Issues with loader dump after overpressure/blown line L5460

[CdnSldr.ret]

Hey folks, looking to see if anyone has any insight on this issue before contacting Kubota insurance and the dealer on Monday. Here is the story.

I’ve got a 2018 L5460 with the LA1055 loader. Only 600 hours. I was moving large rocks with pallet forks and was “rolling” rocks that were too big to pick up. One particularly large rock rolled back onto the forks and caused overpressure blowing out the hard line for the bucket curl that runs from the loader valve to the quick connects. I was pretty surprised that the hard line was the weak link and not one of the flexible lines.





I changed the blown line and did a full HST/hydraulic fluid change with new filters as it was slightly overdue.

I’m now having issues with the loader dump. The dump only really works when the joystick is moved just slightly to the right. If I move the joystick all the way to the detent, or beyond into regen dump, the dump is either incredibly slow or stalls and loads the engine.

I suspect that the overpressure situation caused some issues in the spool.

I tried all of the easy fixes:
-hydraulic oil is at proper level
-checking linkage to the loader valve
-reconnecting the quick connects
-swapping circuits/reversing the connections to test.

When reversing the dump/curl quick connects the bucket would only dump not curl. When swapping the loader arm circuit and the bucket circuit, the loader would only raise and not lower. These results are suggesting to me that the dump curious downstream of the quick connects is working properly. It would also suggest that the loader valve is not providing adequate flow/pressure to the dump circuit.

I wasn’t able to find much by scouring the internet but did find examples of a poppet stem breaking off in the valve spool causing similar issues.

 

[TheOldHokie]

Hey folks, looking to see if anyone has any insight on this issue before contacting Kubota insurance and the dealer on Monday. Here is the story.

I’ve got a 2018 L5460 with the LA1055 loader. Only 600 hours. I was moving large rocks with pallet forks and was “rolling” rocks that were too big to pick up. One particularly large rock rolled back onto the forks and caused overpressure blowing out the hard line for the bucket curl that runs from the loader valve to the quick connects. I was pretty surprised that the hard line was the weak link and not one of the flexible lines.

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I changed the blown line and did a full HST/hydraulic fluid change with new filters as it was slightly overdue.

I’m now having issues with the loader dump. The dump only really works when the joystick is moved just slightly to the right. If I move the joystick all the way to the detent, or beyond into regen dump, the dump is either incredibly slow or stalls and loads the engine.

I suspect that the overpressure situation caused some issues in the spool.

I tried all of the easy fixes:
-hydraulic oil is at proper level
-checking linkage to the loader valve
-reconnecting the quick connects
-swapping circuits/reversing the connections to test.

When reversing the dump/curl quick connects the bucket would only dump not curl. When swapping the loader arm circuit and the bucket circuit, the loader would only raise and not lower. These results are suggesting to me that the dump curious downstream of the quick connects is working properly. It would also suggest that the loader valve is not providing adequate flow/pressure to the dump circuit.

I wasn’t able to find much by scouring the internet but did find examples of a poppet stem breaking off in the valve spool causing similar issues.

Number 1 - you cannot reverse the dump and curl connections.

Number 2 - flow rate not pressure controls cylinder speed.

Now put boom and bucket back as it was and lets start with some real diagnosis.

Dan

 

[CdnSldr.ret]

Number 1 - you cannot reverse the dump and curl connections.

Number 2 - flow rate not pressure controls cylinder speed.

Now put boom and bucket back as it was and lets start with some real diagnosis.

Dan

Everything is back to as it should be. Those steps were simply part of verifying that A) the quick connect fitting isn’t the issue and B) the circuit downstream of the quick connect is operating as it should.

What would be your recommendation for the next steps of “real diagnosis”?

 

[TheOldHokie]

Everything is back to as it should be. Those steps were simply part of verifying that A) the quick connect fitting isn’t the issue and B) the circuit downstream of the quick connect is operating as it should.

What would be your recommendation for the next steps of “real diagnosis”?

Lets start with a clean description of the bucket behavior.

1. Does the bucket curl correctly?
2. What does the bucket do when the joystick is moved to the first dump position?
3. What does the bucket do when the joystick is moved to the second dump position?

Dan

 

[CdnSldr.ret]

Lets start with a clean description of the bucket behavior.

1. Does the bucket curl correctly?
2. What does the bucket do when the joystick is moved to the first dump position?
3. What does the bucket do when the joystick is moved to the second dump position?

Dan

I thought I did that in the original post but here’s more detail.

1. bucket curl and all other functions (except dump) appear to operate normally.
2. bucket dump will operate at reduced speed if I move the joystick ever so slightly to the right ( say 5% of total joystick travel) as soon as I push beyond 5% (still far away from the soft stop/regen) the bucket dump slows to a creep or stops completely and loads up the engine). From the point at which dump drastically slows or stalls, there is no change when I push the joystick far right into regen mode.
3. Answer above. No change

 

[TheOldHokie]

I thought I did that in the original post but here’s more detail.

1. bucket curl and all other functions (except dump) appear to operate normally.
2. bucket dump will operate at reduced speed if I move the joystick ever so slightly to the right ( say 5% of total joystick travel) as soon as I push beyond 5% (still far away from the soft stop/regen) the bucket dump slows to a creep or stops completely and loads up the engine). From the point at which dump drastically slows or stalls, there is no change when I push the joystick far right into regen mode.
3. Answer above. No change

OK - lets get our terminology clear.

The bucket has two dump positions separated by a detent.

Position 1 is fast dump or regen. In this position return oil from the cylinder is combined with pressureized oil from the pump to increase cylinder speed but at reduced dump force


Position 2 is standard dump and return oil is sent to tank. Cylinder speed is reduced but full dump force is obtained.

For the first diagnostic test disconnect the quick coupler on the rod end hose and remove the coupler from the hose. Put the open end if the hose in a clean container and test operation of both dump positions.

Dan

 

[CdnSldr.ret]

OK - lets get our terminology clear.

The bucket has two dump positions separated by a detent.

Position 1 is fast dump or regen. In this position return oil from the cylinder is combined with pressureized oil from the pump to increase cylinder speed but at reduced dump force


Position 2 is standard dump and return oil is sent to tank. Cylinder speed is reduced but full dump force is obtained.

For the first first diagnostic test disconnect the quick coupler on the rod end hose and remove the coupler. Put yhe open end if the hose in a clean container and test both dump positions.

Dan

My bad on that, I thought first position was standard power dump and 2nd was regenerative dump.

Will try that when I get home.

 

[CdnSldr.ret]

OK - lets get our terminology clear.

The bucket has two dump positions separated by a detent.

Position 1 is fast dump or regen. In this position return oil from the cylinder is combined with pressureized oil from the pump to increase cylinder speed but at reduced dump force


Position 2 is standard dump and return oil is sent to tank. Cylinder speed is reduced but full dump force is obtained.

For the first diagnostic test disconnect the quick coupler on the rod end hose and remove the coupler from the hose. Put the open end if the hose in a clean container and test operation of both dump positions.

Dan

After disconnecting the female end of the QC on the rod side, the bucket fully droops when the loader is raised and dumps all of the fluid on the rod side into the bucket without any joystick input.

Dumping the bucket after that in either position does not yield any fluid coming out of the rod end hose.

I linked a video. Let me know if it doesn’t work.

http://imgur.com/a/ZrMmgO8

 

[TheOldHokie]

After disconnecting the female end of the QC on the rod side, the bucket fully droops when the loader is raised and dumps all of the fluid on the rod side into the bucket without any joystick input.

Dumping the bucket after that in either position does not yield any fluid coming out of the rod end hose.

I linked a video. Let me know if it doesn’t work.

http://imgur.com/a/ZrMmgO8

I should have guven you better instructions. Reconnect everything and fully curl the bucket. Now put the bucket on the ground so it doesn't dump of its own weight when you disconnect the rid end hose.

Now repeat the test without raising the boom. You cannot curl the bucket with that hose disconnected. If you need to retract the cylinders you will have to reconnect the couplers.

Dan

 

[CdnSldr.ret]

I should have guven you better instructions. Reconnect everything and fully curl the bucket. Now put the bucket on the ground so it doesn't dump of its own weight when you disconnect the rid end hose.

Now repeat the test without raising the boom. You cannot curl the bucket with that hose disconnected. If you need to retract the cylinders you will have to reconnect the couplers.

Dan

Re doing that test with the bucket on the ground, the bucket dumps in both positions and fluid drains from the rod end hose when dumping. In both positions there is enough dumping force to lift the front of the tractor.

An interesting thing I noticed is that after disconnecting lines, either QC’s or unthreading fittings, the dump circuit appears to work normally for a couple cycles. After curling and dumping a few times the same symptoms show up and gradually worsens.

 

[Russell King]

Move the FEL lever to the opposite function (curl?) and see if fluid comes out of that hose.

 

[TheOldHokie]

Re doing that test with the bucket on the ground, the bucket dumps in both positions and fluid drains from the rod end hose when dumping. In both positions there is enough dumping force to lift the front of the tractor

So what does that tell you? It tells me there is a problem with the return side circuit. What could it pissibly be? My first thought is the coupler.

Reconnect everything and curl the bucket. Put the bucket on the ground and this time disconnect the male quick coupler on the valve and leave the male a and female connected. Repeat the test.

DO NOT ATTEMPT TO CURL THE BUCKET WITH NOTHING CONNECTED TO THAT PORT ON THE VALVE

Dab

 

[CdnSldr.ret]

Move the FEL lever to the opposite function (curl?) and see if fluid comes out of that hose.

Curl supply (rod end) is blocked at the male QC that is disconnected, but no it doesn’t,

 

[TheOldHokie]

Curl supply (rod end) is blocked at the male QC that is disconnected, but no it doesn’t,

Forget that - curl works

Repeat the dump test as I described and make sure you dont move to curl.

Dan

 

[CdnSldr.ret]

I re did the test forcing the rod end fluid through the QC. Same as last test. The QC appears to be fine. A messy test, as the first position of dump (regen) also supplies fluid to the rod end (fluid came out the port with the removed male QC when in regen position but not standard dump).

An edit you might not have seen on last post. Bucket dump seems to work well for few cycles of dump/curl then gradually slows to a crawl.

 

[TheOldHokie]

I re did the test forcing the rod end fluid through the QC. Same as last test. The QC appears to be fine. A messy test, as the first position of dump (regen) also supplies fluid to the rod end (fluid came out the port with the removed male QC when in regen position but not standard dump).

An edit you might not have seen on last post. Bucket dump seems to work well for few cycles of dump/curl then gradually slows to a crawl.

My bad again!! Yes both ports get pressure in regen. I should have realized that.

This isnt making much sense.

In regen there is no return oil.
In standard dump return oil goes to tank.

if the rod end coupker is working both directions I cant see how regen (posution 1) can't work. That's basic physics. Please verify the coupker works in both directions.

 

[CdnSldr.ret]

My bad again!! Yes both ports get pressure in regen. I should have realized that.

This isnt making much sense.

In regen there is no return oil.
In standard dump return oil goes to tank.

if the rod end coupker is working both directions I cant see how regen (posution 1) can't work. That's basic physics. Please verify the coupker works in both directions.

In regen there is return oil from the rod end to the spool then it gets diverted to the piston end. Yes flow is supplied to both sides but the larger piston end overpowers the rod end and forces return flow. From my understanding, everything to do with regen happens in the spool/valve.

I suspect there are issues with the return side in the spool. I’d imagine the spool is multi piece with a variety of springs. Something likely got buggered with the pressure spike.

I had already tested the coupler in the other direction and it appeared fine. Also, a functioning curl would suggest it’s fine.

 

[TheOldHokie]

In regen there is return oil from the rod end to the spool then it gets diverted to the piston end. Yes flow is supplied to both sides but the larger piston end overpowers the rod end and forces return flow. From my understanding, everything to do with regen happens in the spool/valve.

I suspect there are issues with the return side in the spool. I’d imagine the spool is multi piece with a variety of springs. Something likely got buggered with the pressure spike.

I had already tested the coupler in the other direction and it appeared fine. Also, a functioning curl would suggest it’s fine.

In regen both ports get connected to full pump pressure and each other. The force diifferential across the piston displaces the rod causing oil to loop back to the base end so yes there is reverse flow between the ports but its all internal to the valve.

In standard dump rod end return flow goes to tank

The spool is one piece with annular rings that route the oil to the internal passages. No springs, no seals.

I am having a very hard time coming up with a failure that affects both operations.

Dan

 

[CdnSldr.ret]

In regen both ports get connected to full pump pressure and each other. The force diifferential across the piston displaces the rod causing oil to loop back to the base end so yes there is reverse flow between the ports but its all internal to the valve.

In standard dump rod end return flow goes to tank

The spool is one piece with annular rings that route the oil to the internal passages. No springs, no seals.

I am having a very hard time coming up with a failure that affects both operations.

Dan

In my searching I found this video that talks about a broken check valve wedge that affects curl/dump. Any thoughts on that?

 

[TheOldHokie]

In my searching I found this video that talks about a broken check valve wedge that affects curl/dump. Any thoughts on that?

Yes - that thought did cross my mind but I cant formulate a failure.

Thats the load check valve that holds the load side pressure untill pump side pressure rises to match. Its easy to examine.