Cylinders Only Extend

[Sportsman762]

So I have a unique problem with a hydraulic valve that I have never seen before. Helping a friend with a Kubota M108S and a LA1403 loader that he recently bought. The tractor has open center hydraulics. When he bought the tractor the bucket was hooked up backwards. So when you moved the joystick to the right it would curl and the left it would dump. To remedy the backwards bucket I switched the lines at the quick disconnect on the loader. The bucket would dump no matter which way you moved the joystick. Move joystick to right and it would dump, move to the left and it would dump. If you set the bucket on the ground it would lift the front of the tractor when you moved to the right, but when you moved to the left it would not quite have the power to lift the front of the tractor. It has less dumping power in the position that it should be curling (left) but seems to have full power when in what should be the dump position (right). The hydraulics for the arm works just fine. I replaced the quick disconnects coupler and nipple and still have the same issue. When I loosen the lines going to the valve the one port gets more flow regardless of which way the joystick was moved.

I cannot switch the arms and the bucket as the bucket has ½” body QD and the boom has ¾” body QD. If I switch the bucket lines so that they are backwards the bucket works just fine but moving the joystick to the right it would curl and the left it would dump and this drives everyone crazy and it is apparent that there is some issue with the loader.

The valve is a Husco 5000 series sectional valve and is factory from Kubota. The valve and loader are not self leveling. The fluid is full and in good shape. When the joystick is moved the spool moves an appropriate amount in the correct directions. There are no check valves, flow restrictors or anything of that sort on the lines. I think that the bucket section on the valve has something wrong with it, however I would like to diagnose before I tear into the valve.

The tractor is 2 hours away but I should be able to test any hypothesis this weekend. Any clue on what could cause the bucket to have pressure to the butt end of the cylinder whenever the spool is actuated regardless of direction.

Sorry for the long write up. However this is a unique problem that I have been unable to find an answer to in this or any other forum. Thanks for the help.

 

[oldnslo]

What you are describing is a regenerative dump system. The valve is designed to direct pressurized oil to one end of the cylinder for curl and connects both ends together to pressure for dump. sounds like joy stick linkage is operating the valve backwards.

 

[Sportsman762]

It is not a regenerative dump system. It is only a standard 4 way 3 position valve.

 

[Seven Gables]

My first guess would be your piston seals in the dump cylinders are bypassing causing the cylinder to act as a ram

 

[K5lwq]

I would be looking closer at the couplers. If the valve works with the couplers connected one way then the valve works. Swapping the hoses on the same spool will not change that.

I am thinking one of the hose couplers does not mate well with one of the valve couplers and this is stopping flow. Then I believe there is a blown piston seal in one or both curl cylinders. This would explain what you are describing.

One thing you could try is swapping the two curl couplers on the valve then try swapping the hoses again. I think then you problem will reverse. The valve would work in the normal way of left to curl. Then when you swap them again it will only dump like it does now.

Even though this may solve the backwards joystick the piston seals should still be addressed.

 

[LD1]

I agree it sounds like a regen problem.

And it likely IS a regen valve. I know you say its a "standard 4-way 3-position" valve. Which would be incorrect regardless, if its a loader valve. More like a 7-way (if it has PB) and 5-position (if it has float) and 6-position (if it has regen bypass). But thats not really important.

ALot of kubota valves are REGEN only in dump. Meaning that there is no detent or second position when pushing right. Most people dont know this or dont care because its largely irrelevant.

THe way the loader valve is supposed to work is as follows:
When you pull the stick toward you (left)....the port connected to the rod end of the cylinder opens to the P port and the one connected to the base end of the cylinder opens to tank. By pressurizing the rod end of the cylinder......the cylinder retracts, expelling the base end fluid back to the tank.

When you push right, BOTH ports open to pressure and tank passage is closed. This causes the cylinder to extend. Also know as regen.....it extends faster but with less force. Thats not why loaders use regen.....the main reason for regen isnt to dump fast, rather its to keep the cylinder full of oil, cause when dumping a heavy load....gravity can dump the loader faster than the hydraulics can fill the cylinder with oil.....causing air and a "floppy" bucket immediately after dumping.

If you reverse the hoses on a regen system.....when pulling the lever left, you are now sending oil to the base end of the cylinder causing it to dump, rather than to the rod end causing curl. Pushing right is regen....since it pressurizes BOTH hoses.....it dont matter their orientation....it will ALWAYS dump the loader.

but what you describe...the valve ITSELF is backwards. Cause on one working correctly.....reversing the hoses sill means that BOTH left and right will dump the loader.....however it should have MORE dump power when trying to curl if the hoses are backwards.

So all of this leads me to believe when you are trying to curl...you are actually actuating the regen rather than when pushing right.

So I am suspecting linkage. Regen HAS to be when pushing right if you want it to work correctly.

Let me ask a couple simple questions:
1. Is lift normal in operation? Meaning pushing forward LOWERS the loader, and pulling backwards raises? And pushing ALL the way forward it will detent into float?
2. Is this a mechanical linkage with the joystick right on the valve? OR is it cable controlled? Cause if its cable controlled, I'd say they got the cables for the curl backwards. IF its linkage....thats a bit harder to screw up but it is possible.

Do you have any pictures of the valve and linkage?

 

[Sportsman762]

I would be looking closer at the couplers. If the valve works with the couplers connected one way then the valve works. Swapping the hoses on the same spool will not change that.

I am thinking one of the hose couplers does not mate well with one of the valve couplers and this is stopping flow. Then I believe there is a blown piston seal in one or both curl cylinders. This would explain what you are describing.

Male poppet and female coupler replaced on both lines in the spool. This was my inital though which is why I replaced them. A blown seal would cause drift in tension cylinders. The bucket stays still with no drift.

And it likely IS a regen valve. I know you say its a "standard 4-way 3-position" valve. Which would be incorrect regardless, if its a loader valve. More like a 7-way (if it has PB) and 5-position (if it has float) and 6-position (if it has regen bypass). But thats not really important.

Let me ask a couple simple questions:
1. Is lift normal in operation? Meaning pushing forward LOWERS the loader, and pulling backwards raises? And pushing ALL the way forward it will detent into float?
2. Is this a mechanical linkage with the joystick right on the valve? OR is it cable controlled? Cause if its cable controlled, I'd say they got the cables for the curl backwards. IF its linkage....thats a bit harder to screw up but it is possible.

4 way 3 position is in reference to the bucket section. The boom section is a 4 way 4 position. We both agree that this is not an important piece of information.

1.) Lift is normal operation. It has full lift and power down, the float also works.
2.) Cable controlled valve. Cables not able to be reversed. The lever is configured the same way as the parts manual shows. If the cables could be reversed I would do so as it would save me this headache.

The section that is in question is a 5002-A1, page 11 of the pdf below, a flow diagram is shown.

http://hydrodream.ru/upload/iblock/1a7/1a7acc0d2cd149bb999699da1f3f79fd.pdf

 

[ptsg]

Deleted.

 

[Sportsman762]

Its been some time, however I finally got around to working on this. I learned from the previous owner that the bucket only worked backwards after he had a guy put in a new joystick. I replaced that joystick with a Buyers B206305 joystick and two 48" Buyers B302845048 cables. I had to drill out the mounts on the tractor as the Buyers products are a Morse 43C series and the OEM is a 33C series. The loader now works great. I think it is a regenerative spool as others have mentioned. Hope this helps someone else.

 

[heathwoodhydraulics]

It seems like the issue is likely with the bucket circuit of the Husco 5000 series sectional valve. Here are a few possible causes of the problem:

1. Misaligned or damaged spool: If the spool inside the valve is not properly aligned or is damaged, it could be causing the bucket circuit to actuate in the wrong direction. This could be due to wear and tear over time, or it could be a manufacturing defect. You mentioned that the spool moves an appropriate amount in the correct directions, but it's possible that there is still a misalignment or damage that is causing the issue.

2. Blocked or restricted flow: If there is a blockage or restriction in the hydraulic lines leading to the bucket circuit, this could be causing the pressure to build up on the butt end of the cylinder, regardless of which way the spool is actuated. This could be due to debris or contamination in the hydraulic fluid, or it could be due to a kinked or damaged hydraulic line.

3. Faulty valve component: It's possible that there is a faulty component inside the valve itself, such as a faulty check valve or flow restrictor, that is causing the bucket circuit to actuate in the wrong direction. This could be due to a manufacturing defect or wear and tear over time.

To diagnose the issue, you could try disconnecting the hydraulic lines leading to the bucket circuit and checking for blockages or restrictions. You could also try swapping out the spool with a new one to see if that resolves the issue. If neither of those things work, you may need to take apart the valve and inspect the components inside for damage or wear and tear. If you're not comfortable doing this yourself, it might be best to take the tractor to a professional for repairs.