Loader Valve / Curl function diagnosis

[GPintheMitten]

I have a Kubota B2620 with the LA364 loader. The boom raises and lowers fine but the bucket curl won't dump.

I switched the quick disconnects to test. When switched the bucket curls but the boom doesn't work. So I switched them back.

I took the loader valve off the tractor, both spools seem to be moving up and down the same amount. I took it to a local hydraulics repair place and this perplexed the guy there. He said it is rare to have the loader valve fail. He connected 2 pressure dials, one to each outlet for the curl and told me to replumb it and check pressure.

After running the boom up and down several times to bleed air, I tried the curl function. Immediately one meter pegged high but as soon as I released the joy stick the pressure bled off. I then moved the joy stick the other way, and there was no pressure on the other curl outlet. This seems to verify that there is an internal fault in the control valve for the curl function.

Does this sound correct? If so, I can buy a new Kubota loader valve for $500. I would like recommendations whether to do that or try and have this one fixed.

If I have this one fixed, there are apparently 2 different versions of this valve and I have to determine accurately which I have before ordering the internal parts. My tractor is serial number 51216. My loader serial number is A3130. But I think it is the tractor serial number that governs the loader valve.

Help please. Thanks.

 

[J_J]

Look at these valves and see if any fits your situation.

Surplus Center

 

[GPintheMitten]

I'm sure there are a couple that I could make work. But I would have to replumb everything. My valve is mounted to the side of the transmission behind the fender with hard lines with banjo fittings for all except a rubber hose for return. I'm not sure the cost savings on the valve would be worth the time effort and costs to replumb.

 

[GPintheMitten]

Does the test with the pressure Guage that I describe prove that it is an internal fault in the control valve?

 

[J_J]

Did you see fluid coming out of both the curl work ports?

You might have a nut off the end of the piston, allowing some pressure in one direction and none in the other direction.

 

[GPintheMitten]

Did you see fluid coming out of both the curl work ports?

You might have a nut off the end of the piston, allowing some pressure in one direction and none in the other direction.

The only thing on both curl ports were gauges. They weren't T'd in.

As to the pistons, a previous test was to switch the quick disconnects between the boom and curl. With them switched, the curl worked but the boom didnt.

So do you think I have sufficiently diagnosed it to the control valve?

JJ I appreciate this help.

 

[J_J]

If you have regen, it might affect your readings.

Try the valve curl lever to the far right which should be power dump.

I would check the pressure by installing the gauge in the IN port of the valve.

 

[GPintheMitten]

I don't know of it have regen or not. How would I determine that?

 

[J_J]

If you have regen, there are two dump modes, fast dump and power dump.

On some valves, the regen is in the first part of lever movement and other valves it is to the far right.

In regen you may not be able to raise the tractor off the ground using the bucket curl, but in power mode you should be able to raise the front wheels off the ground.

 

[LD1]

On my kubota, first position to the right is regen, second is power.

maybe I missed it, but you did not say which direction dont have pressure? dump or curl?

Are you 100% sure you are on the right hoses?

In regen mode, BOTH ports should see pressure. In power mode, only the hose going to the base end of the cylinder will have pressure. In curl, only the rod end hose will have pressure.

What is the PSI range of the gauges? If you are using 0-3000 or 0-5000 gauges, its possible that an empty bucket just dont have enough weight/resistance to notice a pressure reading. Try ditching the hoses and hook the gauges straight to the valve?

Any pictures of how you are testing it now?

 

[J_J]

A regen spool has an extra land cut into the spool to allow the rod end fluid to transfer to the base end of cyl and the spool also blocks the flow to tank.

So no pressure on work port when in regen.

Move the lever further to the right and you should have flow and pressure if connect to a cyl.

When the spool is moved, fluid is going somewhere.

If you have no flow in the power dump, then you do have problems.

There are three places for the fluid to flow internally, through the valve, to the cyl, or through the relief valve.

Purpose of the spool is to shift the flow to certain parts of the valve.

If you have no flow out of the work port and no pressure, then the flow is moving through the valve going downstream.

Curl up should have flow and pressure.

 

[LD1]

So no pressure on work port when in regen.

Pressure on BOTH work ports is what makes regen.

tank is blocked, work ports are connected and applied pressure.

Since both have pressure, and tank is blocked, you only have to make up the amount of fluid the rod occupies. Not the whole diameter of the cylinder. So a 2" cylinder with a 1" rod will move as fast as a 1" cylinder. But also be as weak as a 1" cylinder. Its displacement principal. Thats wh regen wont work in retract.

 

[GPintheMitten]

On my kubota, first position to the right is regen, second is power.

maybe I missed it, but you did not say which direction dont have pressure? dump or curl?

Are you 100% sure you are on the right hoses?

In regen mode, BOTH ports should see pressure. In power mode, only the hose going to the base end of the cylinder will have pressure. In curl, only the rod end hose will have pressure.

What is the PSI range of the gauges? If you are using 0-3000 or 0-5000 gauges, its possible that an empty bucket just dont have enough weight/resistance to notice a pressure reading. Try ditching the hoses and hook the gauges straight to the valve?

Any pictures of how you are testing it now?

Both gauges are attached directly to the curl ports. They are 2000 psi guages. I'm expecting that when I move the joystick the Guage should max out and fluid go through the relief (that is, if the valve was functioning correctly ).

But when i move the joy stick to the left, there is 0 pressure on the Guage for that port.

 

[J_J]

Pushing the lever to the right should be dump slow or fast.

Push lever to left is curl up.

Is your valve in the correct orientation.

 

[GPintheMitten]

Pushing the lever to the right should be dump slow or fast.

Push lever to left is curl up

Right now there are no hoses on the curl ports, just a Guage on each one.

When engauged, one reads 0 pressure, so doesn't that prove that I need a new loader control valve?

 

[J_J]

Not in the case where he has gauges in the ports, because there is no flow.

I have already ask him to see if there is fluid flow at full lever. No answer yet.

The gauge should be in the valve IN port, and cyl connected..

The only thing he is doing is to make the fluid flow over the relief valve.

 

[GPintheMitten]

Not in the case where he has gauges in the ports, because there is no flow.

I have already ask him to see if there is fluid flow at full lever. No answer yet.

The gauge should be in the valve IN port, and cyl connected..

I didn't want to dump oil on the ground.

I'll go out in a few minutes and take the guages off and see where there is flow.

 

[J_J]

Put the hoses in a bucket and work both levers to the max for a few seconds.

 

[GPintheMitten]

There are hard lines at each.port with banjo fittings. I can't put a Guage in series and still have flow without some major plumbing.

 

[GPintheMitten]

Put the hoses in a bucket and work both levers to the max for a few seconds.

Ok. I'll try that and report back.