Interesting.
Can you provide details of what is necessary to make the modification?
SDT
L6060 steering binding
- Thread starter BUZZJ
- Start date
Can you provide details of what is necessary to make the modification?
SDT
The best I can explain it is that the steel return line that goes to the top back of pump needs blocked off. There are 2 bolts that hold it to the top of the pump. Under the rectangle piece that the bolts go through is a round gasket. I put a thin flat piece of metal bigger than the opening under the round gasket and top rectangle piece then added a second gasket between the new piece of metal and the pump. Then snugged it all down. Don't over tighten the 2 bolts so you don't warp the top rectangle piece. Their is not pressure on this line just return. Check for leaks. This stops return fluid from going back into suction of pump and makes it all go through cooler then to tank return. I tried to upload an image of the diagram from Messick's and it won't let me. Any questions you can call me at 501-354-5085 8-5 central time Monday-Friday ask for Danny.
Danny, any chance you made contact with Kubota with your solution? As you may remember, even the rep was bumfuzzled with this deal and he-and the engineer he was working with-had no clue which direction to go. And of course, the dealer wasn't much help either because of that.
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
Not that I know the specs on the pump at all, but I cant help but wonder if that factory bypass is more for pump anti cavitation. It is more than likely sacrificial to give up power steering flow. That pump in the factory configuration would be given low resistance (filter) suction, along with the low pressure T return flow. This combination would almost certainly give a total pressure of nominal-to positive on the input side of the pump. I don't doubt you made the steering 100 times better, but at what cost.
I am familiar with this tractor, and I have worked on it in the past, along with Kubota reps and another tech at the store I worked at, at the time.
Given the store's willingness (or unwillingness) to source the tooling, we could not properly do a flow test. I suspected either a suction side leak, or perhaps a weak main hydraulic pump but without a flow test that could not be properly eliminated. The pressures were all within spec but pressure alone doesn't tell the whole story. I felt that the pressure at low engine speed was a little lower than I liked to see but Kubota's testing procedure specifies to test at rated engine speed-e.g., 2500 RPM give or take on his tractor. I found a small suction side leak at the cooler an addressed that, which I thought solved it. Apparently not. I left the dealer before any other solutions could be looked at.
No I did not contact Kubota. They would never let me talk to anyone higher up when I called.
I get what you are saying. By doing it this way I can see that the pump has to supply the extra fluid that was before returning from steering to the pump. And it has to increase the amount of oil returning through the cooler back to the tank by the same amount that was returning to pump. All I know is that before steering bump when turning especially if changing direction is all gone. Also before the pump surged and cavitated at many rpms. Had air in the steering all the time after running and mowing a few hours. Now pump is quite at all rpm and no air in steering. Worst thing I could see happen is that over time pump could possible fail sooner. I my opinion without cavitation, surging, and air in the system the pump should last longer and the hydraulic oil is cooler throughout the entire system. Only time will tell. If I have to I will purchase a new pump.
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
I am very interested in your solution. It absolutely seems logical to me how your describing. I have had a few grand l's, and just lived with the inconvenience. I just wonder where the air ingress is coming from. (seal from steering controller, cooler, hose) Did you have any area in the steering hydraulic routing that was oil filmed, or dripping?
No oil film, no leaks, I personally changed the large suction hose even though it wasn't leaking and added better clamps to the other rubber hoses on the oil cooler and steering controller to check for air getting sucked in. I had Kubota change the steering controller-no change. I removed the steering ram and had it tested at a shop that rebuilds rams(cylinders) and they went ahead and replaced seals in case it was failing heat related. Still the same. Doing the bypass took care of it. What is happening is that when the extra demand for steering along with changing direction, the oil is getting pulled from the steering controller back through the return that normally goes to the top of the tank. The top of the tank is an open area that is vented through the fill port at the back of the tractor. So it is suppose to have air on top of the oil. This is where the system can self bleed out air. Problem is that when it is pulled backward to supply demand it is pulling in the air on top of the tank and mixing it with the oil a little every time it hits the steering bump(changing direction) until it just keeps getting worse the longer the tractor is ran. Then after it sits the steering ram will self bleed out the air by turning steering. I don't understand how they keep selling all these tractors with this problem and all the dealers say they have never heard of it. Kubota tells me they have never had this problem with any of the grand L60 series. Mine is a 2015 that started this under warranty with about 60 hours, went to shop many times, never got resolved. Probably had the problem from the beginning I just didn't notice it because of being extremely easy on a brand new machine.
kubotafreak
Well-known member
Equipment
GRAND l6060, L3560, B6100, gr2100, tg 1860, g1800, g1900, g2160
You have me curious as to the idea of a flow check valve on the cooler return pipe>T. On the diagram this would be line #80 or the soft tube leading out of the cooler. This would prevent the air ingestion, but only testing would confirm if this would be enough to mitigate the lack of assist in the steering. Another issue could be the suction generated by the pump being too much, causing strain of the soft cooler lines, or check valve.
This seems to be directly proportional to the hydraulic suction filter. The more it gets clogged, the more the demand is met by steering return flow. I know you have figured out a way to do eliminate the link between the pump and steering return flow. I am just trying to see if there is another way to satisfy the flaw in their design. It does make sense to me why they would want to add steering T flow to the pump. As you pointed out already air ingress would be the first major issue... Once I find a power steering check valve with double barbs the right size Ill try this out and report back.
This seems to be directly proportional to the hydraulic suction filter. The more it gets clogged, the more the demand is met by steering return flow. I know you have figured out a way to do eliminate the link between the pump and steering return flow. I am just trying to see if there is another way to satisfy the flaw in their design. It does make sense to me why they would want to add steering T flow to the pump. As you pointed out already air ingress would be the first major issue... Once I find a power steering check valve with double barbs the right size Ill try this out and report back.
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I like you way of thinking. It is going to take someone like you and I to get this fixed. I thought really hard about a one way check valve. I think when studying it that this would stop air from coming form line 80 tank return but when demand ask for extra fluid the steering would still bump momentarily due to stopping oil flow when pump pulls for extra oil from return line 40 to pump. This would eliminate air in the system so would be an improvement. It could possibly work because it would be harder to pull oil back this way. If you try it and I am wrong please let us know. That would be a better fix if it works. I can't see how the design flaw is that the suction filter isn't allowing enough oil for pump. I have even changed all hydraulic filters including suction along with super udtII fluid and it still had the same flaw.
The more I study the flow of this system I am also going to get a one way check valve and try it in the return of the rubber hose off the cooler like kubotafreak suggest. If it tries to pull from return this will stop it and if it pull from input to pump it will always have oil there, so it can't get air this way.
You have the flow of this circuit backwards. The oil flows from the top of the HST case (case drain) through the cooler and joining with return oil from the steering valve and then to the inlet of the hydraulic/steering pump. Please see the diagram below.
What @dgtvrpepair has done is reverse this flow and doing so the hottest oil in the system is now not being cooled by the cooler. The oil now has to return to the transmission sump through the case relief valve.
The symptoms that you are experiencing are more likely due to the loss of oil flow to the steering valve due oil being prioritized to the HST servo when changing directions. This can be aggravated by weak pump or plugged filter
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The diagram you have on here isn't for the grand l60 series. The hose routing that kubotafreak has listed earlier in this discussion is correct. I have the service manuals for the L60 series and this is the diagram for our tractor. I am not reversing fluid flow.
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Using the diagram you posted I have drawn up the correct flow for that circuit. By blocking the steering valve return (blue/orange line) to the inlet line (green) you are diverting oil through the cooler in the opposite direction intended and out through the case relief shown in the yellow circle.
By looking at the diagram I have posted I can see where it is confusing. Our service manual is wrong. The lines are not laid out on the tractor as the diagram shows. They are laid out like the images kubotafreak posted. These are not in our manual but can be seen on Messick's if you log in with an email. By blocking fluid at return to pump line 040 at pump just stops some of the return oil to the pump. The main return is line 080 that goes through cooler then to transmission return. This is the tank storage of fluid. It does not go through any relief valves just normal return to tank. I have been all over the tractor and followed all the lines that have to deal with steering and return oil. Get under front of tractor with hood up and follow them.
I can explain it to you, but I cannot make you understand apparently. But I will try one more time.
Below are 2 images showing the structure of the HST and the hyd flow shown above. In the HST structure image it shows reference number 3 as the "Outlet port (to the oil cooler)". This would indicate that oil flows out of the HST housing to the oil cooler not into the HST housing. Also the HST housing is a separate sealed compartment and is only connected to the transmission housing/sump via the case relief valve and the suction port to the charge pump inlet port. The hydraulic pumps draw their oil supply from the transmission sump not the HST housing.
The next image is the flow diagram attached above but marked up to show the 2 lines from the cooler, reference number 17. Item 080 in parts diagram is colored yellow and Item 040 in the parts diagram is colored blue. The arrows next to these depicted lines clearly show the direction of oil flow in the circuit.
By blocking line 040 at the hyd. pump you have essentially created this flow path.
Below are 2 images showing the structure of the HST and the hyd flow shown above. In the HST structure image it shows reference number 3 as the "Outlet port (to the oil cooler)". This would indicate that oil flows out of the HST housing to the oil cooler not into the HST housing. Also the HST housing is a separate sealed compartment and is only connected to the transmission housing/sump via the case relief valve and the suction port to the charge pump inlet port. The hydraulic pumps draw their oil supply from the transmission sump not the HST housing.
The next image is the flow diagram attached above but marked up to show the 2 lines from the cooler, reference number 17. Item 080 in parts diagram is colored yellow and Item 040 in the parts diagram is colored blue. The arrows next to these depicted lines clearly show the direction of oil flow in the circuit.
By blocking line 040 at the hyd. pump you have essentially created this flow path.
I guess what has me thrown off is that line 080 says oil return on messick's images. So from what you are saying is that the pump on all of these is weak at 50 hours? Like I said before all filters are new including suction, and new super udt hydraulic oil. Or do you think we all have to live with close to 50k tractors losing steering when changing direction and losing steer all the time after running mower on rear pto for 2 hours or more because pump on this unit isn't large enough? Any suggestions on how to fix this properly?