Loader valve

[Harry in Ky]

I'm aware of the loop line, but that's not the point. If the three point is not used while the backhoe valve is connected, then it makes no difference, I agree on that. However I don't know how his hoe mounts. Some backhoes are mounted on the three point, so it's possible to apply a load on the lift while the valve is connected, whether it's in use or not. That subjects the backhoe valve spool seals to whatever pressure the lift develops. If that's the case, then he's been lucky so far. Others may disagree, but that's not the way I was taught to do it.

 

[K5lwq]

You are correct except for there is no spool seal. It is a machine fit. If the 3pt was use the way it is plumbed then the back pressure could crack the valve because the the tank port is designed to handle flow pressure only.

We are saying the same thing but most likely the 3pt will be locked down in this case. Either way the OP should not try to use the 3pt when the backhoe is connected.

 

[Harry in Ky]

You can stand by that if you wish, but I have yet to see a control valve that doesn't have at least an O ring on each end. Those are placed there to seal only low pressure, and the area behind them is open to the return passages of the valve body. They aren't expected to be subject to working pressure, as that is, by design, contained by the precision fit of spool to body tolerances. If you disagree with that so be it. You can have the last word.

 

[ptsg]

You can stand by that if you wish, but I have yet to see a control valve that doesn't have at least an O ring on each end. Those are placed there to seal only low pressure, and the area behind them is open to the return passages of the valve body. They aren't expected to be subject to working pressure, as that is, by design, contained by the precision fit of spool to body tolerances. If you disagree with that so be it. You can have the last word.

The O-ring for the spool is there to retain any small leakage that may appear through the close tolerance between the spool and the bore. It also prevents outside contaminants to from getting inside the spool. Some valves also have a wiper.

On my homemade backhoe, I've been feeding the backhoe control valve using the Tank port of the drive control valve ever since I built the machine a looong time ago. I do have separate main relief valve right after the pump. So far, I've absolutely 0 issues with doing it this way. Is it correct? Definitely not but it's just to say that the o-ring on the spools does not see any high pressures at all.

 

[Harry in Ky]

Okay, but I'm not sure how that applies to what this discussion is about.

 

[SBC]

Oh man, I've used the rock shaft a bunch of times with the backhoe on. What is the issue with that?

The schematic shows the out port as optional? Why do I need an outlet to the tank? Not doubting just looking for an explanation. Should I T into where the backhoe returns?

 

[Harry in Ky]

Wow! I can't believe this has gone on this far. Typically, I glance through the day's posts, and look for anything that looks interesting. Usually not much, I might add. Any threads with more than four or five replies I don't even look twice at because they often have a bunch of replies from guys just bickering back and forth over something more than likely not truly related to the subject that started it all. Here I am doing exactly that.

SBC, I have no idea how/where your backhoe valve's supply and return lines connect to the tractor so I have no comment for you at this point. It's entirely possible your system is nothing like the one pictured here.

As for the other subject discussed earlier, it isn't about how the valve is supplied, only about how fluid returns to the tractor and under what pressure.

 

[K5lwq]

I marked your picture of the old loader valve with what I think the connections are. You would want to tee into the port I marked T for tank with a hose from your new valve marked T.

P=Power In
T=Tank
PB=Power Beyond

Hope that clears it up. If not I will try to help.

 

[Noradavis]

Hydraulic control space bar clicker valve for tractor loader usually consist of a spool inside a cylinder which can be mechanically or electrically controlled. The movement of the spool restricts controls the fluid flow. ... Because simple application of electrical power provides control, these valves are used extensively

 

[rScotty]

Good afternoon and Merry Christmas! I have a John Deere 950 with loader and power steering. I'm adding a Brand hydraulics loader valve to replace the existing worn loader valve. I plan to keep the existing loader valve in place and use it for remotes in the future. The Brand valve I've purchased is configured with a power beyond port, an "in" port and an "out" port. I will be tapping directly to my hydraulic pumps outlet. My question is should I use the "out" port or the power beyond port to feed the tractor downstream from the valve? Thanks in advance for your help and consideration!

Hello, I've participated in some hydraulics threads here, but it looks like you are well along. Please do post what you find and the results so we can all learn. .

Before you even get started, it might pay to take a look at a detailed hydraulics diagram in your JD950 Shop Manual. Many - not all - Yanmar products from that era had a Power Beyond outlet as an option. If yours did, it would be located on the rear casting just to the side of the 3pt speed adjusting knob under the seat. On models that had that option, all it required was removing a fitting & replacing one internal sleeve with one for power beyond....same as you do on loader valves to use the PB.

rScotty