Loader bucket curl circuit gets floppy after sitting for a while

[agiardin]

I've had an L2501 that I bought 2nd hand about a year ago. Overall it's been exceptionally useful, but there's something weird with the loader bucket curl circuit. If I leave it sit, even overnight, the bucket curl circuit becomes very floppy and I have to purge air out of the system by cycling the bucket back and forth hard, multiple times. If I'm doing bucket work, this is normally a non-issue and not noticeable since the cycling just happens in the normal course of use. But if I'm back-dragging to flatten something out, using the pallet forks, trying to pry rocks out of the ground, pushing stumps over... it's a real problem. I don't notice this happening with any of the other hydraulic circuits (loader lift, loader 3rd function, backhoe, 3pt lift). It's just the loader bucket curl circuit.

Also, when air gets in the circuit, the bucket wobbles a lot. If I jump on the cutting edge of the bucket, I can move it 6+ inches. It'll move even more if I'm back dragging over rocks or something like that. With 4' pallet forks, it's even more pronounced.

Any idea what's going on here? How is the air continually getting into just the bucket curl circuit?

 

[Industrial Toys]

How many hours on the machine? I'm thinking worn seals. What else could it be?

Having said that, I have air getting into the top tilt (Brand New) cylinder I use on my JD6200. Annoying as heck! My Mennonite JD experts say it's the hydraulic system and they can fix that simply, but didn't tell me the cure. So, maybe I have air in the hydraulic system and it's just evident in the top tilt cylinder. Because I don't notice it elswhere.

 

[agiardin]

How many hours on the machine? I'm thinking worn seals. What else could it be?

Very low hours, I bought it with <60 and now have about 100. I think it was also a harvest return when the previous owner bought it from the dealer, so the loader probably has even fewer hours.

I do tend to agree though, there aren't many other ways that air could enter the circuit while the machine is off. But it just seems unlikely that the seals would go bad so fast.

 

[Industrial Toys]

Is the hydraulic fluid up? Not like the pump might be cavitating. I really should have my issue addressed as well.

 

[agiardin]

Is the hydraulic fluid up?

Yep, I keep the fluid filled up. And I would think that if air was getting sucked into the pump from the tank, all circuits would be effected, not just the loader curl circuit. And I would also think that would be something that happens when running.

 

[Industrial Toys]

That's what I would think, but in my case I only notice it on one circuit. Maybe, my case is totally different and I do have a closed centre system.

So, let's say the valve was allowing air to be sucked into the circuit when that side of the cylinder was put under suction?

 

[agiardin]

So, let's say the valve was allowing air to be sucked into the circuit when that side of the cylinder was put under suction?

That's a good point, air could be getting past either the cylinder seal or the valve seal. Any idea on how to isolate which one is causing the problem, to avoid rebuilding both? I'm thinking that I could switch the hoses on the loader valve, to swap the lift/curl function, and see if the problem stays with the curl circuit (bad seals in the cylinder) or moves to the lift circuit (bad seals in the loader valve).

 

[Industrial Toys]

I wouldn't touch anything until you get some better advice. A hydraulic guy would probably know. I have a brand new cylinder, come to think of it, I bought because I had the same issue with a smaller cylinder, also virtually unused, that I just thought was overloaded, and air was getting past the seals when put under tension.

 

[deezler]

This is pretty normal for a tractor FEL. My older Cub Cadet behaves this way too. Heck, even 5 minutes with it running will let the bucket get a bit floppy. Overnight, it goes limp.

I have the habit of grabbing the curl back lever periodically just to keep it tight.

Plenty of other threads on this site about "floppy buckets". Not real acceptable on a new machine, but good luck getting a dealer to do much of anything about it for ya.

 

[Rich B1]

Hydraulic oil expands when it is warmed up, contracts when it cools. Many hydraulic circuits will drift or get “floppy” when the oil cools.

 

[oldnslo]

Agiardan
Floppy bucket syndrome is caused when the load in the bucket causes the bucket to dump faster the oil is being pumped into the cap end of the curl cylinders. This creates a vacuum or air pocket in the cap end of theses cylinders. Simple fix is to install an orifice or flow control valve in the rod line. This restricts the oil exiting while dumping and reduces the opportunity for bucket to dump faster than oil is being pumped in.

sitting over night any air in the oil in the cylinder will separate from oil leaving an air pocket.

if you are parking the tractor with loader in the air and bucket is dumping overnight would also potentially create vacuum on cap end of the cylinders creating an air.

 

[Dave M7040]

Google "Floppy Bucket Syndrome."

A common loader bucket problem that design features like "Fast Dump," or REGEN are designed to minimize.

Loader Valve REGEN Feature Explained​

Regen is a "feature" of most modern FEL (Front End Loader) valves, it's on the Dump (joystick far right) circuit, and is also referred to as "Fast Dump". The reason it is nice to have is that without it, the weight of a filled bucket can actually "pull" the bucket down faster than the fluid can enter the other side of the cylinder, this will create a air pocket and give the bucket a "floppy" feeling until the joystick is held in the dump mode a few seconds to refill the cylinder pushing the air past the seals. So we add "regen" or "regenerative" function to the valve.

Regen solves this problem by actually filling both sides of the cylinder at the same time with hydraulic fluid. But how will that work you might ask? Well, because there is more volume on the side of the cylinder that extends it since the rod is taking up space in the other side, it "overpowers" the rod side and lets the cylinder extend-thereby dumping the bucket. So since now both sides of the cylinder are "pressurized", the air pocket can not develop, eliminating the "floppy" bucket syndrome. One other added bonus is that the bucket actually dumps faster due to the higher flow rate required to do all this, that's why it's referred to as "fast dump" sometimes.

To assess your situation, try and recall exactly what action you did with your bucket before shutting down the tractor.

Dave M7040