LA302 Lost Bucket Roll Back Function

[Rusty46]

I lost the roll back function on my Kubota LA302 front loader and need some help finding the cause and fixing it.

I was using the loader to move my compost pile from point A to point B for the winter. The pile was about 1/2 moved when the roll back function stopped working after a bucket dump. No apparent strain, no abnormal sound, no leaks.

I bought the B7500 HSD-R tractor and LA 302 front loader new in 2003 and have been using both for twenty years. Most, if not all the hoses direct to/from the boom and bucket cylinders have been replaced at one time or another. A Tach-N-Go quick attach from MYTRACTORTOOLS.com was added in 2020. All four bucket and boom cylinders were rebuilt professionally in 2022. The loader valve is a I JSCO International Inc. 3 Position Bucket Control (for Roll Back & Dump), H02A3954 05, Kubota P/N 7J043-61011, S/N (?) 9210-B2B C. The loader S/N is <=99999.

I have very little practical hydraulic experience. I have read several similar threads here on OTT. I have a PDF copy of the WORKSHOP Manual (WSM).

So far, I have checked for leaks (none found); checked UDT2 level (was at low limit, added one qt); cycled joystick to purge air; looked for unseated quick connection(s) (none found); cleaned, blown out with compressed air and reseated all four quick couplers (multiple times); Tried the 3-point lever in neutral, down and up positions; checked the joystick linkage (no apparent problem); and swapped the roll back/dump hoses, and the roll back/dump and box up/down hoses (did not regain roll back).

I was able to disconnect and secure the bucket by disconnecting both hoses on the two bucket cylinders and making an oily mess.

I will greatly appreciate suggestions on how to proceed!

 

[Dave_eng]

I suggest you should suspect a quick connect coupling to have become partially unseated.
Disconnect and reconnect the couplers for the bucket.
Advise us if this works or does not please.
Dave

 

[TheOldHokie]

I lost the roll back function on my Kubota LA302 front loader and need some help finding the cause and fixing it.

I was using the loader to move my compost pile from point A to point B for the winter. The pile was about 1/2 moved when the roll back function stopped working after a bucket dump. No apparent strain, no abnormal sound, no leaks.

I bought the B7500 HSD-R tractor and LA 302 front loader new in 2003 and have been using both for twenty years. Most, if not all the hoses direct to/from the boom and bucket cylinders have been replaced at one time or another. A Tach-N-Go quick attach from MYTRACTORTOOLS.com was added in 2020. All four bucket and boom cylinders were rebuilt professionally in 2022. The loader valve is a I JSCO International Inc. 3 Position Bucket Control (for Roll Back & Dump), H02A3954 05, Kubota P/N 7J043-61011, S/N (?) 9210-B2B C. The loader S/N is <=99999.

I have very little practical hydraulic experience. I have read several similar threads here on OTT. I have a PDF copy of the WORKSHOP Manual (WSM).

So far, I have checked for leaks (none found); checked UDT2 level (was at low limit, added one qt); cycled joystick to purge air; looked for unseated quick connection(s) (none found); cleaned, blown out with compressed air and reseated all four quick couplers (multiple times); Tried the 3-point lever in neutral, down and up positions; checked the joystick linkage (no apparent problem); and swapped the roll back/dump hoses, and the roll back/dump and box up/down hoses (did not regain roll back).

I was able to disconnect and secure the bucket by disconnecting both hoses on the two bucket cylinders and making an oily mess.

I will greatly appreciate suggestions on how to proceed!

If dump still works but curl does not I would suspect the tank return connection.

Dan

 

[Rusty46]

I suggest you should suspect a quick connect coupling to have become partially unseated.
Disconnect and reconnect the couplers for the bucket.
Advise us if this works or does not please.
Dave

Dave - I have disconnected and reconnected all four couplings multiple times and they have always felt and looked seated. Is there another way to verify that a coupling is seated/open to flow?

 

[Rusty46]

If dump still works but curl does not I would suspect the tank return connection.

Dan

Dan - Thanks, I don't know that dump still works, as the bucket cylinder is now fully extended. I don't know if it extended by pressure or its own weight.

 

[Missouribound]

I vote for the coupler connection as well.
It has happened to me on a couple of occasions.

 

[TheOldHokie]

Dan - Thanks, I don't know that dump still works, as the bucket cylinder is now fully extended. I don't know if it extended by pressure or its own weight.

I looked at the parts diagram and the return line is all hard connections so it's not likely to be the return line. Remove and reconnect the bucket couplers.

Dan

 

[Jasonized]

Have you tried swapping functions to see if it follows? I.e., swap curl lines with lift lines. If the valve is faulty, you can curl but not lift then…. If you still cant curl, then you’ve narrowed down functions.

 

[Rusty46]

Missouribound posted "I vote for the coupler connection as well.
It has happened to me on a couple of occasions."

I looked at the parts diagram and the return line is all hard connections so it's not likely to be the return line. Remove and reconnect the bucket couplers.

Dan

Missouribound & Dan - With the tractor not running, I cycled the joy stick thru the four main functions. I disconnected all four couplings at one time, and reconnected all four, and started tractor. No roll back. Then with the tractor not running, I cycled the joy stick thru the seven function positions, discontinued and reconnected the four couplings one at a time, started the tractor. No roll back.

Jasonized posted "Have you tried swapping functions to see if it follows? I.e., swap curl lines with lift lines. If the valve is faulty, you can curl but not lift then…. If you still cant curl, then you’ve narrowed down functions."

Jasonized - Thanks, yes I did try swapping functions. Still no roll back, but I didn't make any notes of. what else did or did not work. I will try swapping again tomorrow and make some notes.

 

[Jasonized]

Jasonized - Thanks, yes I did try swapping functions. Still no roll back, but I didn't make any notes of. what else did or did not work. I will try swapping again tomorrow and make some notes.

Okay, so swapping didn’t “move” the problem. Eliminates all things involved in the swap! Means valves, connections at the valve, because the same connections worked when swapped. So, this seems to me like you are down to the lines going to the curl function, or the cylinder itself.
good luck!

 

[07wingnut]

There is the off chance that the ram for the curl function has become disconnected internally from the piston. If this is the case, trying to roll back merely allows the hydraulic fluid to pass thru the piston hole that is now open becauseof the disconnect.

 

[TheOldHokie]

Missouribound posted "I vote for the coupler connection as well.
It has happened to me on a couple of occasions."



Missouribound & Dan - With the tractor not running, I cycled the joy stick thru the four main functions. I disconnected all four couplings at one time, and reconnected all four, and started tractor. No roll back. Then with the tractor not running, I cycled the joy stick thru the seven function positions, discontinued and reconnected the four couplings one at a time, started the tractor. No roll back.

Jasonized posted "Have you tried swapping functions to see if it follows? I.e., swap curl lines with lift lines. If the valve is faulty, you can curl but not lift then…. If you still cant curl, then you’ve narrowed down functions."

Jasonized - Thanks, yes I did try swapping functions. Still no roll back, but I didn't make any notes of. what else did or did not work. I will try swapping again tomorrow and make some notes.

Stop swapping things around. You are just adding to the confusion and risk getting things misconnected. You have lost one function - curl. Stick to just that circuit. You told is this was a spontaneous failure while operating so I am ruling out misconnections. Let's test borh halves of the curl circuit.

With tractor off and all couplers connected as normal:

1. Disconnect the hose from the male coupler going to the rod end of the bucket cylinders, start tractor and try to curl. You should get oil out of the disconnected coupler. If no.oil flow that coupler is defective or the spool is not shifting. Stop here.

2. If you get oil in test #1 reconnect hose and disconnect the hose on the male coupler going to base end of bucket cylinder, start tractor and try curl. You should get oil from that hose and bucket should curl.

Reconnect all hoses and report findings.

Dan

 

[Dave_eng]

I lost the roll back function on my Kubota LA302 front loader and need some help finding the cause and fixing it.

I was using the loader to move my compost pile from point A to point B for the winter. The pile was about 1/2 moved when the roll back function stopped working after a bucket dump. No apparent strain, no abnormal sound, no leaks.

I bought the B7500 HSD-R tractor and LA 302 front loader new in 2003 and have been using both for twenty years. Most, if not all the hoses direct to/from the boom and bucket cylinders have been replaced at one time or another. A Tach-N-Go quick attach from MYTRACTORTOOLS.com was added in 2020. All four bucket and boom cylinders were rebuilt professionally in 2022. The loader valve is a I JSCO International Inc. 3 Position Bucket Control (for Roll Back & Dump), H02A3954 05, Kubota P/N 7J043-61011, S/N (?) 9210-B2B C. The loader S/N is <=99999.

I have very little practical hydraulic experience. I have read several similar threads here on OTT. I have a PDF copy of the WORKSHOP Manual (WSM).

So far, I have checked for leaks (none found); checked UDT2 level (was at low limit, added one qt); cycled joystick to purge air; looked for unseated quick connection(s) (none found); cleaned, blown out with compressed air and reseated all four quick couplers (multiple times); Tried the 3-point lever in neutral, down and up positions; checked the joystick linkage (no apparent problem); and swapped the roll back/dump hoses, and the roll back/dump and box up/down hoses (did not regain roll back).

I was able to disconnect and secure the bucket by disconnecting both hoses on the two bucket cylinders and making an oily mess.

I will greatly appreciate suggestions on how to proceed!

From memory, forum leader Whitetiger, who is also a Kubota tech, has advised that couplers can fail internally. I would invest in two new couplers as the lowest cost approach.

I will also attach a testing procedure for double acting cylinders. This will confirm if cylinder piston is no longer connected to push rod.

Dave

 

[TheOldHokie]

From memory, forum leader Whitetiger, who is also a Kubota tech, has advised that couplers can fail internally. I would invest in two new couplers as the lowest cost approach.

I will also attach a testing procedure for double acting cylinders. This will confirm if cylinder piston is no longer connected to push rod.

Dave

Checking the flow at both hoses will tell you all of that and more.

Dan

 

[Jasonized]

1. Disconnect the hose from the male coupler going to the rod end of the bucket cylinders, start tractor and try to curl. You should get oil out of the disconnected coupler. If no.oil flow that coupler is defective or the spool is not shifting. Stop here.

2. If you get oil in test #1 reconnect hose and disconnect the hose on the male coupler going to base end of bucket cylinder, start tractor and try curl. You should get oil from that hose and bucket should curl.

Reconnect all hoses and report findings.

Dan

yep! he already swapped and got info. So no need to swap more. lines are next, and you stepped through both quite nicely. Careful, could be messy. Although, I would rule out the spool not shifting at this point, because he swapped functions and the problem did not move. So the spool is most likely fine.

 

[GreensvilleJay]

hmm...ANY chance the joystick isn't moving the valve properly ??
Have you confirmed it actually move the spool valve shaft BOTH ways ?

My right BH joystick BROKE off ( kinda obvious ) , $30 to fix.....

 

[TheOldHokie]

hmm...ANY chance the joystick isn't moving the valve properly ??
Have you confirmed it actually move the spool valve shaft BOTH ways ?

My right BH joystick BROKE off ( kinda obvious ) , $30 to fix.....

Yes there is a very real chance. Thats one of the possibilities the first hose test would rule out.

Dan

 

[Henro]

At this point I would just buy two new coupling pairs for the function in question and change them both.

IF I needed to know if it is the couplers before purchasing new ones, I would swap the couplers between the lift and roll functions and see if it made a difference. Probably would do it one pair at a time, thereby isolating it to the one bad coupler, if indeed one coupler is bad.

edit: thinking about it, I would probably first take BOTH hoses of one of the tilt cylinders, and try the valve in both positions and watch and see which hose did not spew oil out and if one did not, that is the coupler I would change.

AND if I really wanted to know, I would remove the coupler from the valve, and shift the valve and see if fluid then came out of the valve to ensure the issue was with the coupler and not the valve itself.

I think Dan already covered this approach...but in two steps.

 

[TheOldHokie]

At this point I would just buy two new coupling pairs for the function in question and change them both.

IF I needed to know if it is the couplers before purchasing new ones, I would swap the couplers between the lift and roll functions and see if it made a difference. Probably would do it one pair at a time, thereby isolating it to the one bad coupler, if indeed one coupler is bad.

Edit - sorry wrong post quoted but zi am not going to fix it

If you dont go hog wild by holding the valve open a shop rag will control the mess.

Dan

 

[Jasonized]

Yes there is a very real chance. Thats one of the possibilities the first hose test would rule out.

Dan

it’s already been ruled out…. Swapping the lines and the problem didn’t move with it means both spools have been tested in both directions and have been found working.
if one of the spools didn’t work, the problem would have moved to the other action. It didn’t. So the problem is beyond it, I.e, the hoses or connections on the hose half, or the cylinder.
Your hose to bucket test would rule out the connectors. If those work, what’s left is the cylinder.