Can't find tank return line

[brianrohr13]

Can't find tank return line L4240

I'm moving towards figuring out things so I can self install a valve stack on my Kubota L4240 for all kinds of fun things like a couple remotes and top and tilt. I believe I got the PB lines located but cannot figure out tank return. Since I have a dealer installed backhoe BH-92 I started there. The lines that go to that are BP. Starting at my pump, one goes back through the loader valve and to the backhoe valve (green). Then it goes out of the backhoe and to underneath the operators seat (blue). Pardon my fine art here but can someone help me locate a tank return? And maybe confirm I'm looking at the PB correctly.

 

[brianrohr13]

A couple more thoughts. On the back of the tractor is a QD with a hose plugged in. That is where the BH plugs in. I have to uncouple it and then attach the BH to the hose and QD. In the manual it says do no start up tractor without that hose either connected to the BH or plugged back in to the tractor QD. So I know that it has fluid moving through it anytime the tractor is running and it's important. So it dawned on me that it was PB. This is what got me thinking the green to blue line was just a PB loop. But I just had another thought. Maybe the one coming from the loader valve is PB and it goes into the BH valve. But the one coming out of the BH valve is not PB, that's actually just the return line and it then dumps under the operators seat. Is that how it would work? Could that be how the BH valve work? PB in and then 1 line out to tank? But if that's the way it works, then it begs another question. How is the 3pt hydraulics fed? Maybe that line under the seat is PB and that is the feed on the 3pt. Which would bring me back to trying to find the return line.

 

[Michael In Tennessee]

Yes, you can use your backhoe loop for your valves. I do that on my MX4800. One line is the power beyond output from your loader valve and the second goes to the 3 pt hitch. The output line is power peyond going to the 3rd point, it is not the tank line. At least, that is how it is on my MX4800. However, I don't have the loader valve in the same location. Someplace, you also need a tank line from your new valves. I am unsure on your tractor where that is. Perhaps someone more familiar with your loader valve can help.

Your loader valve should have three lines on it excluding your 4 FEL lines. Power Beyond goes to your backhoe loop. One of the others is Pressure (supply) and one tank. Look on the valve for any markings that indicate function. Many valves are marked.

When you find out which is tank, figure out where it goes. You will have to Tee into that far end for your new valve. Tank can be Teed, other lines cannot.

 

[brianrohr13]

So is there no line going from backhoe to tank? I'm still kinda uneducated in all this but what does the backhoe do for pressure relief if there is no line to return to tank?

 

[Michael In Tennessee]

No, backhoe doesn't use tank. Weird since it is not the last valve in the circuit, but that is how Kubota does it. Tank is not a pressure relief, it's where spent fluid goes from the work ports. Any upstream valve can be used for pressure relief.

For reference, most 3rd function valves also don't use a tank line either.

 

[aczlan]

So is there no line going from backhoe to tank? I'm still kinda uneducated in all this but what does the backhoe do for pressure relief if there is no line to return to tank?

As I understand it, the assumption by the manufacturer is that if you have the backhoe on, you aren't going to be using your rear remotes or your three point hitch.
If there aren't any valves downstream of the backhoe that are turned on, the flow goes straight to the tank.
The reason for the tank line is so that the valve has a unimpeded flow to the tank even if there's a downstream valve that is in use (otherwise you have to build enough back pressure to do whatever work the downstream valve wants done before the fluid can go to the tank).
If you are adding a valve and there is a tank line on your loader control valve, you can tee into that.

Aaron Z

 

[brianrohr13]

Ok. So because the loader valve upstream must have a pressure relief and connection to the tank, the BH won't need one.

And here's a pic of the loader valve. No tank line that I can see. Just the PB (green) running through. Right side to the pump, left side to the BH. And then the four loader lines (yellow).

 

[brianrohr13]

My thought it the tank line is integrated into the back of loader valve I guess. Because I think that's where the tank is. Somewhere back there and under the operators chair.

 

[brianrohr13]

Let me get this straight Aaron. That line from the backhoe that dumps to under the seat is in fact going into the tank. But it's also a pressurized line (pb). So we can't call that a "tank line". So while it's going where I wanna go (tank) it's not the like I'm looking for.

 

[Michael In Tennessee]

Let me get this straight Aaron. That line from the backhoe that dumps to under the seat is in fact going into the tank. But it's also a pressurized line (pb). So we can't call that a "tank line". So while it's going where I wanna go (tank) it's not the like I'm looking for.

That line is input to the 3pt. I believe it internally dumps to tank after the 3 pt. I have no experience on your loader valve, so unless you got a work shop manual or better pics of the valve, I got no idea on tank.

 

[brianrohr13]

That line is input to the 3pt. I believe it internally dumps to tank after the 3 pt. I have no experience on your loader valve, so unless you got a work shop manual or better pics of the valve, I got no idea on tank.

Got it.

 

[ericm979]

The 3pt valve dumps to the tank unless it's engaged to raise the 3pt. That's how my Branson's BH is plumbed in. One hose comes from the loader through two sets of remote valves, into a loop with a set of quick connects and then into the back of the transmission case where the 3pt valve and cylinders are.

You can add your valve in that loop but the valve you add should have no PB (just a plug in that port) and it's tank port must be rated for full system pressure. Many valves do not have that latter feature but there are a lot that do. When you lift something with the 3pt, all the valves in the system see that pressure on their in and PB (or tank if they don't have PB) ports.
You may have to find the manufacturer's spec sheet for the valve you want to see what its tank port can handle as many retailers don't provide that info.

 

[aczlan]

The 3pt valve dumps to the tank unless it's engaged to raise the 3pt. That's how my Branson's BH is plumbed in. One hose comes from the loader through two sets of remote valves, into a loop with a set of quick connects and then into the back of the transmission case where the 3pt valve and cylinders are.

You can add your valve in that loop but the valve you add should have no PB (just a plug in that port) and it's tank port must be rated for full system pressure. Many valves do not have that latter feature but there are a lot that do. When you lift something with the 3pt, all the valves in the system see that pressure on their in and PB (or tank if they don't have PB) ports.
You may have to find the manufacturer's spec sheet for the valve you want to see what its tank port can handle as many retailers don't provide that info.

Exactly.

Aaron Z

 

[Michael In Tennessee]

Exactly.

Aaron Z

I'm not sure. Valves after the valve that is working should not see full pressure.

 

[brianrohr13]

That line is input to the 3pt. I believe it internally dumps to tank after the 3 pt. I have no experience on your loader valve, so unless you got a work shop manual or better pics of the valve, I got no idea on tank.

The is about all I can find for pics. A couple drawings from Kubota website of what I believe is the right valve. The spot that was curious to me in the drawing was the O ring. Wouldn't need O ring just to bolt on a valve to the side of the case. In thinking maybe that's the passage for the fluid to tank? One of the drawing shows where the pressure relief is. As for my pictures. I got a view of under the seat, a side view, and a shot from up underneath.

 

[Michael In Tennessee]

I just looked at the parts diagram @ messick. There is one o-ring on the back side of the valve. That is likely the tank port. Not sure what to do. Some folks have plumbed tank to the fill port.

 

[aczlan]

I'm not sure. Valves after the valve that is working should not see full pressure.

In a power beyond system using valves that have tank ports you are correct.
In the case of this backhoe (which does not have a tank port), if the backhoe is upstream of the rear remotes and one of the remotes is stuck on, the hydraulic fluid leaving the backhoe control valve will have to get to a high enough pressure to either move the load on the rear remote (if something is connected), open the pressure relief for the rear remote valve, or open the pressure relief for the loader valve which is upstream of the backhoe valve.
There is no other way for the fluid to get to the tank.

I just looked at the parts diagram @ messick. There is one o-ring on the back side of the valve. That is likely the tank port. Not sure what to do. Some folks have plumbed tank to the fill port.

If there is an oring under the head of the bolt that is sealing off the port on the valve, there's a good chance that that is intended to be a o ring fitting (ORB).
If you take it out and take it into a competent hydraulic shop they should be able to get you a matching fitting (Tractor Supply or a similar such store in your area may also have the fittings, but it's up to you to make sure that they fit properly).

Aaron Z

 

[brianrohr13]

If there is an oring under the head of the bolt that is sealing off the port on the valve, there's a good chance that that is intended to be a o ring fitting (ORB).
If you take it out and take it into a competent hydraulic shop they should be able to get you a matching fitting (Tractor Supply or a similar such store in your area may also have the fittings, but it's up to you to make sure that they fit properly).

Aaron Z

Check out this picture. This is the o ring (#020) we're talking about. it looks to be between the valve and the tractor (transmission case maybe). But anyways, i think what it means is the there is a hole in the back of the valve (where the o ring is) and it dumps direct into the tank. there's no place to put a fitting there and tie in.

 

[brianrohr13]

I may get to the point of thinking outside the box. Like the fill tube or maybe a drain plug.

 

[aczlan]

Re: Can't find tank return line L4240

Good point, I was looking at the valve backwards.
About the only option I see would be to cut line 110 in this diagram and put in a compression tee:


Aaron Z