LA272-1 Hydraulics Control Issues !!

[csdifani]

Folks:

We have a B7510 with a LA272-1 front loader. My wife arrived (she's the tractor operator.... and I'm the tractor fixer) at the shop complaining of the front bucket lowering very slowly. My wife has a small organic orchard (352 trees...), and she loves her Kubota... and every attachment that she has for it, so when it's not working "properly", my priorities get immediately rearranged.

The problem started without any symptoms, went from perfect operations to not in a moment. I checked the hydraulic fluid level, and everything else I could think of. Everything was "right", no leaks, not a lot of "slop" in the control linkage, and the bucket circuit works perfectly (tilting up and down). The forks raise correctly, but lowering is the problem.... as in it doesn't... except when you push the control stick up thru the detent and the bucket "falls".

I found the thread from "Butch" in 2010, which is why I'm posting here. I'm hopeful that you folks have a suggestion or two on where I need to be going... workbench, lathe, mill, parts house, eBay, etc.

Her B7510 has 860 hours on it, and she's the "second" owner. All the preventive maintenance gets done, and it's got it's own stall in the barn. One thing I don't know (from the thread info) is which valve body we have. I didn't find a serial number on the valve body either, but I wasn't looking real hard at the time (serial# for the LA272-1 is 53287)

The valve body looks good; no leaks, no apparent damage or problems. And the same with the hydraulic hoses and cylinders. I did change the hydraulic fluid and filter last winter (when I also serviced her 4672A backhoe attachment), and didn't see any noticeable corrosion, or contamination in the old fluid.

But there is something obviously wrong... and most likely it's in the valve body.

Thanks for your time for reading this, and for your expertise in telling me the (probably/hopefully) simple fix!

Chris Difani

 

[North Idaho Wolfman]

Very likely it's got a bad disconnect.
Swap fittings on the lines and the valve for up/down and dump/roll back and see if you get any change.

 

[csdifani]

Excellent idea!! And I'll do that just as soon as I return this evening!

Thanks for the great diagnostic thought!!

Chris

 

[csdifani]

Wolfman:

So much for the "quick test" concept. I forgot about Asian pear harvest.... all of which means I just now switched the hoses at their QD connectors. I did find one "issue", there was a broken O ring stuck in the center of the male QD for the bucket (fitting marked "blue"). I used a probe and depressed the center down, and pulled the O ring out. It was broken, but otherwise seems to be complete. Small O ring, ring material about 1.5MM in diameter, and maybe 10-13MM in overall diameter.

What's odd about this "O ring" is that the circuit it controls (bucket) works perfectly. Not sure how it could migrate thru the system. One thing is that there is no external leakage of fluid from anywhere. Which means this 'ring must have come from somewhere inside... on the "interior".

Thanks again for the thoughts,

Chris

 

[Tooljunkie]

If i recall, the quick connect has o rings internally, to seal when disconnected. Its either that or one of the o-rings from the coupler itself.

I recall a similar instance, hydraulics mis-behaving, three point lever all the way up or aux hydraulic activated and not connected to anything. Another is the detent in the hydraulic control,rusting and balls falling out of their home and binding control. It also would snap into float. But more difficult than usual.

 

[csdifani]

Frank:

Thanks for the thoughts. I pulled the hydraulic control off, and found that there was no rust, water, dirt, corrosion, etc., in the system (hooray for preventive maint!). Unfortunately the one thing I did NOT do is check the 3 point control position. Right now I've got the backhoe attachment on, and the 3 point control may very well be part of the problem.... which means I need to put the hydraulic valve back together, and try it. The only tricky part I've got to deal with is that when the control valves slid out, they had a single O ring sitting on the bottom passage (narrow part of the valve shaft). I think it will be "fun" getting that O ring back in to the correct location.... not.

Thanks again,

Chris

 

[csdifani]

Re: LA272-1 Hydraulics Control Issues- Solved!!

Guys:

First of all thank you all for your thoughts, and diagnostics. It's really nice to have a "source" to come to when a problem occurs.

Now for the solution!

It turned out that it was "operator error". I had the backhoe attachment on the B7210 when this problem started. And the 3 point control was in the "rear" position. The control lever had gotten pushed to the rear... and it stayed there. Since the backhoe was attached (and it bypasses the 3 point lift arms), the position of the 3 point control lever wasn't important... and then I discovered that the entire problem was that darn 3 point control being in the wrong position!

I found a hint to this problem on one of the other Kubota forums, and since it was a "cheap and easy" test, I reassembled the front end loader control system, started the Kubota, centered the 3 point control lever, and moved the front end loader up, and DOWN. It WORKED!

With the 3 point control "centered", the front loader worked perfectly! No more problem with lowering!

Which makes no sense to me.... but I can't argue with success! I think hydraulic control circuitry is about the same as electronics... kinda like magic...

Thanks to all,

Chris