Some hydraulics not working

B2920

I was plowing snow a couple of weeks ago with a rear blade on the three point. At the tail end of my plowing, I found that the blade was lifting very slowly. Eventually, it would not lift at all. HST was no problem. Temperature was just about freezing, so I would not suspect any water in the HST. And the problem continues now that it is 45° or more.

I made it back to my shop, dragging the blade the whole way, checked to ensure that the hydraulic fluid level was fine, and did some tests. I found that I could not raise the blade or FEL bucket. But I can curl the bucket, and if I engage the bucket raise while curling the bucket , I can raise the bucket simultaneously and even continue to raise after stopping the curl. Even then, though, I still cannot raise the blade. I loosened the three-point limit bolt/plate to allow the lever more travel, but still no lift on the three-point.

On the advice of my local Kubota shop, I shut it all down, disconnected & reconnected every hydraulic quick release I could find: I think it was four going to the FEL and one at the rear--the one that I would disconnect and connect to the backhoe. There may be others; I did not dig very deeply yet.

Earlier in the summer, we had rolled a branch up and broken off the HST filter stud on the left side, so I had replaced the filter and stud with base. That is, I do not suspect a plugged filter, since I just replaced it maybe 2-3 months ago.

It seems like this might indicate a stuck relief valve. If so, where is it, and why would it behave like this--unable to raise 3-point but always able to curl the bucket and able to raise bucket only during/after curl?

Thank you.

Now, physically, where do I want to start looking. I am not a mechanic, and hydraulic details are somewhat new to me. I just did not want to have the Kubota dealer's mechanic come out to fix this until I could determine if it was something actually significant.

I have verified that the three point lever moves smoothly without binding, and that entire linkage is fairly short and entirely visible. The bucket lift lever does tend to stick occasionally in the activated position (that is nothing new) but is easily un-stuck with a little extra pressure. Given that I was plowing in perhaps 12" snow when this occurred, the entire undercarriage would have been in the snow and potentially liable to having a stick in the snow shoved pretty much anywhere. I am just not sure exactly where else to look for any linkage problems.

Sorry about the delay here. I had called the local Kubota dealer, and they said it sounded like a bad coupler. I uncoupled and recoupled everything, to no avail. I finally hauled the tractor over to the shop and left it there for a week and a half. They were busy and could not get to it for over a week.

But when I called to check on the status a week later, I talked to the mechanic, and once I described the problem, he reiterated his suspicion that it sounded like a coupler. An hour and $37 later, it was all fixed. It was a bad coupler at the backhoe connection. I did not have the backhoe attached, and when it is not attached, of course, that hose functions purely as a return.

It is not too surprising that they had a quick fix for something that seemed like a mystery to me, given that I do not understand hydraulic routing all that well. After all, I manage business computer networks for a living and they sell/repair Kubota tractors. I appreciate the help here, as always, and perhaps my experience can be of some help to someone else later.