Kubota hydraulic issues

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DRShahan
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Zip Code: 20770
Tractors Owned: 1950 Farmall Cub
Kubota B7100 with 1630 loader
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Location: Greenbelt, MD

Kubota hydraulic issues

Postby DRShahan » Sun Dec 04, 2016 9:59 pm

Good evening!
I've got a Kubota B7100 with a 1630 loader that abruptly lost hydraulics a few week ago. One second it was working fine, absolutely nothing the next. No loader function, no 3 point movement, nothing. After tinkering around for a bit (several hours including a fluid change and cleaning the filter), a neighbor revved it to a very high RPM and everything's been fine since. I'm fairly certain that a piece of debris was holding the relief valve open and the higher RPM put out enough flow to open it further and flush it out.

I have also had an odd string of hoses failing this year. 6 total, commonly when I wasn't doing any hard work with the loader. One was while doing a bunch of rototilling when the loader hadn't moved in a couple hours. The hoses are probably pretty old (I've only had it for a couple years), but it's been very well kept indoors and they have very little visible wear.

My question comes back to the relief valve. Although I originally thought that a piece of debris was holding it open until the higher flow dislodged it, I'm wondering if it is gunked up/worn/rusted/etc and just isn't moving freely. If it has also been sticking closed, the higher than normal pressure may be contributing to my hose issues. Is it possible for a relief valve to stick like that on a well running/maintained tractor? If so, would it just be a matter of pulling it and cleaning everything up?

I'm very open to any other explanations. There's a good chance that the hoses are all just reaching their end, but I'd like to track down any gremlins before something bigger than a hose goes!

Thanks!

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Chipmaker
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Re: Kubota hydraulic issues

Postby Chipmaker » Mon Dec 05, 2016 8:07 am

You said you've only had the tractor a couple years. Unless you know who had it personally then you have no idea of how long it sat before you got it or how it was maintained. It is possible if it sat then it could have affected the relief valve, could have gotten moisture in it from condensation etc. If you know where it is it wouldn't hurt to take it apart and look at it at least for peace of mind.
God is good, all the time!
1947 Cub Restoration
1949 Cub Restoration

DRShahan
Posts: 42
Joined: Wed Jan 06, 2016 12:06 pm
Zip Code: 20770
Tractors Owned: 1950 Farmall Cub
Kubota B7100 with 1630 loader
International 2444
Location: Greenbelt, MD

Re: Kubota hydraulic issues

Postby DRShahan » Mon Dec 05, 2016 11:50 am

Any idea whether it would be the relief valve on the loader or the one for the 3pt? I'm not sure whether the loader's relief is functional when those valves are actually in use. It's probably a good idea to clean out both either way.

P.S. nice Cub restoration. I've really enjoyed following that thread.

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Chipmaker
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Re: Kubota hydraulic issues

Postby Chipmaker » Mon Dec 05, 2016 11:59 am

I'm not sure about a Kubota. Haven't been around them, mainly J.D, IH & Ford for me. If I had to guess I would say there's only one pump driving it all since it all stopped at the same time and that relief valve should be for all. Hopefully someone with knowledge of Kubota hydraulics will chime in and help.

Thanks for the comment, glad I was able to share it.
God is good, all the time!
1947 Cub Restoration
1949 Cub Restoration

Jim Becker
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Re: Kubota hydraulic issues

Postby Jim Becker » Mon Dec 05, 2016 3:26 pm

I have no idea how the Kubota hydraulics are set up. It doesn't seem like a relief valve problem. If it is a closed center system, there must be a control valve that needs to function each time the system is used. Maybe that is where the problem is. This would be similar to the orifice screen problem we occasionally see on a Cub.

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BIGHOSS
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Re: Kubota hydraulic issues

Postby BIGHOSS » Mon Dec 05, 2016 4:16 pm

I have no personal experience with Kubota, but the "word on the farm" is their hydraulic hoses have a very short life, especially with the smaller estate type tractors. Don't know of anyone that has solved the problem, except throw new hoses at it. Kubotas apparently are a fine trouble-free tractor, except for this issue.
FYI, my Ford 3000 with a 25 year old Bushog loader still has most of it's original hoses.
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DRShahan
Posts: 42
Joined: Wed Jan 06, 2016 12:06 pm
Zip Code: 20770
Tractors Owned: 1950 Farmall Cub
Kubota B7100 with 1630 loader
International 2444
Location: Greenbelt, MD

Re: Kubota hydraulic issues

Postby DRShahan » Mon Dec 05, 2016 4:34 pm

Jim, it is an open center system. Similar to a bypass block on the cub, there is a block on the side that diverts the flow from the pump to the loader valve. From there a power beyond port runs pressure back to the bypass block to go on to the 3 point (like it would go to the touch control unit). If the loader is in use, the return flow is dumped to tank and there is no power at the 3 point. The intake filter does have problems getting clogged and blocking all flow to the pump, but I cleaned it out (and it really wasn't dirty) and changed the fluid.

Since the B7100 doesn't always have a loader, there is a relief valve near the rear at the 3 point controls. However, there is also a relief valve at the inlet of the loader valve since flow never makes it to the 3 point when the loader is in use. I'm pretty sure this means that the problem must be the loader relief since the 3 point relief is totally removed from the flow when the loader is in use.

Does that make sense? I'm pretty mechanically inclined, but don't have much experience with hydraulics.

Here's the manual for the loader if that helps any, but I didn't find any luck finding a hydraulic schematic.
http://kubotabooks.com/AutoIndex/index. ... =B1630.pdf

DRShahan
Posts: 42
Joined: Wed Jan 06, 2016 12:06 pm
Zip Code: 20770
Tractors Owned: 1950 Farmall Cub
Kubota B7100 with 1630 loader
International 2444
Location: Greenbelt, MD

Re: Kubota hydraulic issues

Postby DRShahan » Mon Dec 05, 2016 4:40 pm

BIGHOSS
That's been the approach so far and will probably continue! This incident is just making me wonder a bit more. My Dad has a larger Kubota that runs at a higher system pressure, most of the rubber has cracked off of those hoses, and even the fittings are about rusted through, but I don't think a hose has ever gone out on it. Maybe it is just a problem with the little ones.

This one is in the 30 year old range, so these hoses might just be at the end.


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