Backhoe Side to Side -- Stuck?

[Smokeydog]

Also have intermediary loss of power swing left and boom down on my 2013 M59. Suspect a spec of debris. Have not taken the time to disassemble to check as the problem is transitory. Interested to any solution.

Definitely use your swing lock for road transport.

 

[rScotty]

Hello to all the M59 guys out there....

I'm the guy who originally posted those illustrations in messages 16 & 18. Yes, I agree with OldnSlow that the most likely culprit is some crud, bubble, or malfunction in the RELIEF VALVE for the swing circuit (shown below). Not in the Load Check valve.

The M59 control valve assembly uses a number of these identical RELIEF VALVES in all the power circuits. And yes, that multiple use relief is one of the main hydraulic features that was completely re-designed in the different control valve for the M62.

Originally I was so sure that valve was responsible for the swing problems that I ordered a couple of those relief valves just to have them on hand. They are used in pairs, and cost half back then what they do today. But I never used them, because while waiting for them to arrive, I figured out that I might be able to purge the relief valve using gravity to swing the boom...
That was a ong shot and only theoretically possible, but even a blind pig finds an acorn now and again. And to my amazement it worked! It has worked twice now for me and countless times for others. I've explained it before, maybe others can explain their version of how to do it and we can combine forces.

If it hadn't worked, my next move would have been to simply remove those RELIEF VALVES, disassemble, clean, and replace. They look serviceable, though since I never did I don't know for sure.

rScotty

 

[loggin]

Very interesting information here!! Trying to understand a little more. rScotty, is that diagram for the BT1200? Looks similar to the spool valve for the BH92 that I have. I have not encountered this swing issue as of yet but am interested in finding out more. Seems there have been some BH77 swing issues but can't find any good explanations for fixes so far. Please keep the ideas coming!!

 

[rScotty]

Good question about the other backhoe models. I don't know if they have a similar control valve setup or not. Real interesting question you bring up about that BH77 and other add-on Kubota backhoe models though..... I don't know the answer and never thought about it. I can't remember any problems being reported here on TBN with the other add-on implement hoes - or even with the factory hoes on other TLBs for that matter. I may have just missed them.

That diagram you asked about in message #22 is one I pulled directly from Messicks' parts catalogue online so we could also see the updated price for the relief valve. Messicks has it listed under BT1200 parts for the M59 and my guess is that they got that right.
Why do you ask? Did you see any difference?

The other earlier diagrams in earlier messages came from my M59 shop manual backhoe supplement, so I have more confidence they are for our M59s.

I hope you do take those relief valves apart and give us a report... although I completely understand if you find the same easy fix others have and never get to it.
Maybe Kubota will help us with this. Their redesign of that BH control valve for the M62 makes me think they may be paying attention.

And I am going to be religious about using the swing lock during transport from now on.
That is something I have not always done in the past.

rScotty

 

[m59owner]

Air bubble would not cause a relief to fail but a piece of contaminate certainly will especially if that is the style of relief that also has anti-cavitation check built in. The check opens at real low crack pressure to draw oil from tank line to help keep an over running cylinder full of oil. Then if check sticks open it prevents the relief from building pressure.

Thanks oldnsio. Good to know. Long workdays this week so may not get to my shake and wiggle attempt until the weekend.

 

[m59owner]

I have the spare pressure relief valved for the boom hydraulic control valve when that acted up a couple of years ago and will take that out of the bag for some close up pictures this weekend. I may still remove the swing relief valve to compare even though the 2 are different part numbers. Maybe they are just set to relief pressure at different points. Will keep the group posted.

 

[m59owner]

If you take the valve out to check for broken gasket\o-ring please take pics as you go and share

It appears it's not too much effort, and that's my plan to tackle in the coming weekend.

Also, did you check your hydrualic fluid level? I did, mine was at the bottom line I'm going to top it off and maybe get lucky it was air in the line... probably not, but hey, worth it

For reference, I had checked the fluid level the day before and all was good with no leaks to draw it down. Will recheck this weekend again but expecting it to still be fine. I hope to take the problem relief valve out to compare to the spare one I have for the boom once I get time. I will take some pics to share.

 

[loggin]

Good question about the other backhoe models. I don't know if they have a similar control valve setup or not. Real interesting question you bring up about that BH77 and other add-on Kubota backhoe models though..... I don't know the answer and never thought about it. I can't remember any problems being reported here on TBN with the other add-on implement hoes - or even with the factory hoes on other TLBs for that matter. I may have just missed them.

That diagram you asked about in message #22 is one I pulled directly from Messicks' parts catalogue online so we could also see the updated price for the relief valve. Messicks has it listed under BT1200 parts for the M59 and my guess is that they got that right.
Why do you ask? Did you see any difference?

The other earlier diagrams in earlier messages came from my M59 shop manual backhoe supplement, so I have more confidence they are for our M59s.

I hope you do take those relief valves apart and give us a report... although I completely understand if you find the same easy fix others have and never get to it.
Maybe Kubota will help us with this. Their redesign of that BH control valve for the M62 makes me think they may be paying attention.

And I am going to be religious about using the swing lock during transport from now on.
That is something I have not always done in the past.

rScotty

The reason I asked was because I was fumbling around on Messicks website to look at the different spool valves of other backhoes and could not find the diagram you posted. Likely my fault and just somehow missed it. Getting old.....

 

[loggin]

For reference, I had checked the fluid level the day before and all was good with no leaks to draw it down. Will recheck this weekend again but expecting it to still be fine. I hope to take the problem relief valve out to compare to the spare one I have for the boom once I get time. I will take some pics to share.

Looking forward to see what you find out!!

 

[rScotty]

My guess is that item 80 is the load check and not a relief valve.

I don’t see any work port reliefs in that parts break down

That hydraulic diagram shows two double acting cylinders, one extending while other is retracting so push and pull circuit.

OldnSlow, thanks for your insight, it always helps. I agree that item 80 is a typical load check that we find on most control valves - and that it is not involved in the swing problem we are working on.

Yes, the work port relief valves, aren't shown in that parts break down. For some reason the parts book shows the reliefs on the next page, and we see them again in the attachment to post #18 above.

A couple of things are interesting gleaned from the parts & shop manual:
1. identical relief valves are used for extending and retracting each cylinder. These are only used on the backhoe control valve. There are plenty of other different relief valves on other hydralic circuits on the M59.
2. There are two part numbers for the BH relief valves: Dipper and swing use one # (4 total).
The boom, bucket, and thumb use the other. Like M59owner, I suspect that the difference is the relief setting.

The swing cylinders are double acting and also have their own dedicated swing pump which has yet another primary relief valve in the 3pt case. And interestingly it runs at a sligtly lower pressure than the main. But I don't think either is part of this swing problem.

Air bubble would not cause a relief to fail but a piece of contaminate certainly will especially if that is the style of relief that also has anti-cavitation check built in. The check opens at real low crack pressure to draw oil from tank line to help keep an over running cylinder full of oil. Then if check sticks open it prevents the relief from building pressure.

Right on! That style relief valve does indeed have an anti-cavitation feature. It works by comparing the working pressure vs the "return to tank" pressure....which means that the return to tank pressure is NOT ZERO. It is lower than the working pressure but still significant. Several hundred psi is my guess.

I'm stop here, but will say that anti-cavitation as it is designed in this valve means that sump tank fluid level is important...BUT way more important is to avoid any leaks in the BH hoses&connections - that is absolutely critical.
To a lesser degree of importance, I personally would not let the BH components move around much without the engine running. Use the swing and boom locks. Maybe add a chain on the bucket & dipper.
Any of these could cause temporary BH movement problems just because of air in the system.
My best guess is that debris does about the same thing as air in the relief valve, but not so temporary.
rScotty

 

[m59owner]

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.

As good as new!

 

[m59owner]

Caught a mistake in one of my photos..... I had the pilot pin and spring flipped 180 degrees in error.

 

[loggin]

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.

View attachment 871023

View attachment 871024

View attachment 871019

View attachment 871021
View attachment 871025

View attachment 871026

As good as new!

View attachment 871027

Thanks for the write-up!! Great information!!

 

[rScotty]

Thanks for the write-up!! Great information!!

Yes, a great write-up & nice work. Plus it has been a fun detective story. This thread is going to help everyone with a M59.

I wonder if that M59 style pllot-driven relief valve is also used on other TLBs and the Kubota implement type back hoes?

 

[rScotty]

What is that crud on the pin? Is that why it got stuck?
Or is there just not enough shoulder diameter to keep the spring in place?
Or?

 

[loggin]

Yes, a great write-up & nice work. Plus it has been a fun detective story. This thread is going to help everyone with a M59.

I wonder if that M59 style pllot-driven relief valve is also used on other TLBs and the Kubota implement type back hoes?

Good question. It's been a while since I've had the cover off of the control valve but if memory serves me I don't believe the pressure relief valves are the same design from the outside. Internals might be similar though. I will try to take a photo of the control valve next time I'm up in the shop and post it. Maybe someone else has taken it apart at some point and knows what the internals look like.

 

[Smokeydog]

Thank you for a great diagnosis and write up. Best description I’ve seen to date. I will need to do this too and gain confidence in repair. I guess since my symptoms are temporary, the spring/pin can reseat itself? Maybe an air bubble can cause it unseat? The backhoe is only used about 15-20% of the time in short intervals so there is lots of switching back and forth from3pt mode.

Could the length of spring cause the problem for some and not others? Or how calibrated that spring is? Guessing how to maybe perform a more permanent fix. So far the temporary loss of swing or boom has been a bother. I can sometimes foresee a real problem as I tend to put my M59 in some tight spots.

 

[m59owner]

What is that crud on the pin? Is that why it got stuck?
Or is there just not enough shoulder diameter to keep the spring in place?
Or?


View attachment 871041

Good question. When I took it apart the spring bottom was about a 1/4 below the shoulder. The pin looks discolored in the picture but felt smooth to the touch and once fully assembled moved freely like the one in the new spare. Not sure if there was a surge in pressure that pushed the pilot pin so hard the spring jumped the shoulder or if the spring is wearing out. Time will tell if the same thing happens. if it does, may need to try and source a new spring vs the $650 to replace the entire valve.

 

[spiceman]

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.

 

[jmc]

Credit to OP for properly titling this thread so searchers will be able find it more easily. (Some titles are pretty vague...)