Onboard Hydraulic Grenade

[chrisinnh]

It sounds like you may have hooked the loader valve up backwards.

I hope so!

The relief valve is always (far as I know) on the inlet side. If you hooked it up with the "IN" hose going to the "OUT" of the valve, then when you operate the controls, you are isolating the relief from the fluid. Any over pressure can't be relieved and the weak spot is located with much fan fare and excitement.

I'll be posting pictures in a few minutes. Hopefully you can comfirm that I've gotten it wrong

A second thought, your selector valve. If you operate the selector valve while the tractor is running, it may dead head the pump. Instantly killing it. Don't know if that is the case or not here. Just something to beware of.

john_bud, that is a very interesting thought. I'll be testing the selector valve to see if it blocks incoming flow at any point in its travel. I don't need any more ways to kill my pump

Your hyd diagram does not include the BH circuit. There may be a relationship there, don't know for sure.

No, the backhoe is a closed system with its own pump, tank, fluid, etc. ...And it's sitting under a tarp behind the garage.

That was actually the motivator to this whole catastrophe: I needed to remove the backhoe to install a snow blade on the rear, but didn't have any way to power my loader without it.

Also, I got the impression that you put the pump on replacing the function of a PTO pump. Did I read that right? If so, the fluid may be too thick for the pump. Check with the pump mfg to be sure. Over pressure situations can occur even with an operable relief valve if the viscosity is too high. Basically, the fluid can't get out the relief port fast enough to drop the pressure. Again, may not have a bearing on the case. But good to know.

No problem there, this is the pump Kubota hung on the side of my motor 30 years ago. And it's pumping the same 80W gear oil that it's been pumping since the beginning, including all winter last year.

My meddling in this system is the diversion of fluid away from the 3pt hitch lifter (the only use for that pump) and into the FEL.

Thanks very much for your help.

/chris

 

[chrisinnh]

Okay, more pictures of my bad plumbing for your entertainment

Here's a shot of the pressure line entering my loader control valve (selector valve barely visible below):

And here's the return to the gearbox side (obvious from the heater hose and clamp, I think):

Note that it says "OUT" on this side. That's why I hooked it up this way. Seemed reasonable at the time...

That thing on the right, closest to "OUT" is what I've been assuming is a pressure relief valve.

Here it is with the cap removed:

I'm hoping for some opinions:

Did I hook up the valve backwards?

Is that thing a pressure relief valve?

I didn't take it apart any further than shown because I didn't want to risk screwing anything up. That cap/locknut/screw setup looks very adjust-y.

Thanks for all of the feedback so far!

/chris

 

[Wayne County Hose]

I'll let the tractor guys here comment on the hose positioning as they are far more experienced than I. As far as hoses bursting, all hoses have a 4:1 safety factor. A hose rated for 4,000 psi has a burst rating of 16,000 psi. Hoses also have some give, pump castings have no give.

 

[JerryG]

Chris,
Before the pump gave it up. Was there any change or fluctuation in the RPM at all when you were raising or dumping the loader without a load on it when you let off of the handle? If there was, did it go up, down etc and about how much? I hope that wasn't to mudded.
(Raising the loader empty. Let off the handle. What type of movement in the RPM when let off?)

 

[hayden]

I think you have it hooked up backwards. On everything I've seen, the relief valve in on the input block, and when activated diverts to the output. The puzzling thing is the "out" on the block. I can't explain that.

If at all possible, I'd put a gauge on the system after the pump and before anything else. Then very gingerly activate your hydraulics to test it. Your relief valve may just need adjusting too. It sounds like until now the backhoe relief valve has been doing all the work. If you note the position of the relief valve screw, then back it off counting the number of turns or half turns, you will be able to get back where you started.

 

[john_bud]

Chris,

As Hayden said, it's not a standard valve flow path. Not to say it's wrong. You may have to take off the inlet and outlet blocks and post pictures of their inner surfaces. Is there any marking of "in" on the other side?

I'm not an expert, there are real experts that deal with this daily. Maybe one of them can chime in?

Here's a link to a typical loader valve.
Surplus Center Item Detail

The left most control handle is for the boom and has the float spool. The right most handle is for the bucket curl. The Right most side has a large hex plug. That's plugging the power beyond port. Next to it, is the outlet port for fluid back to the sump. The LEFT side is the inlet side and that little stub thing sticking out looking almost like a 3rd spool, is where you would adjust the relief valve. That's typical standard common what you see every day when you look at most tractors.

Hope that helps.

jb

 

[ccsial]

The thing with the screw must be either a relief valve or flow control. I'd bet it is the relief. You could take it off and see how it is ported. That should tell you.

In any case, when it is fixed, I'd switch to all UDT. There must be a reasson kubota changed it. Maybe cold WX. As John Bud mentioned, viscosity can cause extreme pressures.

First though, you have to figure out if it is backwards. Expert opinions?

 

[chrisinnh]

Chris,
Before the pump gave it up. Was there any change or fluctuation in the RPM at all when you were raising or dumping the loader without a load on it when you let off of the handle? If there was, did it go up, down etc and about how much? I hope that wasn't to mudded.
(Raising the loader empty. Let off the handle. What type of movement in the RPM when let off?)

I didn't notice any change in the RPM. The motor was probably turning around 1400 (I don't have a tach) at the time, but was under (pretty much) no load.

I think my hand was still on the levers (one forward, one back) at the moment it broke.

 

[chrisinnh]

The puzzling thing is the "out" on the block. I can't explain that.

Is there any marking of "in" on the other side?

Looking carefully at the pictures of the other side (I haven't been back out to the garage yet) I found this:


I think both sides might say "OUT".

Maybe both ends of valve are made from the same casting?

If I switched my hoses around, I'd have the inlet hose on the unmarked end of the opposite casting, and the outlet hose right here where it appears to say "OUT" in the photo above. That would put both the relief valve and the tank return next to an "OUT", which makes sense.

/chris

 

[KubotainNH]

Good pictures are always helpful. It looks like both sides of that unit can be removed and swapped. So you could remove the relief valve and put it on the other side where I think it should be. Maybe not all valves are built the same but mine flows from left to right with the inlet on the left and the outlet on the right. Yours looks like it's made to allow the stacking of more spools. I think someone hit the nail on the head when they said the hoe relief valve was doing all the work. I have pics of the setup on my b6100 on this thread: http://www.tractorbynet.com/forums/kubota-owning-operating/70830-b6100-picture-3.html