Hydraulics on Kubota

Borrowed my buddies Kubota backhoe last week and noticed a problem that wasn't there last time I used it. Everytime i raised the hoe, it would drop about 12" before lifting. It has had some issues with some circuits being weaker than others (pressure relief releasing too soon) since he bought it last year. It is around 12 years old. Could it be low on fluid?? or could it be something more serious? I'm the one that usually works on his equipment but have very little experience with hydraulics as complex as on this.
Thanks for all your help.
Charlie

Should be a plug or dipstick on it somewhere for the hydraulic oil. Pull it and check. If the filter hasn't ever been changed it could be dirty. If that doesn't do it there could be a problem in the valves. Sounds like there is a pressure problem somewhere.

It could just be low on oil. It sounds like there is air in the system. The air bubbles make the system do strange things.

I agree with JD.

Sounds like air in the system.

Dean

Let,s back up. You say KUBOTA, they make tractors with backhoe attachments, Pure dedicated backhoe units and then mini excvators that lots of folks call backhoes. Do you have a model number of maybe the tractor or the backhoe. Twenty eight years KUBOTA experience. Just might be abel to help you if you will tell me what you have.

Turn the power steering all the way and hold it a short bit of time. On my B3200HSD, that maneuver is what Kubota says will clear air from the hydraulics. Worth a try.
Dave

Thanks,Its a L4310. The Hoe is powered by a PTO pump. We changed some hoses and the filter a few months back and it worked fine then. I could ease it up an inch at a time but now it drops when it should be easing up. One of the out riggers was always weak and struggled to lift the tractor. I can hear the relief releasing the pressure but thats a different issue than the present. I"ll check the oil level first, if its ok what would be the next thing to check??

I work for a Case/Kubota dealer but specialize in new Case hoes and loaders and was there when Case introduced their first hoe and loader. Most modern hydraulics as complex as a hoe and loader have load check valves which hold the backpressure from the cylinders till the oncoming pump pressure can lift the loadcheck off it's seat allowing a drop free lift. I would suspect a load check in the particular circuit that is dropping. We have replaced many in the Case skid steers for just what you are describing although a foot is more drop than I experience with those failures.

Changing filters is a maintainance issue and usually does not correct problems. When looking for problems often we cut filters apart to see if evidence of detrioration of packing or worse yet metal fragments which indicate deterioration of hard parts.

As previously stated, I work with full size wheel hoes and loaders but the same principles apply.

As simple as it may sound, if I had a weak circuit such as you describe with that stabilizer I would automatically look at the spool stroke to insure it was travelling full stroke in the weak direction.

I do not know about Kubota but the stabilizer sections on Case hoes do not have secondary reliefs. Just drawing on my years experience hopefully to point you in the right direction.

mEl

Well you still did not get me the actual hoe model. The hydraulic outriggers do have Load checks as the other poster suggest however the working sections like boom, bucket,arm ect do not have sectional load checks. If I understand you right it is only when you pick up the BOOM section it drops before it picks up. What causes that is the Large sectional O ring between the spool sections on the valve is leaking past. You are having to fill the valve before the work takes place. Couple of things to check Before you go in the valve. Raise the boom shut the unit off and check leak down.

Thanks JM, I dont know the # of the hoe but will try to lift it and turn tractor off and see what happens. If weather permits I'll try to go over this weekend and check it out. I'll post after I get a chance to check and tell what i find and will have the model # of the hoe then. Hopefully it wont require tearing into the valve but if it does, is there any how to on the net for these? I've found some general stuff but would like to have some Kubota specific if i can find it. It looks different from what I see on the older tractor loaders like I'm more used to. I sure appreciate your advice.

Charlie

Go to KUBOTA.COM select illustrated parts list, accept user agreement , type in the MODEL number of the HOE. You can see the parts break down there under hydraulic valve.