Hopefully I can get some assistance here. I have a fairly old Kubota L3130E 2wd roughly 20 years old. The 3 point hitch has started to hunt (or bounce if you wanna say) when it is picked up with weight on it. I can close the lowering speed adjustment and it quits and it won't bleed down, if I open it it starts back and it will bleed down when the tractor is off. I have replaced the position control valve, put seal kits in both lift assist cylinders, replaced the large check valve to the right of the lowering speed adjustment valve on the hydraulic block under the seat and I have changed the hydraulic fluid and filter with Kubota brand filter and oil. I am at a lost on what to do next. Seems like I'm fighting a losing battle with it. Any tips on where I should look next? Any help is appreciated.
Kubota L3130E 3 point hitch hunting (bounces)
- Thread starter Holtondale90
- Start date
TheOldHokie
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L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
I know nothing about the specifics of that system but it sounds like the main control valve may be leaking. That causes the 3pt to sag which activates the position control circuit and the lift returns to the set height. Cycle then repeats.
Dan
+1 Since it stays up when the speed control is closed, it's not the cylinder leaking. My BIL's little Ford did this when his brake linings fouled the valve.
I guess I need to figure out which valve you are both referring to then I've looked at both manuals and haven't seen a valve called that in their diagrams
RCW
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BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
I would also look at the feed back rod/lever. Might be out of adjustment, causing the hunt/bounce. Allows the tractor to "know" orientation of the rock shaft.
Look at Hydraulics section of the Illustrated Parts Diagram here.
Kubota Tractor Corporation - Illustrated Parts List (kubotausa.com)
Should be able to finds tips for the Feed Back Lever's adjustment in the Workshop Manual, that can be found here.
Kubotabooks.com
Look at Hydraulics section of the Illustrated Parts Diagram here.
Kubota Tractor Corporation - Illustrated Parts List (kubotausa.com)
Should be able to finds tips for the Feed Back Lever's adjustment in the Workshop Manual, that can be found here.
Kubotabooks.com
The only valve referred to as a control valve is the Position Control valve that mounts to the bottom of the hydraulic block. That is brand new. It was the first thing I replaced.
RCW
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BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
RCW
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Equipment
BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
Okay - - did you have the WSM for pointers? The one I linked is free....
Not disputing the opinions of Dan or PoTreeBoy at all. Both very smart guys.
Just when I see/hear of 3PH getting funky, oftentimes Feed Back Rod can be culprit, as it can interfere with continuous operation through the limits of travel.
Do you hear it go to bypass when it bounces? Do you hear sounds at the valve the other guys were speaking of?
No noise of any kind actually. Only time I heard bypassing was when I was adjusting the feed back rod to the point where it opened the valve. Then as the manual says I back it off a few turns worked it up and down still bounces. No also to note, I can get this to bounce by just using my body weight to push down on the arms. I'm not using an implement right now until I get the bounce fixed so it doesn't take alot of weight to make it start. It also doesn't bounce when there is no weight applied
RCW
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BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
Will do. Just wanted to throw it out.
I've wrestled with the governor linkage on an early-50's Minneapolis Moline. They can be a pain and very finicky.
I've wrestled with the governor linkage on an early-50's Minneapolis Moline. They can be a pain and very finicky.
This whole system can be finicky. Also another note here I forgot. This tractor was given to me by my brother in law. He went out and bought a new one since this one was having these issues. My dad used it for a while and put way to big 9f a box blade on it and the 3 point hitch would not rise at all with out weight unless the tractor was at full throttle. That problem got fixed after I replaced the whole position control valve. So now I'm just back to the original problem.
RCW
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BX2360, FEL, MMM, BX2750D snowblower. 1953 Minneapolis Moline ZAU
I would go back to the previous recommendations.
When I said the other guys were pretty sharp, was meant in all sincerity.
Wish you the very best in getting it figured out. There is a fix…..
When I said the other guys were pretty sharp, was meant in all sincerity.
Wish you the very best in getting it figured out. There is a fix…..
I don't have an answer, but do see what is happening in my mind...
The 3PH is stable without any weight on it.
Put weight on it and the position control system reacts. Why would this happen? Because the position of 3PH dropped, and the system reacted to put it back where the setpoint is.
Now how can the 3PH drop? Likely not due to a piston/seal issue, since when the valve that controls the speed of dropping prevents movement when it is closed.
So the 3PH is dropping because fluid is leaking out of the cylinder somehow. BUT the cylinder is apparently good, as proven by the drop-rate valve closure.
So where is the fluid going? No leaks right?
BUT you replaced the control valve. Where did it come from? Is it a new Kubota part? Or?
Viewing the situation from the control system perspective, the 3PH must be lowering because of weight added, above the weight of the arms and other hardware, since it does not oscillate when unloaded.
Again, no leaks right? So where is the fluid that is expelled by the cylinder going, when the 3PH lowers due to applied weight? Could there be a leak somewhere that only comes into play when a certain amount of pressure is developed in the circuit that holds the 3PH in place? This would be my guess.
I think this is the question that needs to be answered. Stay focused. Dan ( TheOldHokie) and others can give you great help.
The 3PH is stable without any weight on it.
Put weight on it and the position control system reacts. Why would this happen? Because the position of 3PH dropped, and the system reacted to put it back where the setpoint is.
Now how can the 3PH drop? Likely not due to a piston/seal issue, since when the valve that controls the speed of dropping prevents movement when it is closed.
So the 3PH is dropping because fluid is leaking out of the cylinder somehow. BUT the cylinder is apparently good, as proven by the drop-rate valve closure.
So where is the fluid going? No leaks right?
BUT you replaced the control valve. Where did it come from? Is it a new Kubota part? Or?
Viewing the situation from the control system perspective, the 3PH must be lowering because of weight added, above the weight of the arms and other hardware, since it does not oscillate when unloaded.
Again, no leaks right? So where is the fluid that is expelled by the cylinder going, when the 3PH lowers due to applied weight? Could there be a leak somewhere that only comes into play when a certain amount of pressure is developed in the circuit that holds the 3PH in place? This would be my guess.
I think this is the question that needs to be answered. Stay focused. Dan ( TheOldHokie) and others can give you great help.
Everything I replaced on the tractor was kubota parts that I ordered through my local dealer. I did re build both of the 3 Point cylinders but all I replaced was the piston bushing and gasket and then the scraper for the rod. This is what the dealer said would be in a seal kit if I were to buy one but they do not make seal kits for these cylinders anymore due to them being replaced due to issues they were having with them. That is what the dealer told me anyway. Only thing I can figure is that the problem is still in both cylinders and I just didn't replace the correct part. No visual oil leaks from any connection. I checked for that after replacing the position control and after rebuilding the cylinders.
it almost sounds like the drop speed adjustment knob is leaking somehow (check valve?)--but you said you replaced that. How'd the check valve bore look? Nicks, cracks, dings, dirt, etc? It all has to be squeaky clean.
only other thing I can think of is perhaps the adjustment ON the position control valve is misadjusted; kubota gives a specific measurement for it and you have to stick to that, in my experience 0.5mm either way will cause some issues. OR-maybe there's some dirt in the position control valve? Piece of an o-ring? Is the valve the newest version or is it a used one or? It was updated at some point in the last 20 years, one of the little spools inside had a tendency to stick--and this seemed to be more common when using any fluid but super UDT(2).
only other thing I can think of is perhaps the adjustment ON the position control valve is misadjusted; kubota gives a specific measurement for it and you have to stick to that, in my experience 0.5mm either way will cause some issues. OR-maybe there's some dirt in the position control valve? Piece of an o-ring? Is the valve the newest version or is it a used one or? It was updated at some point in the last 20 years, one of the little spools inside had a tendency to stick--and this seemed to be more common when using any fluid but super UDT(2).
Numbers 100, 80, 130 and 050 are what I replaced on both cylinders.
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It was a brand new valve supposedly the "new" style. As for the check valve the old one that came off looked fine from what I could see. No trash. Oring and Teflon backing ring were okay from what I saw. I replaced #40 in the diagram I attached. This was the last thing I have done/ replaced.
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TheOldHokie
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L3901/LA525, B7200DT/B1630, G2160/RCK60, G2460/RCK60
As I said earlier I know NOTHING about this particular system but your description of the symptoms suggest something in the lift circuit is leaking causing the position control system to oscillate and the 3pt height to hunt.
On some tractors Kubota had a separate position control valve but looking at the workshop manual this does not seem to be the case on your model.
I think Henro explained my thought process pretty accurately. The lift circuit is likely bleeding off pressure somewhere and the position control feedback linkage is adjusting in response. Its also possible the feedback linkage is simply misadjusted and it is over shooting on the correction and then correcting again in the opposite direction.
You asked for thoughts and that is the best I can do.
Dan
I apologize if I am coming off in any way. That was not my intentions at all. I am just doing my best to explain everything I have done thus far. My apologies.