Case Drain – KX41-2V

[xenophon.nl]

I'm looking to rent a hydraulic flail mower for my Kubota KX41-2V and I've run into a bit of a snag with the hydraulic setup. The mower I'm interested in requires a case drain, but I’m having trouble locating where this should be connected on my excavator.

Here’s the situation:

• I’ve been told that there should be a valve somewhere to convert one of the hydraulic aux line to a case drain. However, despite searching, I haven’t been able to find anything that looks like it could be a case drain connection.
• I need to figure out if there’s an existing connection I’m missing or if I’ll need to add one.

Questions:

1. Should there be a case drain connection on my Kubota KX41-2V? If so, where exactly should I be looking?
2. If I can’t find a case drain connection, how can I add one? Are there any specific parts or modifications needed to make this work?

Any advice or guidance would be greatly appreciated. Thanks in advance for your help!

I also included some pictures and diagrams.

 

[TheOldHokie]

I csnt abswer as to what is on your machine but the operators manusl should.

Functionally a case drain is simply a hose connection from the implement that goes straight to tank on the machine - aka third line. It should present as little back pressure as possible to the implement.

You can rig one yourself by adding a coupler that goes straight to tank on your excavator.

Here is a fancy OEM third line outlet manifold on a Case skid steer. The two larger lines are the normal A and B bidirectional pressure connections to the control valve. The smaller middle third line is one way into the skidsteer and does not go to the valve. It goes straight to tank.

Dan

 

[GreensvilleJay]

hmm, maybe look at the hydraulic 'drive' motors ? If they have a small 3rd hose, that'd be a 'drain' line, follow it back to the tank ??
The WSM is 'somewhere on the net' as I grabbed a copy years ago.
The challenge will be physically plumbing it. Aint a whole lotta room in the beaties for 'upgrades' !

 

[xenophon.nl]

Included is the hydraulic diagram in case of anyone is able to read that and determine if there should be a valve to activate the case drain.

 

[GreensvilleJay]

the dotted line from tank...left...up...to motors is the 'drain'. You could/would Tee into that...IF you can access it !

 

[Henro]

Included is the hydraulic diagram in case of anyone is able to read that and determine if there should be a valve to activate the case drain.

LOL… That highlighting looked familiar! I must’ve posted that image somewhere because I looked at my file for the KX-41-2V workshop manual and the highlighting is the same as I have here!

I don’t have an answer to your question. But I can say, and I think TheOldHokie would agree, that the return to tank is generally , and may be always, an unrestricted line that goes back to the tank. So if you need a return to tank route, you need to find either a line serving that purpose or you need to feed your return back to the tank somehow on your own.

 

[TheOldHokie]

LOL… That highlighting looked familiar! I must’ve posted that image somewhere because I looked at my file for the KX-41-2V workshop manual and the highlighting is the same as I have here!

I don’t have an answer to your question. But I can say, and I think TheOldHokie would agree, that the return to tank is generally , and may be always, an unrestricted line that goes back to the tank. So if you need a return to tank route, you need to find either a line serving that purpose or you need to feed your return back to the tank somehow on your own.

Yes.

Another attribute of case drains is that they should terminate below the fluid level in the reservoir.

In a pinch that could be as simple as removing the tank fill csp and sticking a hose in the tank with the end below fluid level.

Installung a tee in a valve or motor return line is frowned on.

Dan

 

[Henro]

Yes.

Another attribute of case drains is that they should terminate below the fluid level in the reservoir.

In a pinch that could be as simple as removing the tank fill csp and sticking a hose in the tank with the end below fluid level.

Installung a tee in a valve or motor return line is frowned on.

Dan

I never heard the term case drain before. Is there a reason for that term? I’ve always just heard return to tank line or something like that.

In other words, was there a point in time when some kind of hydraulic case was drained back to the tank? Just an intellectual curiosity question. An answer is likely of no use in the real world today.

 

[TheOldHokie]

I never heard the term case drain before. Is there a reason for that term? I’ve always just heard return to tank line or something like that.

In other words, was there a point in time when some kind of hydraulic case was drained back to the tank? Just an intellectual curiosity question. An answer is likely of no use in the real world today.

Its called a case drain because that is what it does. Hydraulic motors and pumps all bypass oil internally and that bypass oil gets forced into the case area outside of the pumping chamber. The result is the case gets pressurized and damages the pump/motor. Shaftvseals are psrticularly vulnerable. The cure is to plumb a dedicated drain line between the case on the pump/motor and the reservoir on the machine. That bleeds off the pressure and protects the pump/motor.

Dan

 

[Henro]

Its called a case drain because that is what it does. Hydraulic motors and pumps all bypass oil internally and that bypass oil gets forced into the case area outside of the pumping chamber. The result is the case gets pressurized and damages the pump/motor. Shaftvseals are psrticularly vulnerable. The cure is to plumb a dedicated drain line between the case on the pump/motor and the reservoir on the machine. That bleeds off the pressure and protects the pump/motor.

Dan

Thanks Dan. So the case drain is then a separate path back to the tank, as compared to whatever line might be used for fluid exiting a cylinder? Or is it just semantics?

Not trying to be a smart a$$. Just trying to understand completely, since that term is new to me.

edit:

I guess I should’ve researched it before bothering you Dan.

“A case drain specifically handles bypass or leakage fluid from a hydraulic component, while a return to tank line carries the main flow of hydraulic fluid back to the reservoir after it has been used in the system.”

I also found that the return to tank line can have restrictions in it caused by things like a oil cooler or a filter, whereas the case drain will likely be running at lower pressures since it will go straight back to the tank with nothing inserted in it…

 

[TheOldHokie]

Thanks Dan. So the case drain is then a separate path back to the tank, as compared to whatever line might be used for fluid exiting a cylinder? Or is it just semantics?

Not trying to be a smart a$$. Just trying to understand completely, since that term is new to me.

Your initial question signaled your confusion.

The case drain is separate from the implement tank return line. Thats why its often called a "third line". Look at the picture I posted earlier of the Case skid loader. The two larger lines are pump out and tank return. The smaller "third line" is the case drain. the case drain is isolated from the tank return People have been known to cheat by piggy backing the case drain on the implement return but its frowned on and does not provide the same level of protection.

Now let me anticipate your nextvquestion:

When Hydraulic Motor Case-Drains Are Optional—Unless You Want Reliability!

As you're hopefully well aware, an unrestricted case-drain line is essential on a piston-type hydraulic motor, whether it's axial, radial or bent-axis design. But when it comes...

www.powermotiontech.com

Dan

 

[Henro]

Your initial question signaled your confusion.

The case drain is separate from the implement tank return line. Thats why its often called a "third line". Look at the picture I posted earlier of the Case skid loader. The two larger lines are pump out and tank return. The smaller "third line" is the case drain. the case drain is isolated from the tank return People have been known to cheat by piggy backing the case drain on the implement return but its frowned on and does not provide the same level of protection.

Now let me anticipate your nextvquestion:

When Hydraulic Motor Case-Drains Are Optional—Unless You Want Reliability!

As you're hopefully well aware, an unrestricted case-drain line is essential on a piston-type hydraulic motor, whether it's axial, radial or bent-axis design. But when it comes...

www.powermotiontech.com

Dan

I really appreciate your help Dan,

I guess I was editing my post while you were typing so I came to the understanding that you explained in your last post… I really appreciate your own to help people here to understand hydraulics!

 

[TheOldHokie]

I really appreciate your own to help people here to understand hydraulics!

I miss teaching....

Dan

 

[xenophon.nl]

LOL… That highlighting looked familiar! I must’ve posted that image somewhere because I looked at my file for the KX-41-2V workshop manual and the highlighting is the same as I have here!

It is you replied on another post I made some time ago.

Installung a tee in a valve or motor return line is frowned on.

Dan

Both final drive case drain lines go into the swivel joint, on the top of the swivel joint I see a hose with a hose clamp, assuming this is a no pressure line. I also see a hose with a hose clamp on the valve block, a big line, assuming also this is a no pressure line, again assuming both go straight back to tank. I was thinking of tying in one of these. I highlighted both lines on the pictures included.

But as I understand from Dan, this is not the way to go?

 

[TheOldHokie]

It is you replied on another post I made some time ago.



Both final drive case drain lines go into the swivel joint, on the top of the swivel joint I see a hose with a hose clamp, assuming this is a no pressure line. I also see a hose with a hose clamp on the valve block, a big line, assuming also this is a no pressure line, again assuming both go straight back to tank. I was thinking of tying in one of these. I highlighted both lines on the pictures included.

But as I understand from Dan, this is not the way to go?

I really cant tell whats what in the pictures.

You use the term "case drain" for tje finsl drive motors. Jow do you know that is what it is? Does your manual call it that?

Like I said teeing into a normal return line is frowned on. Those lines can see several hundred PSI when an actuator is is powered and thats way too high. You are basically rolling the dice.

Dan

 

[xenophon.nl]

I really cant tell whats what in the pictures.

You use the term "case drain" for tje finsl drive motors. Jow do you know that is what it is? Does your manual call it that?

Like I said teeing into a normal return line is frowned on. Those lines can see several hundred PSI when an actuator is is powered and thats way too high. You are basically rolling the dice.

Dan

I actually replaced one final drive, and the manual states there is a case drain port.

I see now indeed you say to not tee into a return line, so it would be okay to tee into a case drain line?

Then my 2 options might still be possible. Because they are connected using a hose clamp I think they can not be high pressure lines.

I found a diagram on messicks (called oil piping (oil return)) of a version very close to mine, showing the lines more clear, it is '040' and 'A' on the picture.

 

[TheOldHokie]

I actually replaced one final drive, and the manual states there is a case drain port.

I see now indeed you say to not tee into a return line, so it would be okay to tee into a case drain line?

Then my 2 options might still be possible. Because they are connected using a hose clamp I think they can never be high pressure lines.

I am no expert but I think teeing case trains together will be fine. Might want to ask Google what she thinks. Those two drive motors may actually be teed internally.

Dan

 

[GreensvilleJay]

Case drains are NOT high pressure, just a dribble or so and hopefully not a lot of oil. Only time they could be 'high pressure and lots of oil is when the motor selfdestructs. You'll KNOW if that happens.

 

[xenophon.nl]

The flail mower I would like to rent has 2 connections, a pressure line and a low pressure tank return line (case drain? or is that something else?). But since it has 2 connections I expect a lot of oil going to the return line.

 

[TheOldHokie]

The flail mower I would like to rent has 2 connections, a pressure line and a low pressure tank return line (case drain? or is that something else?). But since it has 2 connections I expect a lot of oil going to the return line.

If it only has two lines it is a basic (unidirectional?) motor circuit with pressure out low pressure tank return and does not have a case drain. A case.drain is an additional "zero pressure third line"..

You started this thread saying the motor required a case drain. What made you think that?

Dan