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?