Backhoe Side to Side -- Stuck?

[GeneSimm7]

I had something similar happen with my FEL and it turned out to be low in Hyd fluid.

 

[ppopsu01]

Another thought is , could the hose be breaking down internally, allowing flow in one direction, but not to return. Kind of like a check valve. Ive seen this happen on brake hoses, causes the brakes to stay on and not release the caliper.

 

[rScotty]

Any luck with the trick described above, or other cures? I have a L39 that does the same thing, except the that powered right swing has not returned.

Apparently there are several different symptoms that can go wrong with the swing circuit. The swing circuit relief valve (there are 2) is the most common suspect.
Replacing the swing reliefs is at most a half hour job.
Having a spare swing releif valve for the older TLBs - L39,L45,M59 - makes sense.

 

[Old Shas]

My mystery is solved!

I could swing the boom to the left but not to the right. If the tractor was on a slop leaning right, the boom would slowly move to the right indicating the pressure relief valve was open. Many people have suggested shaking the backhoe with it tilted the other way using the outriggers fixed their problem which would apparently unstick the pressure relief valve. I tried that for 10 minutes and high RPM's, low RPM's, using the outriggers to shake the tractor left and right, shaking the boom while trying to swing it and nothing I did fixed the problem.

In my research, I found the pressure relief valve is a pilot style where this is a small hole that left the system pressure bypass the pressure relief valve and put pressure on the backside of the valve forcing it shut. There is a small lightweight spring that adds a few pounds of pressure to the system pressure helping keep the main pressure relieve valve closed. When the pressure becomes out of balance between the flow and the relief side, ie more pressure on the flow side than on the relief side it overcomes the power of the spring and opens the main relief valve. That way a small spring con control a large amount of pressure and flow. One video I found likened it to a 12v relay opening and closing a 480v circuit.

On my M59 BT1200 backhoe, the control valve spool was moving fine. I removed the plate and top shroud around the backhoe hydraulic control valve. In tracing the hydraulic hoses, I found the topside of the valve was flow to move the boom left (from the seat in the tractor) and the bottom side of the valve would have flow to move the boom right. So I knew I had to remove the top pressure relief valve. I made sure there was no pressure in the system by putting the tractor on the ground and locking the boom in the up position. I took an adjustable wrench and removed the top pressure relief valve. They use an o-ring to seal it so it was not hard to remove.

I compared the pressure relief valve (7K521-63712 per Kubota Tractor BT1200/BT1200V B21001 Control Valve [Component Parts] ## [Bt1200] | Kubota Tractor) and compared it to the new/spare boom pressure relief valve (7K521-63732) I had. The pilot has a pin at the bottom with a lightweight spring that keeps it closed and on the valve I removed, the pin was stuck open. The pin on the spare valve moved freely and it only took a small amount of pressure/pushing to open it.

On another thread, a person said Kubota told them the pressure relief valve was not serviceable. If so, shame on Kubota. I took off the assembly that holds the pin in place and sure enough inside was the main valve (looked like a cup) which was held in place by a larger spring, the pin which went through the center of the cup which was also held in place with a smaller spring. In my case, for some reason, the small spring had jumped the shoulder on the pin that would hold the pin closed and therefore was no longer pushing on the pin. Since the pin was stuck open, the main valve (cup w/ larger spring) would open and all of the system pressure would flow back to tank.

I was able to remove the small spring and reseat it on the pin shoulder and reassemble the pressure relief valve. Now the pin moves freely and I could easily push it the circuit open with my finger just like the new spare unit I had. I put it back on the tractor and sure enough, the backhoe is as good as new. The story here is that if the pressure relief valve is stuck open or the spring or the small pin is broke, your system pressure when trying to swing the boom will just go right to the hydraulic tank. The good news is that it is very easy to remove, disassemble and inspect. In my case, if I had know, I could have fixed with just 2 wrenches in 10 minutes. Now I know and will not be afraid to remove the pressure relief valves and take them apart if needed.

Message to Kubota: The swing valve pressure relief valve is $650 to replace. WTF. There is likely little that can wear or break other than the o-rings, the springs, the pilot pin or the main pressure relief cup. I cannot see any of those items costing more than $10 yet there is no rebuild kit or replacement parts available. What a major miss to help owners maintain their equipment cost effectively. I suppose an owner could try to find similar springs if one broke but why have to. Shame on Kubota if they cannot make these parts available to their equipment owners!

Below are my photos and I have videos as well if someone would like me email them.

Hope this helps others out there and I really appreciate the folks on this forum and the information I was able to gather to get me moving in the right direction! Be sure to use the swing safety pin and the boom safety latch when working around or transporting the tractor. It is very clear to me know that a small issue with the pressure relief valve means hundreds of pounds of backhoe will be in motion with no control pressure check to keep it in place so be safe.

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As good as new!

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What an excellent write up,
and spectacular photos.
Thanks for sharing this.

 

[gbutts]

I have a B26 and I haven’t encountered this problem (yet!). I’m unsure if the hardware has a different design to the M59.

Either way, an excellent thread with great information. Thanks to all who contributed - bookmarked for future reference.

 

[Zork]

I was digging a hole with my Kubota m59 Backhoe and suddenly it went to the right (when facing rear) as far as it could go, and is holding itself there touching my stabilizer.

I cannot reposition it.

I came back the next day and it had no problem, started up centered, and it stayed there for my next 1-2hr project.

Fast forward a day later I needed to go do another project and I get 100' away driving and once again it goes far right max position, and now it won't center or let me center it.

I popped off the cover to see the controls and nothing is sticking or getting hung-up that I can see.


Position sensor? Valve? Dirty Screen? I have no clue what this could be but it seems to be either "on" or "off" no in-between bleeding off causing it to slowly move.

Do you see Teflon tape on any of your fittings? Your system and that valve could be contaminated. [Nevermind]

 

[heading westward]

Thank you so much for sharing this information. I have a L45 that occasionally would not let backhoe swing left as though someone unhooked the linkage btwn the handle & valve. You could notice the backhoe boom just “twitch” ever so slightly to the left then nothing. It only happens once or twice about every 20 hrs of backhoe use. It returns to normal very quickly but is very annoying. I bought the unit used and it appears the original owner had the same issue because there are witness marks on the swing cylinders showing that they have been apart. I can guarantee they were chasing the same problem that never got fixed.

 

[rScotty]

Thank you so much for sharing this information. I have a L45 that occasionally would not let backhoe swing left as though someone unhooked the linkage btwn the handle & valve. You could notice the backhoe boom just “twitch” ever so slightly to the left then nothing. It only happens once or twice about every 20 hrs of backhoe use. It returns to normal very quickly but is very annoying. I bought the unit used and it appears the original owner had the same issue because there are witness marks on the swing cylinders showing that they have been apart. I can guarantee they were chasing the same problem that never got fixed.

Do you do anything special to make it return to normal?

If it is unpowered to the left, have you tried the technique of moving the swing all the way to the right, then fully raising the right outrigger, extending the hoe, and rapidly moving the swing valve as gravity swings the boom to the left?

That's how I get our M59 working again.

rScotty

 

[heading westward]

Do you do anything special to make it return to normal?

If it is unpowered to the left, have you tried the technique of moving the swing all the way to the right, then fully raising the right outrigger, extending the hoe, and rapidly moving the swing valve as gravity swings the boom to the left?

That's how I get our M59 working again.

rScotty

When the problem happens I move the left swing handle left to right several times and the boom’s swing functions returns to normal. On a couple of occasions I noticed that if the LH side of the machine is leaning down (RH side if operating the backhoe) when swinging to the right and I let go of the controls the boom will keep swinging until it physically can’t. This takes place just before the control stick has no input attempting to swing left. Only on a hand full of occasions has the swing not returned to functioning normal. I’d have to shut the machine down and restart or do other backhoe functions then it’ll return to normal. I have yet to try using the stabilizers to lean the tractor 1 way or the other to see if that makes a difference when the problem occurs.

 

[TWD]

I should have updated this a month ago or more now...

I took apart the entire thing as someone pictured (thank you so much), ran the springs\misc parts through my ultrasonic cleaner, re-assembled, and it works... mostly.

However... I still do not have full pressure to one side... for example I can't use the backhoe to lift the rear end over a ditch in one direction, but I can the other direction with so much force I'd throw myself out if not paying attention or running to high RPM when doing so

I've put about 60hrs on the backhoe since then 100% use of removing stumps and now my thumb cylinder is leaking around the cylinder rod (already replaced on my dipper), and in addition to that my main cylinder is leaking around the threads... hoping that's just needing to be tightened up but it's a bit upsetting to see so much issues in something that was barely used for years until now. (It was used to lift and move things monthly since I've owned it, and remove a stump or 2, but now I'm using it for hours on end.)


Question -- For those of us who had this problem do you operate the backhoe for hours on end and\or in high temperatures? I noticed I was getting really hot when outside air temp was only 70-75 and it was from the AUX hydraulic lines to the left (not in use) radiating heat... I cleaned out my hydraulic cooler fins and ran it for 2-3hrs and the AUX lines never got hot that I felt them!! That was nice. Does Kubota have an "overheat" hydrlauic fluid warning? Or how do you know it's overheating? (I personally can tell after 2-3hrs I start to smell the fluid, not burn, its just "its heated up now I smell it.) I'm just curious if i'll know (alarm) if I overheat it, or if not, and if not, I'll change all fluids.

 

[rScotty]

I should have updated this a month ago or more now...

I took apart the entire thing as someone pictured (thank you so much), ran the springs\misc parts through my ultrasonic cleaner, re-assembled, and it works... mostly.

However... I still do not have full pressure to one side... for example I can't use the backhoe to lift the rear end over a ditch in one direction, but I can the other direction with so much force I'd throw myself out if not paying attention or running to high RPM when doing so

I've put about 60hrs on the backhoe since then 100% use of removing stumps and now my thumb cylinder is leaking around the cylinder rod (already replaced on my dipper), and in addition to that my main cylinder is leaking around the threads... hoping that's just needing to be tightened up but it's a bit upsetting to see so much issues in something that was barely used for years until now. (It was used to lift and move things monthly since I've owned it, and remove a stump or 2, but now I'm using it for hours on end.)


Question -- For those of us who had this problem do you operate the backhoe for hours on end and\or in high temperatures? I noticed I was getting really hot when outside air temp was only 70-75 and it was from the AUX hydraulic lines to the left (not in use) radiating heat... I cleaned out my hydraulic cooler fins and ran it for 2-3hrs and the AUX lines never got hot that I felt them!! That was nice. Does Kubota have an "overheat" hydrlauic fluid warning? Or how do you know it's overheating? (I personally can tell after 2-3hrs I start to smell the fluid, not burn, its just "its heated up now I smell it.) I'm just curious if i'll know (alarm) if I overheat it, or if not, and if not, I'll change all fluids.

Keep up the good Science! We are slowly accumulating information. We will figure this out someday; I've no doubt. And it is fun to be able to work on something that is so technical that
Kubota couldn't make any progress on it.
To answer your question... Yes, I have noticed that the swing function does change at high temperatures. After hours of operation there is sometimes a little change in how the swing responds to the lever command - particularly at the very extreme of the swing. It occurs as a slight hesitation between the lever movement and the swing movement. Normally they are simultaneous. I see this on the left swing more than the right, but that might just be because I use that side for small movements and so it is more obvious.

I don't know if there is a hydaulic fluid heat warning. The JD310 has a converter temperature gauge, but not the M59.

One thing I have encountered from reading & study is the idea that that trans/hydraulc fluid differs from motor oil in how it ages with temperature. That seems to be common knowledge, but just how and how much is harder info to find.

Some literature mentioned that only a very few high temperature excursions might drastically reduce the lubricity. However, the aging was said to be very much non-linear and I haven't seem any real data.

I may go clean off those radiators today and maybe put some temperature gauges on the hydraulic lines. Will keep us posted.
rScotty

 

[Zork]

Try switching out the cylinders with each side and see if your problem changes with the cylinder. That should indicate that fluid is leaking past the packing when it's hot.

 

[rScotty]

Snip

I may go clean off those radiators today and maybe put some temperature gauges on the hydraulic lines. Will keep us posted.
rScotty

Today I cleaned the radiator cooling fins for engine and hydraulics. It was about like I expected, having not cleaned them in about 12 years or more. Anyway, just for fun info I also installed a gauge to compare hydraulic fluid temperatures entering and leaving the fluid cooling radiator. The temperature senders are external. The senders are just taped to the hoses after being coated with thermal mastic and insulation. Be interesting to see if this simple approach tells us anything.

I've got some BH digging to do next week, so that will give the gauge a workout.
Normally, most of my backhoe work is picky rock wall construction done at just above idle - and I may mess with a series of footlocker size rocks for an hour before satisfied with how they fit. When doing that type work there is not a lot of backhoe motion or high flow rates. But the work is constant and the sun hot. Even with that light work I can feel heat from the backhoe. When I park it, the main boom cylinder is uncomfortable to hold onto, but ok just to touch.
rScotty

 

[TWD]

Today I cleaned the radiator cooling fins for engine and hydraulics. It was about like I expected, having not cleaned them in about 12 years or more. Anyway, just for fun info I also installed a gauge to compare hydraulic fluid temperatures entering and leaving the fluid cooling radiator. The temperature senders are external. The senders are just taped to the hoses after being coated with thermal mastic and insulation. Be interesting to see if this simple approach tells us anything.

I've got some BH digging to do next week, so that will give the gauge a workout.
Normally, most of my backhoe work is picky rock wall construction done at just above idle - and I may mess with a series of footlocker size rocks for an hour before satisfied with how they fit. When doing that type work there is not a lot of backhoe motion or high flow rates. But the work is constant and the sun hot. Even with that light work I can feel heat from the backhoe. When I park it, the main boom cylinder is uncomfortable to hold onto, but ok just to touch.
rScotty

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Yeah, that's my usual workload the last 13 or so years, only in the last 2 or 3 have I really started digging with it or playing logger moving large\heavy logs.

Can you link to that 2 probe temp device? I want to rig up something like that as well... I have a new cooler here too, just not sure how\where I would plumb it for additional cooling, but it sure seems like when working the backhoe (or even FEL) it's needed... the FEL cylinders get so hot you can't touch them just moving dirt after a couple hours of non-stop use.

Sounds like I'll be changing my fluid with the filters this year just to be sure all fresh after all the new leaks, and issues that popped up after heavy use of the backhoe.

 

[Smokeydog]

Today I cleaned the radiator cooling fins for engine and hydraulics. It was about like I expected, having not cleaned them in about 12 years or more. Anyway, just for fun info I also installed a gauge to compare hydraulic fluid temperatures entering and leaving the fluid cooling radiator. The temperature senders are external. The senders are just taped to the hoses after being coated with thermal mastic and insulation. Be interesting to see if this simple approach tells us anything.

I've got some BH digging to do next week, so that will give the gauge a workout.
Normally, most of my backhoe work is picky rock wall construction done at just above idle - and I may mess with a series of footlocker size rocks for an hour before satisfied with how they fit. When doing that type work there is not a lot of backhoe motion or high flow rates. But the work is constant and the sun hot. Even with that light work I can feel heat from the backhoe. When I park it, the main boom cylinder is uncomfortable to hold onto, but ok just to touch.
rScotty

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That would be a good test. When mowing I have clear the radiators and screen several times a season. Curious what temperatures might be seeing. That’s usually the hottest I see the tractor.

Backhoe boom cylinder can get hot. About 180-190 degrees per millwright hand test.

 

[rScotty]

I ran the hoe today for about an at our normal BachHoe RPM for tricky work... around 1200/1500 RPM. We were digging up pipes that I didn't want to hit. Air temperature here was about normal summertime....roughly 80*F in the shade, and much, much hotter at 7000 feet in dorect sumlight.
Checking the fluid temperature after an hour of easy digging, the fluid entering the fluid coolant radiator was 122*F and exit temperature 111*F.

Here is the temperature guage I used. Interesting fact: the US-made plastic tape that I used to mount the sensors was bought at Ace Hardware where two rolls of tape cost about the same as the complete thermocouple gauge built in China, sold on Amazon, and shipped to my doorstep.
rScotty

 

[Smokeydog]

Like your experiment. Impressed how clean and new looking your tractor is. Mine was battle worn before I got it and have added a few scars. Think my heat exchanger is bare aluminum, not painted (2014).

To try to replicate your results, what heatsink mastic did you use?

On your heat exchanger one side has band hose clamps, the other has wire. Was this from a repair? Which side is inlet/outlet?

Haven’t figured out the mounting the instrument case in my application yet. Need to read real time from the operator position while bushhogging, tree cutting and carrying. Blank center console area probably the obvious spot. Longer leads necessary. Might have to go your route in China instrumentation as my Fluke thermometer cost >$10X and don’t want to trash it. Thermocouple readings on radiator, engine oil, hydraulic filter(s), under hood would all be interesting. Beginning to look like a science experiment from my past job. Then trying to improve heat transfer with fans and or additional exchangers could be better measured.

 

[Zork]

My tractor and backhoe does not have an oil cooler and a few times early on during heavy use I could smell warm oil. My transmission is gear and not hydro. For those of you with a cooler and elevated temps, can you install a remote unit in the return line with a fan in the open space at/below/between at the backhoe 3pt, or subframe connection?

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www.surpluscenter.com

 

[rScotty]

Like your experiment. Impressed how clean and new looking your tractor is. Mine was battle worn before I got it and have added a few scars. Think my heat exchanger is bare aluminum, not painted (2014).

To try to replicate your results, what heatsink mastic did you use?

On your heat exchanger one side has band hose clamps, the other has wire. Was this from a repair? Which side is inlet/outlet?

Haven’t figured out the mounting the instrument case in my application yet. Need to read real time from the operator position while bushhogging, tree cutting and carrying. Blank center console area probably the obvious spot. Longer leads necessary. Might have to go your route in China instrumentation as my Fluke thermometer cost >$10X and don’t want to trash it. Thermocouple readings on radiator, engine oil, hydraulic filter(s), under hood would all be interesting. Beginning to look like a science experiment from my past job. Then trying to improve heat transfer with fans and or additional exchangers could be better measured.

I've no idea what's in my old box labeled as 3M Thermal Mastic. It feels grease-based. If so my guess is that it is pre-silicon and probably for low temp AC in my old '72 Chevy PU rather than hi temp tractor hydraulics. I used only the slightest amount because I was concerned that any mastic leakage would saturate my 1/8 " think insulation layer on top of the heat sensor bead. The heat sensing bead is tiny - about 0.050" diameter. To prevent seepage I separated the insulation from the bead & mastic with two layers of silicon and vinyl.
Doing it again, I would use a RTV type of mastic that cures flexible. Or none at all.

You've a good eye on the hose clamps. I didn't even notice the difference until you pointed it out. My excuse is I was racing the dark..... This M59 is one of the early ones and the system is all stock, so I looked in the M59 Parts Manual and sure enough they show hose clamps on the left side - which the parts book says is the O/C return line. And on the other side - labeled in the book as the HST return side - they show double wire band clamps. Yes, that's right: both lines are labeled as returns for different hydraulic circuits. I'm mystified.

The Shop Manual is not much help to me. Either the section that covers the oil cooling radiator is poorly written or I am missing something. I wonder if the M62 Shop Manual is any better?
My guess is the person writing it did not fully understand how the cooling functioned. Either that, or the cooling was added afterwards. The latter is a distinct possibility.

Looking at the hydraulic schematic, my perception is that the oil cooler does not cool all of the hydraulic oil flow that is circulating. It looks to cool a percentage in a bypass system working with the power steering circuit.

It might be worth instrumenting some other point than the stock oil cooler.
rScotty

 

[Smokeydog]

I would think lower temperature probe would identify the outlet. I wasn’t exactly sure which side either.

Thinking temperature under 200F normal. Maybe even 240F. People are poor thermometers so your data is way better. Spot checking backhoe boom and FEL lift cylinders with non contact IR thermometer could add reference data. There is value in information. I know enough to be humbled by my ignorance.

The first gen B20 had a flat plate hydraulic oil cooler in front of the radiator. Newer B26 uses just convoluted metal tubing.

Hot smell of hydraulics is a symptom of air entrainment usually on suction side. Any external leaks can also leak air and contamination back into a hydraulic system. Unwanted air in any hydraulic system causes overheating and poor performance. People concerned about running hot should troubleshoot the easy stuff first.

All the backhoes I have run have got hot with heavy use. Smaller ones you tend to be closer to the cylinders.