Go Bottombroken hydraulics
 | don bailey
Join Date: Posts: 1 
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2002-03-08 36195
I have a small Kubota with broken hydraulics, can anybody give me some clues on what can be wrong before I tear into the whole case. I dont know much about them but I have checked the screen in the case, put a new pump on it and made sure the lines were bleed. The rear hydraulics still do not work. The pump is pumping. Is there some place inside the case under the seat that could be broken or clogged up. I would really like to come out of this with an easy fix instead of tearing half of the tractor apart.
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley 
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2002-03-09 36208
Many tractors have a separate filter for hydraulic oil that should be checked if present. The question is determining if the problem is the pump or the lift. A simple pump test for tractors with loaders is whether the loader still works. Without a loader or other auxiliary hydraulic devices, a test on many tractors can be performed by changing the diverter valve from remote to auxiliary momentarily and listening for the relief valve opening.
If the pump opens the relief valve and the 3ph doesn't lift, then usually the 3ph is at fault and some tear down is required. A common problem is a stuck unload valve.
Obstructed lines will stop hydraulics from working. An obstructed suction line or filter usually starts out with partially working hydraulics that deteriorate after a few minutes. The oil often is over-heated and frothy. Obstructed high pressure lines or excessive loads usually can be identified by an open relief valve at all times the tractor is running.
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| LarryC
Join Date: Jul 2003 Posts: 8 NC
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2002-03-10 36226
The last time I changed my hydraulic oil I could not get the pump to work, I took the top off the pump (where the line exits) cranked the starter, still no pumping.Sooo I held my thumb over the hole in the pump and cranked and Viola! I was covered with oil and my thumb smarted for awhile but the upon reassembly the pump worked. I ssume there was an airlock (or something stopping it from priming) it's worth a try. ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-10 36234
Larry: You might say what kind of Kubota it is so that anybody here that knows the tractor can comment.
Hydraulic oil and diesel fuel under pressure can cause serious injury. It's good to be cautious working on hydraulic and injector pumps. A question to think about is whether the oil would have come out the pump outlet with or without your thumb over the end. What happened could be coincidental.
Low oil or a broken/obstructed line might interfere with a pump's prime, but I think the pumps on most compacts are self-priming. You hear about pumps loosing their primes on old Fords quite a bit, and I think some tractors even have ports on the 3ph for priming the pump. I've heard of people connecting a hose to the pump inlet and running it to a bucket of oil to check for bad suction lines, but it's probably easier to look for symptoms such as hot frothy oil. Drawing oil from a bucket would overfill the sump in a hurry as well. By the same token, if the tractor has a diverter valve, a line could be run from the aux high-pressure port directly to the sump. That would test for high-pressure line and 3ph obstructions. Again, it's probably easier to listen for the relief valve.
At any rate an air locked pump is a pretty good indication that something is wrong, and the suction line and related components is a good place to start. There is an assumption here that replacing the pump would have fixed any problem from the pump itself. Another assumption is that the tractor does not have power steering that is fed by a priority valve.
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 | Murf
Join Date: Dec 1999 Posts: 7249 Toronto Area, Ontario, Canada
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2002-03-11 36255
I would check the 3pth control valve, not the lever, the knob under the front of the seat. When this valve is bottomed right out it completely blocks off all fluid coming out of the lift cylinder, the 3pth will go up, but then is locked there. Check it first. Best of luck. ....
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| LarryC
Join Date: Jul 2003 Posts: 8 NC
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2002-03-19 36492
Tom, I fully realize the implications of the hydraulic oil and pressure I may have dodged a bullet here. The tractor is an L2550 FEL, I've had my share of problems with it (bought used)over the past 3 yrs. I would assume the pump need rebuilding or replaced but as I have the grounds pretty well under control at the new house I seldom use it except for mowing the fields with a bushog. The wife wants a garden this year (groan) so I guess i will appease her, she was reluctant to purchase the tractor but after we moved 1/2 the boulders in NC (seemed like it anyway)she now states "if it flies all to pieces tomorrow we got our money out of it". ....
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| TomG
Join Date: Feb 2002 Posts: 5406 Upper Ottawa Valley
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2002-03-20 36516
I'm assuming the problem is that the 3ph doesn’t lift. Murf's suggestion about the flow control valve is an easy fix if the hitch doesn't lower. That can seem like a problem if the flow control valve was adjusted for a heavy implement that was removed. My own easy fix is to ensure the diverter valve is in the remote position, which will operate the 3ph but not auxiliary equipment such as loaders.
Murf's suggestion about the control valve is another easy fix. The simple version is to move the hitch control lever and verify that the control valve lever actually moves. The hitch and control valve arms are ordinarily connected together by a position control rod, which is adjustable on most tractors. Adjustment should follow procedures in a manual, but position control rods on most tractors can be disconnected from the control valve lever, and the lever can be operated by hand to see if the hitch operates.
These suggestions are easy enough to verify and should be done. If no problem is apparent, I think the first step is to verify if high pressure is being developed in the high-pressure line to the hitch. A pump can be working, but a faulty system relief valve can reduce pressure to almost nothing. Verification of pressure is easy if a loader is present. Otherwise, a pressure test, or causing a relief valve to open with a diverter valve can be done. Note that 3ph’s also have safety relief valves that can be broken and prevent a hitch from lifting.
If the 3ph is getting pressure, Another fairly easy fix is to check the control and poppet valve spools, which are adjustable on many tractors although the lift cover may have to be removed. If the control valve is visible then the ends of both the control and poppet spools can be seen. Operation of the hitch lever should depress one spool in lift position and the other in lower. Neither should be depressed in neutral. Adjustment of the poppet valve clearance isn't too difficult, but a gauge block may be required. It's probably enough to verify that the hitch lever actually depresses and releases the spools. A stuck or open poppet valve will prevent the 3ph from lifting.
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