Hydraulic Damage?

GregJ · Jan 5, 2003

I had an experience this afternoon that I'd like to ask the group about, since I am a complete novice when it comes to hydraulics. I was doing a lot of backhoe work and I was getting on and off my B7500 many times. At some point, I inadvertently hit the 3Pt lever in the up position. Later in the afternoon I went to use the loader and found that it didn't have any down pressure. I had up, curl and dump, but no down. The only only way I could lower the bucket was to float it down. I figured it was a stuck valve or something similar. I continued with some more backhoe work and even did a little loader work, grading a small area. As far as I can tell, I must have had the lever in the up position for at least 2 hours of operation. When I backed it into the shop, I realized what I had done, moved the lever to neutral and the loader works fine. Obviously the 3pt hydraulics were robbing the loader of enough pressure to operate fully. My limited knowledge about hydraulics tells me that I just had the relief valve open for an extended period, which is not good, but not harmful, but I'm not sure. Could I have done any damage? I know I'll sleep better tonight if an expert were to tell me that things are ok.

Thanks,
Greg

Charliebrn · Jan 5, 2003

Your 3pt lever has a spring that if properly adjusted, returns the lever to Neutral one the 3pt is in the highest position. Check that adjustment, and that should prevent this from happening again.

techman · Jan 5, 2003

Greg:

You didn't do any damage. Our Kubotas have a single constant volume pump that feeds all of the accessories. Each circuit is basically "wired in series". There is a valve in the some systems called a priority valve that will let some circuits take a fixed oil flow and let the others use whatever is left over. On the BX's the priority circuit is the steering, which has priority over all other systems. I believe that the 7500 has a separate steering pump so that priority circuit isn't needed.

In your case the 3pt was the first user in the line and it seems to have used up oil when active, starving the other circuits.

Properly designed systems (which the Kubota is) makes it nearly impossible to damage any hydraulic components. The only real harm possible is if you push over a relief valve for a long time it can generate enough heat to break down the hydraulic fluid. Do a quick look at the fluid. If it is dark brown and smells a bit burned, you should change it soon. Otherwise you should be fine.

paul

GregJ · Jan 5, 2003

Paul,
Thanks a lot for the explanation. I feel better now, however I am looking at my lever and spring adjustment. I have attached a photo of the spring in the full up position. The threads end right where the spring starts, so adjusting the nuts all the way down would still not put any pressure on the spring. I may be missing a part or something. I don't ever remember the lever self centering. I think I'll call my dealer tomorrow and talk with him about it.

Thanks,
Greg

bellweather · Jan 6, 2003

Greg
If it makes you feel any better. I had the same thing happen to my BX22. Like you, I discovered that I could raise my FEL bucket but only lower it using the float position...then I discovered that my 3-pt lever did not return to the neutral position, as it is supposed to (says so in the manual). Now I always check whenever I move it. One day I'll get the lever fixed properly.

PS - no harm done to the tractor...far as I can tell.

GregJ · Jan 7, 2003

Just a followup. I dropped by the dealer today and studied the purpose and function of the spring on the 3pt control linkage. The spring only engages when the 3pt is at the top of it's travel. With the backhoe on, the 3pt never moves, so the lever will never return to the neutral position. He also told me that this is one of the most common "service" calls they have on loader problems. Maybe he was just trying to make me feel a little less stupid. At any rate, no harm done. Whew!

Greg

bellweather · Jan 7, 2003

For what it's worth, my lever doesn't return to the neutral position even with the BH off, which suggests there is a problem witht the lever-return-mechanism...on my tractor that is.

GregJ · Jan 7, 2003

Actually, after the service manager showed me how that spring worked, the adjustment is really very simple. If the BX22 is the same principle as the B7500, the linkage travels on a guide when the 3pt. raises. ( See photo attachment above) When it is at the top of it's travel, you should be able to tighten the nut until the spring pushes the lever back to the neutral position. I couldn't see that until the dealer raised and lowered the 3pt. Then it all made sense.

Greg