hi folks, need some help from experts here. i have a 90s b1750 hydrotstatic tractor. all hydraulics on the loader and power steering work fine with plenty of power. seems to go into pressure relief fine. problem is the 3 point hitch wont raise at all unless i bottom out the lowering speed valve, even then it will only raise empty. i can hold the lift arms back with one hand. i have replaced the piston and seals and dis-assembled the 3 point valve and inspected/cleaned. all seems ok. the linkage in there for the feedback rod is all in tact. i have run the function with the cover above the piston completely removed. there seems to be plenty of volume of fluid coming out of the port that feeds through the cap, but i can actually hold back the flow with my thumb. i can also stop flow with my fingers right at the banjo fitting where fluid feeds the 3 point valve. it seems theres plenty of volume there but it i cant get any pressure to build in the 3 piont section. the flow here comes from the same valve/block that the loader and power steering comes from and all that is good. i have removed the divider in that valve and it visually looks fine but im not sure how that is supposed to operate? anyone have any insight on what could be wrong?
3 point hitch wont lift
- Thread starter ronr
- Start date
Is this tractor new to you?
Did it ever work correctly, since you've owned it?
If it used to work, did you work on or change anything about that time? We're you using it when it quit working?
I know my B8200 has a valve you can rotate to direct flow to either the loader or the 3pt. I don't know if your tractor has that but i'd sure go looking. I almost hate to say it but if that valve exists on your tractor, it's possible the fix was as easy as turning the knob. 
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Did a little google search.. not sure what you mean by divider, as there is probably some kind of priority valve/divider for your steering circuit and im not sure whether you're talking about the same thing i'm talking about here, but..
There certainly appears to be a valve there, with a bolted cover preventing it from migrating on its own. Since you have a loader that bolted cover might be gone and the loader hooked up there. Did you try turning this valve?
There certainly appears to be a valve there, with a bolted cover preventing it from migrating on its own. Since you have a loader that bolted cover might be gone and the loader hooked up there. Did you try turning this valve?
yes that is the valve im reffering to, on the bottom side there is a divider valve for the PS versions. i did change that selector, which closes off the ports to the loader. it appears thats all it does. it may have made a slight improvment not having fluid flow to the loader but barely noticeable. #5 in the schematic you posted is the divider im reffering to. the parts schematic shows that port being capped off with no valve on MS versions. im thinking this valve works to give priority to steering if the steering is called for while the 3 point is also calling for fluid? im thinking there is where my problem is. maybe it's not allowing any priority to the 3 point at all but im not sure how to comfirm this?
This is kinda out of my wheelhouse.
Your tractor has HST, power steering and a loader, right?
And the loader works strong, right?
That diverter is to direct flow to the 3PH when there's no loader or other accessory installed. When it's turned, it blocks the bypass so flow goes out one of those plugged openings to the loader and back in the other to the 3PH. If you turned the valve with those ports blocked, you'd dead,-head the pump - that's the reason for the guard plate.
There's a WSM available on KubotaBooks.com, but the manuals on these older models is lacking in some areas.
There's a bypass valve under the seat of some models. I don't remember exactly what it does, but it's something to do with the 3PH. My L35 has it, but it's not used, since there's another bypass for the backhoe. Anyway, it has a screwdriver slot and you can try turning it if yours has one.
Since you've described good flow at your lift cylinder, I'm inclined to think you have an issue with the lift valve - o-rings or seals?
I'll try to do more research. In the meantime, maybe more knowledgeable folks will check in.
Edit: Looks like the valve under the seat would accomplish what your diverter does - bypass the loader. Yours probably doesn't have one under the seat.
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Yes the flow to the 3pt valve is there, but it's not building pressure. Seems like some part of the system prior to the 3pt valve is not switching. I can't help but think it's in that block that the loader lines and PS line connects in just don't know how it's supposed to work. Loader hydraulics are great, plenty of pressure. Buy the pressure is so weak at the line that feeds the 3pt valve that I can plug the line with my finger
I still think your problem is in the back. That diverter is just a diverter. You've proved that there is flow available. The 3PH should work with the valve in either position.
There's another relief valve in the 3PH body. If it's stuck open, it would give the symptoms you have. And much of the 3PH function is based on dumping fluid off, so if there's something amiss, no pressure developes.
Dumb question - have you confirmed that the lever and linkage actually move the spool?
If you haven't, download the WSM. It's better than I first thought. As with most Kubota WSMs, it's broken into two main sections - the M (mechanism) explains how stuff works and the S (service) tells how to fix it. There's a hydraulic diagram that shows that diverter valve (simple) and the 3PH control (pretty complicated).
That's all I've got. Keep us informed.
North Idaho Wolfman
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Sounds like the issue is in the relief valve.
Have you rebuilt it?
It's in the cylinder head cap.
Have you rebuilt it?
It's in the cylinder head cap.
I have disassembled the 3pt valve completely. Everything looks in tact. Spool moves freely, no blockages, springs in tact. The linage for the lever and feedback rod under the front cover are operating the spool correctly. Confusing part is I don't have any pressure getting to the back end at all. I have been around hydraulics a long time but this is stumping me. Oil delivery to the back is there but even the line that feeds the rear won't build pressure. I removed the feed line on the 3pt valve, ran the tractor and was able to plug that line with my finger. I would think the pump should easily build enough to blow the fluid right past my finger but it doesnt
So I thought the valve in the cylinder head cap was just to adjust the lowering speed and the pressure relief was in the 3pt valve? Plus i cant build pressure in the line that feeds the 3pt valve.Even with nothing hooked on the arms, the only way it lifts is if I loosen the stop on the adjustment and bottom that adjustor out. Even then I can hold the lift arms back by hand
Well, since you can block the pressure line to the back with your FINGER then yeah, stop worrying about the valve, the relief, any of the stuff past that.
As far as the flow divider function for the power steering, i have an inkling that the flow divider might be in place even on tractors that had power steering optional but weren't equipped. My b8200 for example could be had with power steering but mine doesn't have it. If the divider is in place even when those ports are blocked then that would mean you could simply block your PS pressure port to test if the divider was causing your problem. I will try to remember to look at my b8200 to see if the flow divider valve is present when i get home today.
As far as the flow divider function for the power steering, i have an inkling that the flow divider might be in place even on tractors that had power steering optional but weren't equipped. My b8200 for example could be had with power steering but mine doesn't have it. If the divider is in place even when those ports are blocked then that would mean you could simply block your PS pressure port to test if the divider was causing your problem. I will try to remember to look at my b8200 to see if the flow divider valve is present when i get home today.
yes it appears it's only there on PS models. i removed it and tried to take the divider out of the equation, ended up losing all hydraulics and PS, but i did not cap the PS circuit as well, maybe that would identify something.
the part that keeps hanging me up is, the 3PH will HOLD weight...so if i lift my weigh box and allow the piston to rise, the 3Ph will hold the weight box, i have left it up for a week and it never dropped on its own. that tells me the 3PH valve & piston are all sealing/holding properly. if the pressure relief if the 3PH valve was messed up, i would think that would effect its ability to hold weight as well...
maybe the issue is in the divider...or is it possible the pump is weak and has the ability to run the PS and the loader but not the 3PH? im stumped...
North Idaho Wolfman
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No the cylinder cap has the system pressure relief valve in it, not the diverter valve in the front.
You will need to give me the tractors serial # for me to give you the right Cap diagram as there was three different ones used on that model.
if there were an issue with the valve in the cap wouldn't the 3PH drift under a load? it will hold weight for much longer than i would ever expect it to...
Just an unrelated point, but NEVER use you finger to test pressure on a potentially pressurized hydraulic line! NEVER...
yes, i know better...one of those stupid things you do in the back forty out of desperation.
i can get my hands of hyd. test gauges. anyone know what the capped pressure should feeding the 3PH valve?
North Idaho Wolfman
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No it's not the control portion, it's just the pressure regulating portion.
The control portion is on the side, I'm not saying you don't have a problem there.
You will need to pull the cap to see if the poppet is stuck or contaminated.