe ground, shut off the engine, work the stick to let the hydraulics relax. Now go step on the bucket lip to get it rocking and see what - if anything - happens with the bucket and lift cylinders.
rScotty

I've owned 7 Kubota tractors over the years and ALL of them did this to some extent. It does no harm and FEL performance isn't affected at all so I've always assumed it is normal.

It certainly doesn't warrant a service call or even a complaint since the issue goes away as soon as the engine is started.

npalen · Mar 2, 2022

I've noticed, also over the years, is that it takes a second or two to start lifting the front of the tractor off the ground, after the valve is pushed forward, especially at low idle. This is another result of air in the cylinders that has to compress enough, with piston travel in the cylinders, to start lifting the front of the tractor.

As a side note, lifting the front of the tractor off the ground is not something one would do routinely but rather, for example, as a way to change a front tire or perhaps to make shifting in and out of FWA easier.

Yes, I would encourage folks to experiment, safely, to become familiar with hydraulics in general.

npalen · Mar 2, 2022

bdhsfz6 said:
I've owned 7 Kubota tractors over the years and ALL of them did this to some extent. It does no harm and FEL performance isn't affected at all so I've always assumed it is normal.

It certainly doesn't warrant a service call or even a complaint since the issue goes away as soon as the engine is started.

Does the issue go away when the engine is started or when the valve is operated and does it really "go away" or just not noticed?