I'm troubleshooting the hydraulics on my tractor right now. I thought I had correctly identified the sluggish loader and power steering as a weak pump, but today I discovered something very strange. If I'm running the loader and I turn the wheel in the right hand direction, the loader goes a whole lot faster all of a sudden (about what I would expect as normal speed for this machine. Also, the power steering works great, again in the right hand direction only, but only if the loader is operating. If I turn left, I get no response from the power steering (as usual), and the loader runs slowly as normal, and if I turn right when the loader is not operating, I get no power steering. Now I'm leaning towards something in the proportioning valve being the problem right now, but I have no idea where to start as far as troubleshooting this issue. I did just look over the plumbing from the loader's spool valve to the proportioning valve and all of those hoses are connected properly, so we can rule that out. I'm curious to know, has anyone else had this kind of behavior from one of these tractors, and if so what was the issue? Thanks in advance.
Kioti LB2204 with KL122 Loader Proportioning Valve Issue
- Thread starter RandR10
- Start date
Okay, so I've done a bit of research on what a priority valve does. I found this video that gives a good explanation of when they're needed.
From what I'm gathering here, I think the steering on this machine is likely a closed center system, which I think means that no oil passes through during idle like the loader spool valve will do. Oil just deadheads into that valve, so you need to have this priority valve to allow it to have constant pressure while the overflow pressure doesn't stall the pump.
That overflow goes to feed the loader. I'm actually not sure what the selector valve is there to do other than maybe just turn the loader hydraulics on and off.
This leads me to believe that the problem is in the steering itself.
I'm not sure how it works exactly, but when you turn the wheel, the pitman arm pushes the drag link into this cylinder, which causes a sleeve to slide along this cylinder, then actuates a valve internally that will then assist in the direction that you're pushing. My guess here is that the left turn function is broken in such a way that the oil just passes through instead of putting pressure into the cylinder. It would follow that it has also failed in such a way that the oil passes through when the steering is in neutral position as well. This would explain why the loader doesn't get any oil unless you're turning right and the steering system is able to deadhead again like it should always do, building pressure past the priority valve and pumping into the overflow circuit. The only thing this doesn't explain though is why the steering doesn't work at all when the loader isn't pressurized too. It's almost like the priority valve is working in reverse there too. Either way, I think I have a decent starting point to start tearing things apart and looking for problems, starting with this steering unit.
If anyone who has experience with these systems can tell me whether I'm sound in my thinking on this, it would be much appreciated. I don't have a ton of experience with hydraulics, so I'm sure I'm making some errors here. I am finding it impossible to find info on how these particular priority valves work internally, so this kind of guesswork is all I've got to go on until I can get it apart.
From what I'm gathering here, I think the steering on this machine is likely a closed center system, which I think means that no oil passes through during idle like the loader spool valve will do. Oil just deadheads into that valve, so you need to have this priority valve to allow it to have constant pressure while the overflow pressure doesn't stall the pump.
That overflow goes to feed the loader. I'm actually not sure what the selector valve is there to do other than maybe just turn the loader hydraulics on and off.
This leads me to believe that the problem is in the steering itself.
I'm not sure how it works exactly, but when you turn the wheel, the pitman arm pushes the drag link into this cylinder, which causes a sleeve to slide along this cylinder, then actuates a valve internally that will then assist in the direction that you're pushing. My guess here is that the left turn function is broken in such a way that the oil just passes through instead of putting pressure into the cylinder. It would follow that it has also failed in such a way that the oil passes through when the steering is in neutral position as well. This would explain why the loader doesn't get any oil unless you're turning right and the steering system is able to deadhead again like it should always do, building pressure past the priority valve and pumping into the overflow circuit. The only thing this doesn't explain though is why the steering doesn't work at all when the loader isn't pressurized too. It's almost like the priority valve is working in reverse there too. Either way, I think I have a decent starting point to start tearing things apart and looking for problems, starting with this steering unit.
If anyone who has experience with these systems can tell me whether I'm sound in my thinking on this, it would be much appreciated. I don't have a ton of experience with hydraulics, so I'm sure I'm making some errors here. I am finding it impossible to find info on how these particular priority valves work internally, so this kind of guesswork is all I've got to go on until I can get it apart.
Dave M7040
Elite Member
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- Dec 10, 2012
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- Williamstown Ontario Canada
- Tractor
- Kubota M7040 Nuffield 465
Your system has errors in hose and pipe connections to act like it does. The power steering would be open center.
There could be a priority flow control valve whose job it is to ensure that the power steering always has the flow and pressure it needs...
Dave M7040
There could be a priority flow control valve whose job it is to ensure that the power steering always has the flow and pressure it needs...
Dave M7040
Another update. The priority valve in this application works nothing like the one in the above video as far as I can tell.
This valve sits on the top of the priority valve block and partitions oil between the steering and loader. I believe the hole in the center allows oil to pass through at all times no matter the position of the valve. The loader only gets oil when the plunger moves up in its bore. I was able to verify this by hitting it with compressed air. There's always flow coming out the top. At 110 PSI, the compressed air was not enough to make the spring move up, so nothing ever came out of the loader ports.
This is the only other spring loaded valve in the block, and it looks like it's just a simple spring loaded over pressure valve. At some pressure level, it would allow oil to pass from the inlet to the outlet of the block if the pressure gets too high.
Both valves seemed to be functioning properly and there was no obvious problem with either as far as I could see. Also, the valve on the block that you dial with your hand, I looked down the bore and could see that this is basically the same as a ball valve. Turn it 90 degrees it's full open, turn it back, it's full closed. This allows oil to completely bypass the loader and power steering circuits and direct more flow straight to the 3-point hitch hydraulics.
No pictures on this one, but I pulled the power steering cylinder off and gave it a quick look. Just having it off the machine and pushing the cylinder with only air in it back and forth, I found that the valving seems to be doing its job. In either direction, the cylinder didn't want to move unless I actuated the spring loaded sleeve internal to the valve in the appropriate direction. I found what looks like transmission fluid coming out of the cylinder, which is completely different than what's in the rest of the hydraulics, so it doesn't look like oil was actually making its way into it. I'm thinking based on my findings here that the hoses may have just been on backwards. I don't know why that would make it work only in one direction, but I'm going to make 100% sure it's correct when it goes back together. It's late so I'm not going to try it tonight. I'll probably throw it back together sometime tomorrow and report back.
This valve sits on the top of the priority valve block and partitions oil between the steering and loader. I believe the hole in the center allows oil to pass through at all times no matter the position of the valve. The loader only gets oil when the plunger moves up in its bore. I was able to verify this by hitting it with compressed air. There's always flow coming out the top. At 110 PSI, the compressed air was not enough to make the spring move up, so nothing ever came out of the loader ports.
This is the only other spring loaded valve in the block, and it looks like it's just a simple spring loaded over pressure valve. At some pressure level, it would allow oil to pass from the inlet to the outlet of the block if the pressure gets too high.
Both valves seemed to be functioning properly and there was no obvious problem with either as far as I could see. Also, the valve on the block that you dial with your hand, I looked down the bore and could see that this is basically the same as a ball valve. Turn it 90 degrees it's full open, turn it back, it's full closed. This allows oil to completely bypass the loader and power steering circuits and direct more flow straight to the 3-point hitch hydraulics.
No pictures on this one, but I pulled the power steering cylinder off and gave it a quick look. Just having it off the machine and pushing the cylinder with only air in it back and forth, I found that the valving seems to be doing its job. In either direction, the cylinder didn't want to move unless I actuated the spring loaded sleeve internal to the valve in the appropriate direction. I found what looks like transmission fluid coming out of the cylinder, which is completely different than what's in the rest of the hydraulics, so it doesn't look like oil was actually making its way into it. I'm thinking based on my findings here that the hoses may have just been on backwards. I don't know why that would make it work only in one direction, but I'm going to make 100% sure it's correct when it goes back together. It's late so I'm not going to try it tonight. I'll probably throw it back together sometime tomorrow and report back.
So more update on this. Instead of just throwing the steering back together this morning I decided to test everything with the sleeve installed on the end of the cylinder using compressed air. It's a good thing I did because I found that the left turn actuation was not occurring. There's some wear internal to the valve inside the steering so there's slop in it. This makes it so the shoulder bolt that runs the sleeve up and down the shaft here runs into the end of its slot before it can open the valve in that direction. I was unable to figure out how to disassemble this valve to try and do a repair, so I had two options left. 1: I could lengthen the slot. 2: I could narrow the shoulder on the bolt just where it rides in the slot so it can run the valve further before it hits the end of the slot. I opted for Option 2.
Thankfully the area on this bolt where it was colliding with the end of the slot was already wallowed out a bit, giving me a nice reference point to use when narrowing. I chucked this up into the lathe and took off about a 1/16" off both spots. Putting this all together yielded good results, at least for the one way steering issue. Steering works in both directions now. Partial success!
Unfortunately I still have the problem of not being able to get pressure to either the loader or the steering unless both are being actuated simultaneously.
This leads me to believe that the above spring-loaded valve is the problem. This is the same one I showed in the first pic in Post #4 above. I even think there may be parts missing inside the valve block, because I cannot see how this thing should allow pressure to build in that chamber the way it sits. Everything is just going to blow through that hole. That hole in the bottom of the valve looks like it should seat on a needle or ball something in order for it to actually function in any meaningful way. That said, I'd like to put the feelers out. Does anyone know where I can find a parts breakdown or schematic of the inside of this valve block? Even if someone could pull their still-functioning one apart and tell me what's inside would be fine. Neither the KL122 manual nor the LB2204 shop manual show this. They just show the outside of the block with the labels for where the loader hoses should hook. I know this has to be the problem because it's the only logical point of failure that would cause this symptom. The other valve in the lower left hand side of the block is obviously functioning fine because it is just an overpressure valve, and I'm still able to get pressure in that chamber if both circuits are under load.
Thankfully the area on this bolt where it was colliding with the end of the slot was already wallowed out a bit, giving me a nice reference point to use when narrowing. I chucked this up into the lathe and took off about a 1/16" off both spots. Putting this all together yielded good results, at least for the one way steering issue. Steering works in both directions now. Partial success!
Unfortunately I still have the problem of not being able to get pressure to either the loader or the steering unless both are being actuated simultaneously.
This leads me to believe that the above spring-loaded valve is the problem. This is the same one I showed in the first pic in Post #4 above. I even think there may be parts missing inside the valve block, because I cannot see how this thing should allow pressure to build in that chamber the way it sits. Everything is just going to blow through that hole. That hole in the bottom of the valve looks like it should seat on a needle or ball something in order for it to actually function in any meaningful way. That said, I'd like to put the feelers out. Does anyone know where I can find a parts breakdown or schematic of the inside of this valve block? Even if someone could pull their still-functioning one apart and tell me what's inside would be fine. Neither the KL122 manual nor the LB2204 shop manual show this. They just show the outside of the block with the labels for where the loader hoses should hook. I know this has to be the problem because it's the only logical point of failure that would cause this symptom. The other valve in the lower left hand side of the block is obviously functioning fine because it is just an overpressure valve, and I'm still able to get pressure in that chamber if both circuits are under load.
Okay, so I finally made some headway on this. In the parts manual this whole valve block is called the Hydraulic Block Group/Oil Pressure Relief Assembly. I didn't recognize it before because they have it displayed from the back side of the unit for some reason, and I hadn't seen it from that angle until I had it off the machine and dismantled it. The part in question here that I think might be the problem is the Flow Divider Assembly (the piece I have in my hand in the above photo). I haven't been able to make heads or tails of whether it's malfunctioning. As I said earlier, I didn't figure out a way to disassemble it, although they do show the two ported sections there as separate pieces in the parts breakdown. At any rate, this thing moves up and down if you push the spool back and forth manually, so I'm not sure there's an issue.
Now that I have a part number to search, I found that they used this same Flow Divider in several of the B and M-series Kubota tractors. Many of those tractors apparently had this same problem as well. On one of the threads I read, one of the commenters claiming to be a former Kubota mechanic said "There was a bulletin on this problem and a kit to repair it a few years ago. I don't work at a dealership anymore so I don't have access to the bulletin. what they did though was separate the steering return and return it directly to the transmission instead of the hydraulic pump suction line. It shouldn't be very hard to come up with the fittings to do it yourself." I'm probably going to try this next. Can anyone here speak to whether this is sound advice?
Now that I have a part number to search, I found that they used this same Flow Divider in several of the B and M-series Kubota tractors. Many of those tractors apparently had this same problem as well. On one of the threads I read, one of the commenters claiming to be a former Kubota mechanic said "There was a bulletin on this problem and a kit to repair it a few years ago. I don't work at a dealership anymore so I don't have access to the bulletin. what they did though was separate the steering return and return it directly to the transmission instead of the hydraulic pump suction line. It shouldn't be very hard to come up with the fittings to do it yourself." I'm probably going to try this next. Can anyone here speak to whether this is sound advice?
Harry in Ky
Veteran Member
Sounds like an excellent plan to me. The hydraulic pump suction line on anything should have the fewest possible points for air ingestion as possible.
You've got me thinking this may not be my issue now. I missed in his post that he said it dumped into the suction line. On mine it doesn't actually return to the suction line, it dumps back into the hydraulic block and shares a gallery with the "out" port hose on the loader valve which then directs the fluid through a hard line that goes into the top of the transmission cover. Maybe he misspoke when he said that or possibly I just have a different configuration. The hydraulic block assembly looks different on those tractors even though they use the same Flow Diverter valve, so maybe I just have a different setup. I may still try this just to see what happens because it's the exact same behavior mentioned in that thread. I just need to get the appropriate sized plug and then I'll dump the power steering into the fill port on the transmission just to test. If that fixes it I can properly plumb the discharge hose to the side of the transmission case.
Dave M7040
Elite Member
- Joined
- Dec 10, 2012
- Messages
- 2,747
- Location
- Williamstown Ontario Canada
- Tractor
- Kubota M7040 Nuffield 465
The individual who made reference to the service bulletin and dumping directly into the transmission instead of the pump return is someone whose advice should be regarded as being much more knowledgeable than most on the forum. When I have a problem I cannot solve I turn to him for advice.
Dave M
Dave M
Harry in Ky
Veteran Member
And so who is "him" that's so knowledgeable?