L6060 steering binding

[kubotafreak]

Nice find Ruger1980, No one is trying to question your sanity on reading part diagrams. Me, lugbolt, and dgtvrpepair have spent plenty of time looking at what is physically in front of us.
I honestly never looked at the WSM since how dgtvrpepair described made perfect sense to what is visually in front of me on my machine. Given the nature of hose clamps on the cooler I would have never imagined the soft hoses on the driver side, being supplied return flow (to pump, not tank)from the hst housing. If you check the schematic one side is worm clamps the other is wire clamps. This initially lead me to believe the only reason for the hose worm clamps is the pressure drop across the cooler from the pump/steering side.

I still believe air ingress whether through intake or cavitation, is the source of all the problems. Your findings have only complicated the solution to this problem. Mine has a noticeable drop in performance after 2 hours of working the machine. I can tell there is air/cavitation happening in the pump lines at startup (hissing). Machine has less than 50 hours, so I am very interested in fixing this annoyance. Heat in the fluid is the result of my issues, since it takes time for mine to exhibit any symptoms. I can say that on my last l60 series it had several hundred hours and the "worn in pump, steering, hst" seemed to show signs sooner, if not immediately with the steering delay as well has the heat soak hydraulic fluid over time. I am not so concerned with the steering delay myself, as that seems livable, however I cant have the machine loosing power just because of a hydraulic system flaws.

Sounds to me if we go off the prior findings of dgtvrpepair, the hst is returning dirty, "aeriated" fluid back to the system. Which if I'm right, is a little disheartening, because it may not be something we can engineer out of. This might come down to installing clear tubing in the cooler to see the air bubbles.

I have little faith in any dealer level "repair", as we all seem to agree this is a design flaw. I like my dealer, and Kubota products to the fullest. This just seems to be an issue WE must remedy ourselves. If I had not read plenty of others getting pumps, controllers, cylinders, and hoses replaced already I may think otherwise.

 

[kubotafreak]

Ok, I did my own digging. According to the WSM, both parties appear to be right in their own mind. The "return port of the hst casing appears to be a reentrant stack to T fluid. I scoured the diagrams of all systems and can conclude based on the drawings, this is a T tank port. Now Ruger don't shoot me yet. This according to your diagram can theoretically supply flow in the direction of your drawing of the hst circuit in a suction type situation.(pump suction) It may even be how KUBOTA intended.

This is where your thoughts are true dgtvrpepair, you came to the notion the flow demand went backwards, or toward the pump. According to the flow diagrams for the steering system it is counter to the hst diagram. It clearly states the return T from the steering supplies fluid to the hst "return". Either way the fluid flows it is not direct path driven. This factory Y in the loop creates for some issues. Having the cooler in the midst of this competing situation does not provide in my mind for adequate cooling. It also seems to allow air to enter the pump system. I have not obviously had the hst front case apart on one of these to see how the path is milled. I wonder if this reentrant is above fluid levels. If it is then there is the air ingress. Please see diagrams from my L60 WSM. We appear to be in the same boat as before. At least to my feeble mind, I am somewhat glad this hst port is not say bleed off from the hst vdp. Unless someone can prove otherwise, by removing the right side port of the cooler, and blocking off the cooler side to see if forced flow comes out with the machine running. I wont be able to bring my tractor to the shop for a bit, sold my truck in the wait for my new order to come in.

"EDIT"
I pondered this for a bit, and am curious if the T section of the hst is enclosed in a sense, where upon use the tank(cavity) fills up to the point it forces oil out of the return port(not directly connected to the T of the tractor). In other words its fluid level rises and falls based on use. I hope I am making sense, but it would allow for cooling based off HST use, and still be a tank port. This hypothetical situation would flood both steering, and hst returns with fluid upon use. The idea of sharing all the T ports sounds great until you pipe it back up the intake of the pump.

 

[dgtvrpepair]

Im still studying Ruger1980 thoughts on that the line on top of Transmission is a pressure supply line. If makes no sense to me but could be correct. I have never seen a housing that doesn't have air at the top of if it to allow for expansion and shrinking of metals, oil etc. It would have to be completely full of fluid with no air pocket for oil to come out this way back toward the t in the system. It would also seem to me that this would put some pressure back toward the the steering return output to the pump. My only other thoughts are if the transmission line is a supply back to pump would be to then cap off small rubber hose 010 to the t of this system and add a new rubber hose off of steering controller and run it to the back of the tractor to the tank area. Im still afraid that by trying it this way when pump needs demand it might still pull fluid out of controller. I really wish I could talk to someone from Kubota corp. that could help us. There has to be a fix for this. It is amazing how quit the pump is now the way I have it, compared to the way it was before, surging, cavitation. You could hear it bad at lower rpms after it runs for 2 hours and feel it in every hydraulic line on the tractor. I just have to find out if ruger1980 is correct, if so it has to go back to the original way. I can also deal with the small steering bump but losing steering a lot after fluid and tractor get warmed up is not acceptable. I still say it is a design flaw because I now have 250 hours on this machine, I noticed the problem when it was under warranty and had 50 hours on it. From 50-250 it hasn't gotten any worse. This tells me nothing on the machine is failing. I had the steering controller replaced under warranty, I had the steering cylinder rebuilt, all new fluid and filters. I haven't changed the pump because others have and it didn't help. I changed the large suction hose even though it was good. Added better clamps to all hoses that had the cheap clamps. There isn't a leak anywhere.

 

[kubotafreak]

According to the service manual symbolism. HST port 3 is vented below fluid level reentrant. So nothing but the pump suction, or over flooding of tank level will cause fluid motion.

Common hydraulic symbolism

#8 Being the cooler

 

[ruger1980]

During operation the charge pump is constantly pumping oil into the HST case either through leakage in the HST pump/motor or through the charge pressure relief valve. This constant flow of oil quickly purges any air that may be in the HST case if there is any at all upon startup. So the HST case is under a positive pressure and the pump inlets are under a negative pressure. Oil will always flow from positive to negative pressure.

 

[kubotafreak]

Then it sounds like the fluid from the hst case is leaving aerated. Fluid across a relief, or through plate bypass does not bode well for airless fluid. This is probably what I am hearing at idle. The hst case becoming fully saturated and the hst relief venting to the gear case.

 

[ruger1980]

The HST case should have no air inside of it. The case relief valve should only come into play when you have cold oil and the flow through the cooler creates enough pressure to open the relief. Basically it functions as a cooler bypass. During normal operation at operating temps all oil should flow through the cooler. There may be a small orifice to the transmission case but I am not convinced of that as it only shown in one the diagrams and schematics in the WSM.

 

[kubotafreak]

The HST case should have no air inside of it. The case relief valve should only come into play when you have cold oil and the flow through the cooler creates enough pressure to open the relief. Basically it functions as a cooler bypass. During normal operation at operating temps all oil should flow through the cooler. There may be a small orifice to the transmission case but I am not convinced of that as it only shown in one the diagrams and schematics in the WSM.

I have searched this flow diagram, and no where through the 4 stages of operation is the line in question depicted as exceeding normal, or neg pressures. It does not make sense for the charge pump relief to be in any way connected to regulating the low pressure/suction cooler. If it was, it would be shown in the line diagram as a relief. This cooler has soft lines and cannot support anywhere near those pressures.

The only thing I cannot myself confirm is if the tank end of this line is indeed the same as the gear case tank. My guess is it is, and if the right line of the cooler was blocked off, no fluid other than what is in the line would fall from the hst return port while running. If it does then your right, and the diagram is not depicting it correctly as a below tank fluid level vented entry/exit port. I still agree with your original statement that this port is a return(to cooler/pump), so fluid is leaving. However I think it is from negative pressures that drive the fluid movement. If I am incorrect, the drawing should have depicted all the to tank overflow from the pump and hst motor as connected.

 

[dgtvrpepair]

Then it sounds like the fluid from the hst case is leaving aerated. Fluid across a relief, or through plate bypass does not bode well for airless fluid. This is probably what I am hearing at idle. The hst case becoming fully saturated and the hst relief venting to the gear case.

I also have the noise and surging, pulsating in the system from idle up to about 2000 rpm. Now it all makes sense that the hst case has positive pressure and the return line to top of hst case is below oil. I wonder if we added an air removal device that they sell for hydraulics to eliminate air would solve this problem? Now we have to start all over to try and remedy this. Air entrapment is usually caused by a weak pump, old oil, oil getting too hot etc of course the obvious of air sucking in on sustion side. I feel this is not the case with what I have done. Can't be old oil. The pump part number for my l4760hstc is TC050-36440 Same part number for L4060hstc, l6060hstc. The L3560hstc uses a different part number. I have found it very interesting that Titan makes a replacement pump for this and many other kubotas that is 399.00 new on Ebay item 254762884651. I am tempted to try one. That is about what I was quoted to do a flow test of the pump on a dyno that one of the dealers I have talked to has. Im would have already brought it to them but I am afraid they won't run it long enough to see the problem. I am certain I will not buy another Kubota pump for 1000.00 that last 50 hours at most if this is the problem. The only thing else I can think of is another oil cooler or a fan in front of it to keep the oil thicker. Or trying a different hydraulic oil that can withstand more heat. Looks like I have to unblock the return to the top of the pump and deal with the headache again.

 

[kubotafreak]

Your pump is fine... It may be undersized but unless it is scored on the wear plates, its fine. Look at the attached. It appears to be a somewhat self contained region around the two vdp's. It appears to be at the top of the case, so unless the case is absolutely full it will get air. It is not 100% verifiable where this port is fed via the wsm pictures. It does by design look like they attempted to pass the hottest fluid to the cooler like Ruger previously said. Inside the pump/motor cavity, you can see where the casting is open at the right side, by the servo piston, so the surrounding fluid is the same pressure as gear tank T. Which unless the vent candy cane is clogged will be atmosphere.

Seems like its time to field test. I think first we need to verify if pressurized flow is leaving this hst port. Then second we need to verify if the fluid is aerated.(clear hose).

 

[dgtvrpepair]

Your pump is fine... It may be undersized but unless it is scored on the wear plates, its fine. Look at the attached. It appears to be a somewhat self contained region around the two vdp's. It appears to be at the top of the case, so unless the case is absolutely full it will get air. It is not 100% verifiable where this port is fed via the wsm pictures. It does by design look like they attempted to pass the hottest fluid to the cooler like Ruger previously said. Inside the pump/motor cavity, you can see where the casting is open at the right side, by the servo piston, so the surrounding fluid is the same pressure as gear tank T. Which unless the vent candy cane is clogged will be atmosphere.

Seems like its time to field test. I think first we need to verify if pressurized flow is leaving this hst port. Then second we need to verify if the fluid is aerated.(clear hose).

I will try to do some testing this weekend. It is still odd to me that the transmission return line to be pressurized back through the oil cooler to the T to the pump inlet and fighting against steering output flow. Can't understand pressure back to input of pump either. The T I feel like is the problem if the transmission return is pressurized. If it is pressurized I am thinking about taking output of the steering controller off the T, capping it so Transmission output can go through cooler then back to pump and adding a rubber hose from steering controller output to tank rear vented where oil is added leaving a space for air like it has to and see it this resolves the problem. If it fixes it I will get an adaptor to fit the hose and run it to one of the unused plugs on top of the tank in rear and put normal fill plug back. If you get a change to put in clear hose or check for pressure off transmission let us know. Thank all of you for working on this.

 

[ruger1980]

When talking about pressure you must remember that pressure is just a measurement of resistance to flow. There is flow through the HST housing so any resistance will result in a measurable increase in pressure. This pressure is or should be minimal. Most likely below 10PSI, I doubt it should rise above 40PSI. From what I have read the case relief valve value is not published so max case pressure is not clear.

But I seriously doubt the case drain or steering return is the cause of your complaint. The complaint as I have read is mainly lose of steering at a direction change. If this is not accurate please more clearly describe the symptoms. If it in deed during direction change only and is worse at lower rpm's but gets better at higher rpm's, then I would suspect it is related to the flow of the steering pump. More than likely, with numerous complaints it is an inherent characteristic of the system. Whereas during a direction change the majority of the steering pump flow is used to move the servo piston and swash plate from one direction to the other. This sudden demand for fluid may be enough to reduce or eliminate power assisted steering function. This could be aggravated by leakage in the circuit or insufficient flow from the pump.

If you are going to test I would suggest trying operation at 1200, 1800 and max rpm's. I would try this while performing a direction change and attempting to steer at the same time and I would try it with and without loader use at the same time. This would help rule out if there are any issues with pump supply.
I suspect that this is a "normal" characteristic of the system.

 

[dgtvrpepair]

When talking about pressure you must remember that pressure is just a measurement of resistance to flow. There is flow through the HST housing so any resistance will result in a measurable increase in pressure. This pressure is or should be minimal. Most likely below 10PSI, I doubt it should rise above 40PSI. From what I have read the case relief valve value is not published so max case pressure is not clear.

But I seriously doubt the case drain or steering return is the cause of your complaint. The complaint as I have read is mainly lose of steering at a direction change. If this is not accurate please more clearly describe the symptoms. If it in deed during direction change only and is worse at lower rpm's but gets better at higher rpm's, then I would suspect it is related to the flow of the steering pump. More than likely, with numerous complaints it is an inherent characteristic of the system. Whereas during a direction change the majority of the steering pump flow is used to move the servo piston and swash plate from one direction to the other. This sudden demand for fluid may be enough to reduce or eliminate power assisted steering function. This could be aggravated by leakage in the circuit or insufficient flow from the pump.

If you are going to test I would suggest trying operation at 1200, 1800 and max rpm's. I would try this while performing a direction change and attempting to steer at the same time and I would try it with and without loader use at the same time. This would help rule out if there are any issues with pump supply.
I suspect that this is a "normal" characteristic of the system.

I appreciate your help with this. We all have the problem with quick change of direction and momentarily losing steering. We can live with that. The problem is that after the tractor has ran for 2 hours mowing at 540pto, normal speed, temp not above normal, we may lose steering at any moment. It doesn't have enough fluid or pressure to turn fully to left or right. Always worse turning left. You may start turning left and make a complete turn of steering wheel and tires never move. Starts out cold with about 4 turns from full lock right to left. After heats up may take 7 or 8 turns right to left. When gets really bad I can be setting still, noting in bucket of loader, and if try to turn fast can turn steering 10 times in a circle and wheels never move. slow down turning steering slow and move tractor forward slowly and start regaining steering. I have had steering controller replaced under warranty, steering ram tested ok but had hydraulic place change center seal on ram in case it was breaking down under heat. Again all new fluid and filters. I have played with loader while losing steering and it doesn't affect loader operation. But that doesn't rule out the pump because it is a 2 stage pump. If I remember correctly one section of the pump runs the loader and 3 point hitch. The other section runs the pto and steering. Which would make me lean back to a bad pump. It is just hard to believe that all of these pumps are bad at under 50 hours. I also would think I would lose pto when I lose steering if it was the pump.

 

[kubotafreak]

Ruger,
My main complaint is overheating fluid and all the symptoms that follow. I can tell just by listening it is either air being ingested at the implement pump, or relief over run. At idle this would more than likely come from the hst if it is a relief. The times I've used it most is during/after a rain, so the radiator stays clear, mind you this is a very low hour machine. It is my second machine in this class, so we are absolutely talking about a fix of factory design.

Interestingly enough the WSM only answers fluctuation in steering force as air ingestion. If we ponder on the tandem input side of the implement/steering pump, most air will first be noticed and absorbed by the steering pump, thus reagitating this issue. I doubt if any discernible change would be noticed by most when small amounts of air enter the loader valve.


dgtvrpepair,
The tandem pump feeds the regulating valve on the side of the transmission, and internally Y's out to the steering and pto clutch. The pto valve does not demand much flow, other than the pressure to actuate the clutch pack. The steering controller gets most of this flow, and does appear to have a check valve at this place before the steering controller.

Separate issue, your pump has supplied splash lubrication at the pump to engine block interface. My l3560 had this as well. I was surprised to see the l6060 does not. I am going to add this tube from the oil filter housing. Mine has backhoe use, and I have read the pumps gear train can run dry and send shavings into the crankcase.

 

[dgtvrpepair]

Ruger,
My main complaint is overheating fluid and all the symptoms that follow. I can tell just by listening it is either air being ingested at the implement pump, or relief over run. At idle this would more than likely come from the hst if it is a relief. The times I've used it most is during/after a rain, so the radiator stays clear, mind you this is a very low hour machine. It is my second machine in this class, so we are absolutely talking about a fix of factory design.

Interestingly enough the WSM only answers fluctuation in steering force as air ingestion. If we ponder on the tandem input side of the implement/steering pump, most air will first be noticed and absorbed by the steering pump, thus reagitating this issue. I doubt if any discernible change would be noticed by most when small amounts of air enter the loader valve.


dgtvrpepair,
The tandem pump feeds the regulating valve on the side of the transmission, and internally Y's out to the steering and pto clutch. The pto valve does not demand much flow, other than the pressure to actuate the clutch pack. The steering controller gets most of this flow, and does appear to have a check valve at this place before the steering controller.

Separate issue, your pump has supplied splash lubrication at the pump to engine block interface. My l3560 had this as well. I was surprised to see the l6060 does not. I am going to add this tube from the oil filter housing. Mine has backhoe use, and I have read the pumps gear train can run dry and send shavings into the crankcase.

I wonder if Kubota thinks it isn't necessary to have splash lubrication on the L6060 because it has a turbo. All the L60 series above the L4760 all have a turbo. The L4760 and L6060 are pretty much the same engine, just mine doesn't have a turbo and has a different ecm (computer).

 

[dgtvrpepair]

I wonder if Kubota thinks it isn't necessary to have splash lubrication on the L6060 because it has a turbo. All the L60 series above the L4760 all have a turbo. The L4760 and L6060 are pretty much the same engine, just mine doesn't have a turbo and has a different ecm (computer).

I wonder if Kubota thinks it isn't necessary to have splash lubrication on the L6060 because it has a turbo. All the L60 series above the L4760 all have a turbo. The L4760 and L6060 are pretty much the same engine, just mine doesn't have a turbo and has a different ecm (computer).

Not good news. I took the time today to get a 10' 3/8 ID hose to run the return oil outlet of the steering controller to the cap on the tank(oil fill port with vent). I capped off the line that tees to the steering controller return. I put return line back on pump the way it came from factory. With it like this the oil form the transmission return could flow through cooler back too suction of the pump. The unused oil from steering controller runs straight to tank. This cut off too much flow to the loader. The loader was very slow raising and didn't have enough force to raise the front of the tractor when lowered all the way. Their is a lot of oil that comes from the steering controller return. I was able hold the hose and inspect the fluid as it ran back into the tank. At lower rpm that hose really pulsated and fluid coming out is pulsating at the same rhythm that the pump makes noise as we have all heard. At 2000 rpm fluid still pulsates some, but pump makes much less noise. Fluid looks to me like some aeration is in it. So Im lost. I feel like it has the be the pump at this point. Unless somehow the suction filter setup is incorrect. (wrong sized) Any thoughts?

 

[kubotafreak]

Well since your already in the mix, can you place the steering circuit how it is supposed to be. Cap off the Y from the hst return/cooler. Run this cooler return to the gear case tank like how you had tested the PS line. I believe you will find the results to be better. I will be expecting little to no flow from the return, due to the factory WSM diagrams of the steering circuit.

I would like to speculate that during your test you either starved, or introduced air into the pump inlet from the hst return. This would be about the only reason your loader could be affected by what you did. Being a tandem pump, I would bet that it has to get forced flow from the steering return to satisfy the front implement portion.

I think we will find that with little to no flow from the hst housing, it wont overcome the power steering tank line. If my theory holds that means the surrounding region around the hst motor/pump are meant to be flooded by cooled hydraulic steering return fluid. I know this defies the hst diagram, but it would uphold the P/S diagram. It would also make more sense as to being more effective to cool the hst, than to cool the fluid leaving it. The WSM contradicts itself, only one drawing is right...

 

[dgtvrpepair]

Well since your already in the mix, can you place the steering circuit how it is supposed to be. Cap off the Y from the hst return/cooler. Run this cooler return to the gear case tank like how you had tested the PS line. I believe you will find the results to be better. I will be expecting little to no flow from the return, due to the factory WSM diagrams of the steering circuit.

I would like to speculate that during your test you either starved, or introduced air into the pump inlet from the hst return. This would be about the only reason your loader could be affected by what you did. Being a tandem pump, I would bet that it has to get forced flow from the steering return to satisfy the front implement portion.

I think we will find that with little to no flow from the hst housing, it wont overcome the power steering tank line. If my theory holds that means the surrounding region around the hst motor/pump are meant to be flooded by cooled hydraulic steering return fluid. I know this defies the hst diagram, but it would uphold the P/S diagram. It would also make more sense as to being more effective to cool the hst, than to cool the fluid leaving it. The WSM contradicts itself, only one drawing is right...

I will do that tomorrow. I can also find out by doing it this way if the transmission return is pressurized like Ruger says it is. I will be able to watch the flow coming from it the see what it looks like. At least this will separate the 2 returns again. Cooled fluid will be dropped in tank this way. I agree with you that by doing it the other way it was not getting enough fluid form the suction to satisfy the pump 2 halves to run the loader. Could also be why it was surging.

 

[dgtvrpepair]

I will do that tomorrow. I can also find out by doing it this way if the transmission return is pressurized like Ruger says it is. I will be able to watch the flow coming from it the see what it looks like. At least this will separate the 2 returns again. Cooled fluid will be dropped in tank this way. I agree with you that by doing it the other way it was not getting enough fluid form the suction to satisfy the pump 2 halves to run the loader. Could also be why it was surging.

I removed the hydraulic line from the right side of the oil cooler(siting on tractor your right hand is the right side). This is the line that goes to the T, I caped it then connected a 5/8" ID line to the oil cooler then ran that line to rear case breather and fluid fill. This line does have return oil from transmission like Ruger said. It is amazing how much flow. Not what we expected. I would say at least 2-3 times more flow than steering does. About the flow of a water hose not restricted. Steering controller line is 3/8" ID. So I put all of it back like It came from factory. Still had spongy and poor front end loader lift. Had to extend and retract them many times to remove the air. Im thinking that when I ran fluid backward through the system, then reversed it this got air in the loader rams. When loader returned to normal I then caped back off the place that the steering controller goes to the T. Hooked back up a line to the output of the steering controller and ran it back to tank fill. I ran the tractor mowing 2' tall grass for 2 and 1/2 hours today with no loss of steering, I turned it more and faster than normal. I could switch direction form reverse to forward and not lose steering. I'm thinking this may be the fix. It wasn't as hot as I would have liked it to be. About 90. I would like to run it in taller grass when it grows back and in hotter weather to make certain this has got it then I will figure out which plug on top of tank case I can use and run line into it. For test I just have the line though the fill port with a sock secured around it to keep out grass, dirt, etc. and it can still let air out. Loader and lift work like they should. Pump is much quieter, no more surging-pulsating at low RPM. I can barely hear pump running at idle, but just give it a tiny bit of throttle and no noise. Interesting thing is that Kubota makes a kit that basically does the same think for their B2410. Part number 6C150-99600 for los of steering with the same conditions that we have. I even asked Kubota and my dealer about it. They just don't have a problem with the l60 series they tell me.

 

[dgtvrpepair]

I removed the hydraulic line from the right side of the oil cooler(siting on tractor your right hand is the right side). This is the line that goes to the T, I caped it then connected a 5/8" ID line to the oil cooler then ran that line to rear case breather and fluid fill. This line does have return oil from transmission like Ruger said. It is amazing how much flow. Not what we expected. I would say at least 2-3 times more flow than steering does. About the flow of a water hose not restricted. Steering controller line is 3/8" ID. So I put all of it back like It came from factory. Still had spongy and poor front end loader lift. Had to extend and retract them many times to remove the air. Im thinking that when I ran fluid backward through the system, then reversed it this got air in the loader rams. When loader returned to normal I then caped back off the place that the steering controller goes to the T. Hooked back up a line to the output of the steering controller and ran it back to tank fill. I ran the tractor mowing 2' tall grass for 2 and 1/2 hours today with no loss of steering, I turned it more and faster than normal. I could switch direction form reverse to forward and not lose steering. I'm thinking this may be the fix. It wasn't as hot as I would have liked it to be. About 90. I would like to run it in taller grass when it grows back and in hotter weather to make certain this has got it then I will figure out which plug on top of tank case I can use and run line into it. For test I just have the line though the fill port with a sock secured around it to keep out grass, dirt, etc. and it can still let air out. Loader and lift work like they should. Pump is much quieter, no more surging-pulsating at low RPM. I can barely hear pump running at idle, but just give it a tiny bit of throttle and no noise. Interesting thing is that Kubota makes a kit that basically does the same think for their B2410. Part number 6C150-99600 for los of steering with the same conditions that we have. I even asked Kubota and my dealer about it. They just don't have a problem with the l60 series they tell me.

I removed the hydraulic line from the right side of the oil cooler(siting on tractor your right hand is the right side). This is the line that goes to the T, I caped it then connected a 5/8" ID line to the oil cooler then ran that line to rear case breather and fluid fill. This line does have return oil from transmission like Ruger said. It is amazing how much flow. Not what we expected. I would say at least 2-3 times more flow than steering does. About the flow of a water hose not restricted. Steering controller line is 3/8" ID. So I put all of it back like It came from factory. Still had spongy and poor front end loader lift. Had to extend and retract them many times to remove the air. Im thinking that when I ran fluid backward through the system, then reversed it this got air in the loader rams. When loader returned to normal I then caped back off the place that the steering controller goes to the T. Hooked back up a line to the output of the steering controller and ran it back to tank fill. I ran the tractor mowing 2' tall grass for 2 and 1/2 hours today with no loss of steering, I turned it more and faster than normal. I could switch direction form reverse to forward and not lose steering. I'm thinking this may be the fix. It wasn't as hot as I would have liked it to be. About 90. I would like to run it in taller grass when it grows back and in hotter weather to make certain this has got it then I will figure out which plug on top of tank case I can use and run line into it. For test I just have the line though the fill port with a sock secured around it to keep out grass, dirt, etc. and it can still let air out. Loader and lift work like they should. Pump is much quieter, no more surging-pulsating at low RPM. I can barely hear pump running at idle, but just give it a tiny bit of throttle and no noise. Interesting thing is that Kubota makes a kit that basically does the same think for their B2410. Part number 6C150-99600 for los of steering with the same conditions that we have. I even asked Kubota and my dealer about it. They just don't have a problem with the l60 series they tell me.

UPDATE! I have ran the tractor for several hours this way and all seems to be great. I also added a small second steering cooler in line on the return to the tractor case. I also moved the fuel cooler up out of in front of the hydraulic cooler for easier cleaning. The first image is the location that the return oil is going to from the steering controller. The second image is the steering cooler added. The third is the fuel cooler raised up out of the flow of the oil cooler.