HELP! My Backhoe won't swing left!

[avc8130]

Bringing this back up again. My L45 is exhibiting the "won't swing left" again. It swings right. If I move the joystick full left nothing seems to happen but gravity can swing the boom left. If I move the stick SLIGHTLY left I can hear flow at the valve. I've tried the usual high rpm, right stabilizer up, gravity return a bunch of times with no luck. All portions of the control linkage are tight and in nice condition.

Not sure where to go from here.

ac

 

[Smokeydog]

I remember reading about this topic before I bought a used bt1200 backhoe for the M59. After mounting and operating the first few times momentarily lost boom down pressure and left swing at different times. No change in sound or other functions. Kept trying and eventually power came back. Not sure how long the backhoe attachment had set not attached. Hope it’s just a intermittent occurrence. Stuck relief valve maybe be the problem.

 

[rScotty]

I just wish we knew WHY.

ac

So do I. This comes up every few years for Kubota TLBs and has for a decade now and no answers. I stand by what I wrote in posts #10 & 12, I think...

To save you time in the wayback machine, I lean toward the "crud in the relief valve" theory myself... but only barely. I have absolutely no evidence of it actually being that relief valve, and am at a loss to explain why other relief valves don't have the same problem.

Good news is that so far nobody has associated this glitch with any type of long term mechanical failure - at least not that I've heard of. And every single time this has happened it eventually resolved on it's own. Although not without a lot of working the controls, repeated tilting, and moving those two backhoe hydraulic power feed levers a few times. The levers located right above the PTO shaft.

Hoping that someday one of us will figure it out.
rScotty

 

[avc8130]

I flat out ran out of time today to fiddle with it before it ever started working again. I must've cycled it 5-6 DOZEN times in 4 different occasions. Never did get the task I needed to do done.

It amazes me how common this is, but no one seems to know why. This is my second Kubota with this "feature".

Next time I get to the machine I'll try fiddling with the valve selectors. Anyone remember which side is the swing/steering pump?

It also seems this issue only occurs on the swing circuit? I wonder if that has something to do with it?

ac

 

[rScotty]

I flat out ran out of time today to fiddle with it before it ever started working again. I must've cycled it 5-6 DOZEN times in 4 different occasions. Never did get the task I needed to do done.

It amazes me how common this is, but no one seems to know why. This is my second Kubota with this "feature".

Next time I get to the machine I'll try fiddling with the valve selectors. Anyone remember which side is the swing/steering pump?

It also seems this issue only occurs on the swing circuit? I wonder if that has something to do with it?

ac

Good observation ac, I don't believe the problem has ever been reported in any of the other circuits. Only in the swing circuit.

On mine it was 5 years before the first (and only) episode, and has been 7 years since without a repeat. The flow direction control valve levers are pushed in for BH and pulled out for 3pt operation. The swing lever is the LH one, LH being the same side that you get on and off of a tractor, or horse, or motorcycle.

The British very reasonably call that LH side from which one mounts the steed as the "onside".
And with their typical logic, they call the other side - the other remaining unused side - as the "offside". Not that anyone ever deliberately exits on the offside, but simply because it is the the opposite of "onside". OK? I do hope that helps.....

Standing behind the tractor, If you peer forward along that LH or onside hyd. fluid direction control valve rod as it passes through a body panel and disappears into the bowels of the machine, the piece sticking out the casting that just misses being hit by the rod is the swing circuit relief valve. So if you are standing back there and sighting along the rod, the relief valve is just slightly to starboard and halfway along the length of the rod (on the M59, and if I remember rightly)

I recall that tilting the tractor with one stabilizer leg wasn't enough to get the BH to swing under gravity alone. To move it I had to lightly bounce the boom cylinder at the same time. Bouncing creates a hydraulic shock wave has a pressure many times higher than system normal. Maybe that helped?

Also, on the M59 - and probably on the L's as well - the swing circuit also provides the flow to any optional rear remotes, so if you have rear remote QCs they would make a convenient test point for swing flow & pressure.
rScotty

 

[Smokeydog]

Likewise “bounced” other circuits to help restore lost power to boom and swing functions. The swing and boom circuits being the biggest rockers to cause pressure surges.

My M59 didn’t come with backhoe hydraulic quick disconnects because it was sold as a tractor loader. Removing pipe plugs and installing flat face disconnects on both tractor and backhoe was easy enough. Did note the six threaded factory connections I used had been sealed using Teflon tape. Usually a bane of hydraulic systems. Smallest pieces of tape can mess with valves. Sealed new connections with hydraulic thread sealant paste. Hopefully the hydraulic circuits get flushed out, trash gets collected by the filters and the monetary loss of control events will diminish over time. Totally wishful thinking and guessing.

Still frustrating. If it wasn’t for TBN contributors I would only have the dealer to advise and that can get expensive fast. Haven’t heard of a Kubota service remedy yet.

 

[rScotty]

Likewise 澱ounced other circuits to help restore lost power to boom and swing functions. The swing and boom circuits being the biggest rockers to cause pressure surges.

My M59 didn稚 come with backhoe hydraulic quick disconnects because it was sold as a tractor loader. Removing pipe plugs and installing flat face disconnects on both tractor and backhoe was easy enough. Did note the six threaded factory connections I used had been sealed using Teflon tape. Usually a bane of hydraulic systems. Smallest pieces of tape can mess with valves. Sealed new connections with hydraulic thread sealant paste. Hopefully the hydraulic circuits get flushed out, trash gets collected by the filters and the monetary loss of control events will diminish over time. Totally wishful thinking and guessing.

Still frustrating. If it wasn稚 for TBN contributors I would only have the dealer to advise and that can get expensive fast. Haven稚 heard of a Kubota service remedy yet.

That's right. I remember you doing that. BTW, what thread were those adapters you used to replace the pipe plugs in threaded factory connections in the rear of the Kubota housing? I suspect that they should be BSPT x ?

I sure wish that the Kubota parts manual followed normal international convention by calling out threads, hose size, O-ring dims. in their part books along with the part number. There is a place for the specs right there in their parts book; Kubota got that part right. They even left the space blank next to each part; they just didn't put in the information. I fill in add those specs in when I think of it.
rScotty

 

[Smokeydog]

The pipe plugs looked like tapered NPT pipe plugs, one 3/8” and two 1/2”. Checked the thread pitch. Male to male nipples installed the same into the line distribution blocks. 1/2” pipe threads of BSPT and NPT are so similar that they fool experts. I’m no expert. Hope I didn’t mess up. No leaks yet.

Have encountered BSPT on other hydraulic fittings and even BSPT on hydraulic grease fittings on my other Kubota tractors. Been careful not to cross thread.

 

[avc8130]

I'm still not so sure about what could be going on here. A coworker has an L39 and has also been experiencing this problem along with me for close to a decade. Eventually he decided to dig in and try to solve it.

Switching the controls from the stick to the stabilizer didn't make the problem go away.

He dug into his cylinders and what he found is quite concerning. One of the cylinder shafts had actually broken and the piston was just free-floating in the cylinder.

Our theory is that when that cylinder was extending the oil would force the piston back into contact with the shaft and it would move. When the cylinder was retracting, the other cylinder must have been performing all the function. We think what happens might be that the piston gets to a point where it is not attached to the shaft, and is very close to if not partially blocking the port in the cylinder. Then the fluid can flow right past the piston and you get no motion. Gravity and bumping might create a small vacuum or other force that moves the piston into a spot it can be acted on by the fluid and the hoe "fixes" itself...until the next time.

He sent me a picture of what he found, and a crude sketch of the theory.



ac

 

[avc8130]

Bueller?

 

[rScotty]

Bueller?

Well, I had to look up "Bueller" online. It's not a rural or western term. I'd never heard it. Weird.

"Google Search: What does it mean to say Bueller?
Goodle Answer: Bueller: Interjection. Expression used to convey waiting for a response when there is none."


But on to the cylinder. I am very impressed at your coworker's theory. I like the guy's go for it attitude on diagnosis. Plus I never did like the "piece of crud stuck somewhere" theory. It just didn't make sense given the velocity of that hot hydraulic oil.

But I guess I'm also surprised that we haven't heard of it here on TBN. Did he just find this out? Has he posted it anywhere? What was the response there?? Did he contact Kubota? What did they say??

This seens to be the first time anyone has actually gone after solving this TBN problem and I'm stunned by what he found. And as I think about it it brings up even more questions.

What he found could be huge! We already know that Kubota had a unpublished recall for some of their TBN boom cylinders that came apart internally. I was the recipient of a replacement boom cylinder after the warranty was expired - and no questions asked. Could there be any connection? Is this the same cylinder mfg? Did Kubota make those cylinders or were they outsourced.
And what's your co-worker going to do? Has he talked to Kubota? That would be my first move. The previous factory cylinder replacement was NOT a publicised recall.

Then there's the mechanical questions....What really happened inside the cylinder and why? Did that shaft break or did a nut come loose? Can't tell from the pictures. Can he just screw it back together? How is the shaft affixed to the piston? Is there damage to the inside wall? Is Kubota interested?

And we need to figure out a simple way to tell if other Kubota TLBs have had the same thing happen. Some kind of test we all agree about that can be done without having to take the cylinder out and apart. Any ideas on that? What's simple & 100%?
rScotty

 

[avc8130]

Well, I had to look up "Bueller" online. It's not a rural or western term. I'd never heard it. Weird.

"Google Search: What does it mean to say Bueller?
Goodle Answer: Bueller: Interjection. Expression used to convey waiting for a response when there is none."


But on to the cylinder. I am very impressed at your coworker's theory. I like the guy's go for it attitude on diagnosis. Plus I never did like the "piece of crud stuck somewhere" theory. It just didn't make sense given the velocity of that hot hydraulic oil.

But I guess I'm also surprised that we haven't heard of it here on TBN. Did he just find this out? Has he posted it anywhere? What was the response there?? Did he contact Kubota? What did they say??

This seens to be the first time anyone has actually gone after solving this TBN problem and I'm stunned by what he found. And as I think about it it brings up even more questions.

What he found could be huge! We already know that Kubota had a unpublished recall for some of their TBN boom cylinders that came apart internally. I was the recipient of a replacement boom cylinder after the warranty was expired - and no questions asked. Could there be any connection? Is this the same cylinder mfg? Did Kubota make those cylinders or were they outsourced.
And what's your co-worker going to do? Has he talked to Kubota? That would be my first move. The previous factory cylinder replacement was NOT a publicised recall.

Then there's the mechanical questions....What really happened inside the cylinder and why? Did that shaft break or did a nut come loose? Can't tell from the pictures. Can he just screw it back together? How is the shaft affixed to the piston? Is there damage to the inside wall? Is Kubota interested?

And we need to figure out a simple way to tell if other Kubota TLBs have had the same thing happen. Some kind of test we all agree about that can be done without having to take the cylinder out and apart. Any ideas on that? What's simple & 100%?
rScotty

Haha, old reference to Ferris Bueller's Day Off movie.

My coworker isn't a forum type. This happened to him last year. No reason to contact Kubota as the machine is 10+ years old. He just brought it to a local hydraulic shop and they fabricated a new shaft. $1000 later...

The shaft failed. The nut was still attached to the threads, but the threads broken from the shaft.

Well, I'm going to take my left cylinder apart. My L45 refuses to swing left now. If I find the same thing he found, I'm gonna guess everyone with the intermittent "no swing" probably has a similar issue.

ac

 

[avc8130]

rScotty,

Does anyone have any better explanation for what's going on?

I could pull the relief valve at the control for the left swing direction, but I think it's working just fine. I can hear fluid flow through the valve at partial activation, then once I get past ~33-50% of lever movement the hissing sound of flowing fluid goes away...likely because it's just flowing through the system freely?

ac

 

[rScotty]

Haha, old reference to Ferris Bueller's Day Off movie.

My coworker isn't a forum type. This happened to him last year. No reason to contact Kubota as the machine is 10+ years old. He just brought it to a local hydraulic shop and they fabricated a new shaft. $1000 later...

The shaft failed. The nut was still attached to the threads, but the threads broken from the shaft.

Well, I'm going to take my left cylinder apart. My L45 refuses to swing left now. If I find the same thing he found, I'm gonna guess everyone with the intermittent "no swing" probably has a similar issue.

ac

Wouldn't it be better to try a test first? There are a couple of problems with your coworker's theory and the posted pictures. That may be because they are still in process. I haven't looked at the hydraulic flow map, but I'm not sure that his theory with those pictures explains why the other cylinder isn't able to do all the work.

His drawings are beautiful. But I think if we were to move the position of the "extend port" more toward the center of the cylinder - slightly to the center of where he shows the piston seals, then his theory makes more sense. In that way it may be that the loose piston is able to somehow block some of the flow.

Revising the drawing also makes an alternate theory is possible for him. In that one, a loose piston might be able to move all the way to the end of the cylinder which allows the incoming flow to hydraulically lock both swing cylinders. I would have to look at the hydraulic schematic flow diagram to see if that is possible. I'm not the world's best at deciphering a hydraulic schematic - still studying it - so if anyone is then let me know.

But I think that if either of those theories are true, then simply capping the appropriate hose and cylinder on your tractor would make the remaining cylinder able to work again and confirm the problem.

Oh....also fitting an inexpensive inline hydraulic on/off valve would also do the same thyying.
rScotty

 

[rScotty]

I'm trying to remember who it was who reported that their new M59 (I think it was an M59) would only swing half as fast as he expected. In a thread a few months ago, he timed his and then I timed mine, and sure enough his backhoe is swinging only half as fast as mine for a full swing side to side at the same RPM.

I wonder if he is only working on one swing cylinder.... Or Am I?
rScotty

 

[avc8130]

Here are the hydraulic diagrams from the Kubota service manual.

 

[avc8130]

rScotty,

Does your hoe have decent power on swing? Can you pick the machine up and move it side to side? Can you push up against a tree and actually feel it? Mine is pretty weak...and so was my coworkers.

The pictures I made, they are just hacks with MS Paint off the best cross-section I could find on the internet. The exact placement of the ports and dimensions for the components may or may not accurately represent the Kubota.

I think the next step for me is to plumb around the left cylinder and see if it works.

ac

 

[rScotty]

rScotty,

Does your hoe have decent power on swing? Can you pick the machine up and move it side to side? Can you push up against a tree and actually feel it? Mine is pretty weak...and so was my coworkers.

The pictures I made, they are just hacks with MS Paint off the best cross-section I could find on the internet. The exact placement of the ports and dimensions for the components may or may not accurately represent the Kubota.

I think the next step for me is to plumb around the left cylinder and see if it works.

ac

Yes, mine has decent power in swing. No problem moving the whole tractor around with the backhoe; including swing. In fact, I do more sidesweeping than I should just because the swing works so well. But I'm still suspicious. After all, I did have that episode where it wouldn't swing one way even if it was years ago. I am fairly gentle on the backhoe. I run at half rated rpm and don't slam it around.

There are good M59 hydraulic schematics in good resolution in my shop manual.....although the M59 might not be the same as the L45?
I am a novice at reading hydraulic schematics. Just learning.
For anyone interested, FluidPowerWorld.com has an online tutorial on hydraulic symbology. Start with lesson 101.

Agree that plumbing would be a good diagnostic step. Or just put a manual valve inline. Surpluscenter.com has 7000+psi ball valves in the $20 range.

What is you feeling on why your co-worker's shaft broke? Only thing I can think of would be a tension failure.

 

[avc8130]

Yes, mine has decent power in swing. No problem moving the whole tractor around with the backhoe; including swing. In fact, I do more sidesweeping than I should just because the swing works so well. But I'm still suspicious. After all, I did have that episode where it wouldn't swing one way even if it was years ago. I am fairly gentle on the backhoe. I run at half rated rpm and don't slam it around.

There are good M59 hydraulic schematics in good resolution in my shop manual.....although the M59 might not be the same as the L45?
I am a novice at reading hydraulic schematics. Just learning.
For anyone interested, FluidPowerWorld.com has an online tutorial on hydraulic symbology. Start with lesson 101.

Agree that plumbing would be a good diagnostic step. Or just put a manual valve inline. Surpluscenter.com has 7000+psi ball valves in the $20 range.

What is you feeling on why your co-worker's shaft broke? Only thing I can think of would be a tension failure.

My feeling is that owners of the L39/L45/M59 all seem to experience this mysterious symptom where the backhoe stops swinging in one direction. For all of us, gravity motion and "bumping" has had some success "fixing" it. My coworker had the same experience, but refused to believe that this mysterious "solution" made any sense. Se he investigated and found stuff had actually failed. NO ONE else has any conclusive resolution to this phenomena.

A tension failure would make sense, but what would cause it? I'm pretty sure the hoe hits the stabilizers long before it runs out of swing travel on the cylinders?

 

[rScotty]

My feeling is that owners of the L39/L45/M59 all seem to experience this mysterious symptom where the backhoe stops swinging in one direction. For all of us, gravity motion and "bumping" has had some success "fixing" it. My coworker had the same experience, but refused to believe that this mysterious "solution" made any sense. Se he investigated and found stuff had actually failed. NO ONE else has any conclusive resolution to this phenomena.

A tension failure would make sense, but what would cause it? I'm pretty sure the hoe hits the stabilizers long before it runs out of swing travel on the cylinders?

My hat is off to him for taking his cylinders apart and having a look. Right or wrong, so far it is the only positive mechanical information that we have.

If not a solid stop, how about Hydraulic Shock? Given high RPM and a load in the bucket, could suddenly reversing the swing with the control levers create enough tensile force on that rod end to cause the failure?

And looking at the cylinder rod, we have to wonder what mods to piston and rod would make sense to increase the strength of the threaded portion? I'm sure your co-worker put some thought into that. What conclusions?

A shock-damping damping reservoir on a T in the pressure feed line would be another solution.

I will be fascinated to hear what you find in yours.

rScotty