Just Discovered that Pump Out and Power Beyond hoses to Loader Reversed at Block ???

[Gordon Gould]

3 years ago I bought a used Kubota M5640 with 700 hrs on it. Since then I have added another 450 hrs. It has a L1002 Loader, a (WR Long ?) 3rd function valve, and a single Rear Remote. All part of the original package according to the seller. I am planning on adding some hydraulics and was out tracing the hoses to see what what was what. In the process I discovered the PO and PB hoses are reversed on the hydraulic block. Brings lots of questions to my mind to say the least. But I have had no problems at all. I need some input or advise from someone with more knowledge than me.

This is the way it is plumbed following the fluid flow path. Pump Out from the block goes to the Out port on the 3rd function valve. Power In on 3rd func goes to Loader valve Power Beyond. Power In on Loader valve goes back to the Power Beyond on the hydraulic block. So the flow thru the valves is reversed from what it should be. The Tank port on the Loader valve is OK. Is this plumbing OK ?? If not why is all good after over 1000 hrs. Should I switch the block lines. Has any unseen damage occurred ?? Thanks.

gg

 

[ptsg]

Would have to see an hydraulic diagram for that tractor to be 100% sure, but I think what saved you, is that most manufacturers will put a safety relief valve right at the hydraulic block on the flow path straight from the pump. Otherwise, once you used the third function valve, it would dead end the circuit and most likely crack the hydraulic pump or shear the shaft of the pump.

 

[Gordon Gould]

OK Thanks - if I understand, this is what you are saying - because the 3rd function valve is first the pressure relief in the loader valve does not fire and the relief pressure is controlled by the pump relief valve. Another question - if there was no loader valve, as it is an option, would the pump pressure relief valve be used to protect the system or are there other relief valves in the 3ph or rear remotes ??
In other words is it bad relying on the pump relief valve like I am now ??

gg

 

[ptsg]

So most systems are setup like this: Pump -> Hydraulic block -> loader valve -> 3rd function (if fitted) -> remotes > 3pt valve. Some tractors may vary, so don't take it 100% for granted.

The hydraulic block, loader valve, remote valve, 3pt valve will have a safety relief valve. Basically one per component. The 3rd function, depending on what valve they used, may or may not have a relief valve. Usually the solenoid operated 3rd function valves, don't have a relief valves.

The 3 pt system actually have two relief valves. One for the valve that limits the max pressure and another one connected directly to the cylinders, so if you hit a bump hard with a heavy implement in the back, the relief valve gives before something breaks.

It's always a good thing having all the relief valves able to work, in case one or another get stuck or something weird happens.

One way or another, I believe I answer your questions. Hopefully I wrote that in an understandable way.

I would fix your system. Put the loader valve first, then 3rd function, and the rest is already good to go.

 

[Gordon Gould]

Thank you for taking the time for a teaching session ptsg. That was a very clear and helpful explanation. And I will be changing it around like it should be.

gg

 

[Gordon Gould]

Thinking about this and trying to get it all straight in my head how hydraulic valves work I have another question - If the flow thru the Loader valve is reversed does that put the loader valve relief down stream of the work ports so that the loader components are not protected by it ?? If so their relief would come from the pump relief valve also. Or does the Loader relief valve see pressure any where in the valve body so it would still be protecting the loader components ??

gg

 

[Rustyiron]

Gordon I wonder (if I understand your description properly) that if you're 3rd function is fed first, and reversed, if it's as simple as your control buttons are reversed in their operation?

 

[Gordon Gould]

That's the thing - nothing is obviously wrong. Every thing seems to works as it should. I'm just wondering out loud here about what might actually be happening to make it seem like nothing is wrong. If the weather co-operates tomorrow I am going to take some pressure measurements and then change the plumbing around to the way it should be and see what changes.

gg

 

[ptsg]

If you could find a workshop manual with the hydraulic diagrams would be awesome to make sure of the order of the components.

 

[Dave M7040]

What are you calling a hydraulic block? I do not see one listed on parts illustrations.

It is easy to get confused when hydraulic components are connected together.

One valve's IN is fed by another component's OUT.

I have been told by Cross Manufacturing's tech specialist if that if the P (Pump out) and PB hoses are swapped the valve will not operate properly.

No, it will not operate properly. When the spool is shifted the Power Byd is blocked.

Thanks, Jeff


I doubt you have circuits improperly connected. Only change them after great study. In hydraulics, expensive components are destroyed in fractions of a second. It is not a "Lets try and see what happens," world.

Dave M7040