Do I have a stuck 3rd function valve. Your assistance requested.

[bitseeker]

My initial idea was that you had got a valve with a motor spool...A and B open to tank in neutral....then I found the Nachi website and the codes for valves...
The code for your valve do not show the "N" for push pin...Push pins are very common, and just use a soft material pin/stick to push with....there is an o-ring on the push pin, that create some friction.....you'll need some 5-10lbs of force...full push stroke should be just little more than 1/4" or so....be careful, if it's a piece of metal, you can damage the spool and the housing....

Try push pin before taking valve apart....

Also I dont know if your Kubota system is a open center with a fixed pump, or a closed center...

If it is an open center, this third function valve must be installed in a power beyond position....

If it is a closed center system, you have the wrong valve too.....

The help here is wonderful. My dealer is 80 miles away, not to responsive, and I suspect, not as expert as you folks.

I did try the push pin and found no change. With no engine off, one side pushes approximately 1/4" and the other approximately 1/8", confirming that there is something blocking the spool I think. The pins pop out with engine on, and neither can be pushed in against the pressure.

I have been trying to understand Power Beyond, and would like a hydraulics book recommendation so that I understand better how the tractor is built so that I can maintain, add, modify, and repair with some knowledge. For instance, I have no idea the difference between "open center" and "closed center" or what a "fixed pump" is. Half the fun of having a tractor is understanding the systems.

As to Power Beyond, the Kubota installation instructions for the 3rd function kit mention PB in the hydraulic changes, and I think PB is Power Beyond. I was confused as to why there are two output lines on the manifold and three others. Now I think those are pressure, return-to-tank, and Power Beyond.

I plan to disassemble and clean the valve. Unfortunately, I do not have the high-pressure fittings to block the hydraulics if I find damage, damage an O-ring, or otherwise cannot re-assemble the valve, so I don't want to render the tractor inoperable while I wait for those parts or a new valve. The dealer seems to stock nothing. If anyone has disassembled one of these Nachi valves, I would appreciate pointers on how and what to watch for.

For other TBNers buying a new tractor with dealer-added options, I suggest requiring the dealer to supply the option's installation instructions the dealer uses in addition to the Operator's Guide and other paperwork. The dealer kept mine, and told me those are not normally delivered to the buyer, but I asked soon enough, and this is the second tractor purchase at that dealer, so he sent what he could find. Before purchase there is lots more leverage. Those instructions are helping me understand the GL5240, and in the case of the defrosted rear and side windows for the cab, made me realize that I bought replacement glass, and should be able to recover the original three panels to keep as spares in case one of the heated ones is broken some snowy March day.

I will post findings and photos when this 3rd function problem is resolved.

-BitSeeker

 

[AKKAMAAN]

The pins pop out with engine on, and neither can be pushed in against the pressure.

That confirms the valve is stuck in transient position, oil pressure will hit both ends of spool and push pins out....

I have been trying to understand Power Beyond, and would like a hydraulics book recommendation so that I understand better how the tractor is built so that I can maintain, add, modify, and repair with some knowledge.

Power Beyond refers to a valve ability to accept full system pressure on the exit port, to make it possible to add an extra valve down stream

For instance, I have no idea the difference between "open center" and "closed center" or what a "fixed pump" is. Half the fun of having a tractor is understanding the systems.

A fixed displacement pump, is a pump that can not change flow other than with the change of rpm...

As to Power Beyond, the Kubota installation instructions for the 3rd function kit mention PB in the hydraulic changes, and I think PB is Power Beyond. I was confused as to why there are two output lines on the manifold and three others. Now I think those are pressure, return-to-tank, and Power Beyond.

You got it right!

I plan to disassemble and clean the valve. Unfortunately, I do not have the high-pressure fittings to block the hydraulics if I find damage, damage an O-ring, or otherwise cannot re-assemble the valve, so I don't want to render the tractor inoperable while I wait for those parts or a new valve. The dealer seems to stock nothing. If anyone has disassembled one of these Nachi valves, I would appreciate pointers on how and what to watch for.

Take the plastic cap off....slide coil off....use wrench on the hex at end of solenoid housing (your "wrench flats")...should be enough to open on one side and pull the spool out....remember what ends comes out first....spool might be non symmetric....

About plugs....if you have old scrap hoses/fittings that fits...use a welder to "plug" one end.....

]

 

[kennyd]

Just remember you CAN NOT "plug" the hoses if you remove the valve! There is the full flow from the hydraulic pump running through those PB (power beyond) lines whenever the tractor is running and you must not block it or bad things can happen.

Here is a good basic resource to read through The Army Hydraulics Manual

 

[bitseeker]

Thanks for the warning. I guess a union to continue the Power Beyond, and caping the Tank and output hoses would work.

Thanks for the manual link. I downloaded it. I see that it does not refer to Power Beyond, and suspect that's a sales term used by equipment manufacturers. I'll do an Amazon search for a hydraulic book.

 

[AKKAMAAN]

This Toro Hydraulic book is covering some good basic s too...good illustrations...

http://www.toro.com/customercare/commercial/education/pdf/09169sl.pdf

This explains the basics of power beyond..

Hydraulic valve power beyond or high pressure carry over

 

[bitseeker]

Thanks AK, both look great. I just bought the Insider Secrets to Hydraulics book and related materials.

 

[countrybumpkin]

I had a third function valve stick after installing on my kubota last year. It worked about three cycles of the grapple and then stuck half open, and three point hitch would not work. I took the valve apart and found a small piece of metal in the valve keeping it from closing. I figure it came from one of the fittings or something during install, just glad it stuck there and not inside the tractor somewhere. You should have no problems with servicing the valve.

 

[bitseeker]

I thought I'd provide an update on the current condition of the GL5240's hydraulic system. The dealer came out twice and was unable to diagnose the problem, so picked up the tractor and took it to their shop. The problems got so bad as they diagnosed it here that backhoe and 3-point function were lost entirely, and the FEL would only lift or drop with symultaneous bucket tip.

They worked on it two full days in their shop, and with Kubota technical service's help, found what they think is the core problem. There was a filter, described by the service manager, as a very fine-mesh screen in the pressure side of the hydraulic system. It had been picking up the manufacturing debris and was almost entirely blocking flow. The tractor has approximately 20 hours on it. Kubota told the dealer that screen should not be there. I'll ask for an exact location of the screen so that other TBNers can check for that screen if they want. They are to return it in a day or two. I can hardly wait!

I am concerned that when I was running the tractor with the 540 RPM flail mower for an hour with the blocked hydraulic system that the rubber seals, hoses, and maybe the oil itself was damaged by getting very hot. I was not aware that it was getting hot when I ran the mower, so don't know how hot it got, but shortly after, I noticed the high temperature. I'd appreciate any opinions on how to determine if there has been damage, and what to do.

TIA

 

[GILLYS CHILLI FARM AUSTRA]

I eas giving consideration to buying an L5740 until i read this post..lol
Sound too tecknical aand complicated to a non mechanic person like me.