99% its a bad spool valve - need 2nd opinion & suggestions

[grayw0lf1]

Morning!!!

My Kubota L355SS with Kubota 1200 loader has been losing hydraulic power for a long while now. I have to rev it high to get any pressure. I finally started pulling hoses & testing cylinders & the loader valve.
Results: I pulled a hose coming from the 1st position on the 2 spool valve. When actuated, it flows a steady stream out the same hose in BOTH positions, which I believe is BAD!
When I pulled the hose from the 2nd position of the 2 spool valve, it only flows when I move the lever in 1 direction, which I believe is normal.
Am I wrong / missing something?

I don't know the exact specs of the loader valve. I Believe it is about 8gpm, 1/2" In/Out, 3/8" work ports, Open center? I googled the number on the Victor DV 23 FA TS 006 loader valve, but didn't find anything. The loader valve utilizes the tractor's main hydraulic system, not a separate system running off of a 2nd belt driven pump.

2 big questions -
1. I believe the loader valve feeds back to into the hydraulic system at high pressure. It does Not return to tank. The feed/return come from a location between the 3pt lift & the pressure relief valve.
So, do I need anything different for a new valve that does not feed back to the tank, like power beyond? Or am I worrying about nothing?
2. While not needed, would now be the time to upgrade to 3 spool & plug it off until needed? (3pt log splitter, brush grapple, etc).
3. Is there anything else I should be concerned with?

Thanks guys!

 

[Zebrafive]

When you pulled lines, I assume you pulled work port lines, not supply/return. If the spool was for the bucket, you may have regeneration and or float and moved the lever too far?
Have you tried plugging the ports to just that spool's work ports and see if hydraulics improve?
How many TOTAL lines at the valve 7? 6? Seven would have 4 work and P(pressure), T (tank), and PB (power beyond) Six, I am guessing it would be in series with the 3pt hitch. Pressure in an Return to 3pt hitch?
You have open center hydraulics so you need an open center valve. Do not get one rated for a lot more gpm than your tractor supplies, or operation/response will not be as easy to control .

If third function is in your plans, replacement time is the time to get it too.

 

[grayw0lf1]

I did pull the work port lines when testing. No float.
I have not tried plugging the ports.

There are 6 lines total, In, Out, & 2 per cylinder. I believe you are right that the 3pt is in series.

 

[KWentling]

I'm pretty sure what you see is normal for a valve with regeneration. Hopefully someone with more knowledge will chime in.

 

[RickB]

I'm pretty sure what you see is normal for a valve with regeneration. Hopefully someone with more knowledge will chime in.

Agreed. Pressure and flow tests are in order.

 

[wdchyd]

Agreed. Pressure and flow tests are in order.

X2.......pressure/flow test to rule out pump issue

 

[grayw0lf1]

I do have a pressure gauge, but not a flow gauge. The pressure gauge shows it building pressure, though only at higher RPMs.

The reason I suspect the #1 spool on the valve is because spool #1 and spool #2 have differing results. I don't know a lot about regeneration, but I'm not sure that is possible if only 1 line if connected. I could see fluid coming out of the cylinder, but not out of the disconnected hose in either spool position on #1 spool.

Thx for all the input. I'm trying to better understand before I drop the $$$.

 

[PILOON]

I'd suspect the pump is not performing as it should, based on the need for high RPM's needed.

While pressure relief valve is possible but IMO not probable.

Needing high RPM's for decent pressure is a clue of pump defects as well.

One possibility could be air being sucked in via return line as it will compress creating loss of power. Frothy oil would probably be a result and confirm this.

If it were your valve then I believe the loader would drop noticeably and need constant 'burping' to maintain lift.
Another possibility might be the pressure relief valve (often part of the main valve body) but I doubt this from your need for high RPM's.

 

[KWentling]

I do have a pressure gauge, but not a flow gauge. The pressure gauge shows it building pressure, though only at higher RPMs.

The reason I suspect the #1 spool on the valve is because spool #1 and spool #2 have differing results. I don't know a lot about regeneration, but I'm not sure that is possible if only 1 line if connected. I could see fluid coming out of the cylinder, but not out of the disconnected hose in either spool position on #1 spool.



The results are different because the spools are not made the same. A regeneration spool combines flow to help prevent a cylinder from sucking in air when a load moves the cylinder faster than a normal spool can provide flow. I have never experimented with a region valve to atmosphere to know just what to expect, but I'm not surprised at the result you have.
Like others have said, you need to check pressure and flow of the pump. Theres not much to go wrong in a spool valve.

 

[grayw0lf1]

I'd suspect the pump is not performing as it should, based on the need for high RPM's needed.

While pressure relief valve is possible but IMO not probable.

Needing high RPM's for decent pressure is a clue of pump defects as well.

One possibility could be air being sucked in via return line as it will compress creating loss of power. Frothy oil would probably be a result and confirm this.

If it were your valve then I believe the loader would drop noticeably and need constant 'burping' to maintain lift.
Another possibility might be the pressure relief valve (often part of the main valve body) but I doubt this from your need for high RPM's.

You may be right & I may have been chasing a red herring. I just bypassed the loader completely & the pressure is the same, low. I've already taken apart everything on the pressure relief side of the tractor to check for obstructions. The 3pt lift looked fine too. I have not checked the 3pt lift valve itself, so I guess its next. The draft control never has worked. The Shuttle shift works as usual. The shuttle shift should have priority.

I guess its time to keep looking in a different direction.

Thanks guys, I appreciate the help.