Kubota questions

[LilBuck]

First off Thanks to Mr. K for getting me squared away and able to post!!! I have numerous Kubota tractors or equipment powered with Kubota engines so very excited on my part to find this forum. My first question is for a 1992 M6950 with 2300 hours and FEL. My hydraulic warning light came on and the loader started acting sluggish. I replaced the 80 filter and within 3 hours of run time same thing happened. When I pulled the filter there was a little milky fluid so I drained all the fluid, 2 sumps, and replaced fluid and filter. Again within 5 hours of operation I was running a 9 ft disc mower and the PTO shot off and front loader was again non functional. Is there an extra filter I am missing or is it possable that there is a sump screen or something check valve etc???? I have pulled the filter and the fluid looks fine now and the fluid level seems to be in normal range. Any ideas would be greatly appreciated.

[Mr. K]

Hey Buck, welcome to the forum, glad to see that you are all fixed up now! Did you have to click the "Remember Me" check box near the username and password entries to be able to post properly - I know some folks on AOL are having a hard time and this fix worked for them, I was wondering if you needed to do the same.

[LilBuck]

Nope I am not an AOL user so what ever you did to activate my account did the trick!!! Thank Again

[Service Dept Vic]

That's very interesting on your wondering about a sump screen, because Kubota does list both a spin on filter and a fine mesh tubular suction screen as being available for the M6950, but I'll be damned if I can find a Service Note that details it's location, or a serial number cutoff.

Have you looked inside the "failed" hydraulic filters to see if they destroyed? The original Kubota hydraulic filters have a fine metal mesh screen, with a magnet centered in the inside of the filter, and they are washable. There is no paper or "folds" inside a Kubota Hydraulic Filter.

The reason I'm asking is I've had occassion to purchase aftermaket NAPA filters, and they do make a Hydraulic filters for Kubota product. The ones I've looked at have pleated paper as the filter media and that just ain't gonna hold up to the suck of a Kubota hydraulic pump!

Did you use a Kubota Hydraulic Filter or an aftermarket filter?

The only place a suction screen would be if your M6950 is equipped with it, and it may not be, is right behind the suction tube banjo fitting.

[LilBuck]

Vic Thanks for taking the time and researching for this!! I used genuine Kubota filters as I cannot find an aftermarket cross for this filter. The filters are just as you say with the wire mesh and magnet and they look good, no deteriation or black junk coming out of the bottom. I washed the first one I replaced with diesel just to see what would come out of it and really pretty clean. I did not realize these were washable filters although I admit to trying that just to get the hay mowing done. What do you recommend washing the filter with?? I will check the return line behind the banjo fitting this weekend as I have a sneaky feeling there is something else going on here!!! Thanks again!! I love this site!!!! Buck

[Service Dept Vic]

Buck, you can wash that out with any solvent, like varsol, kerosene or even diesel fuel.

Kubota hydraulic filters are too expensive to toss out. After cleaning and rinsing a couple of times, make sure to use a good strong Maglite or other powerful pin-point style flashlight, and get a good look inside the filter for any holes in the mesh.

If the magnet is covered in particles wipe it off before spinning the filter back on, and maybe start thinking about whether "power-shifting", uphill pulling a hay wagon with six round bales at 25mph is a good idea!

Fill the filter with fresh oil before spinning it on as your filter "hangs" from the filter housing. For Kubota owners with a hydraulic filter that "stands" on top of the filter housing, fill the filter 1/2 full and quickly get it spun on. You need some oil in the filter to get the pump primed.

You indicated that the hydraulic warning light came on prior to you losing the hydraulics and this is because the hydraulic circuit has a temperature sending unit located at the hydraulic oil filter housing, so it would appear to me as though the hydraulic oil was over heated.

In a hydraulic system the fluid travels around and around the circuit and the only "heat losses" will be from tank, equipment and pipe sufaces.

The fluid circuit is quite short in your M6950, so making a "lap" from the tank through the suction line, into the filter, throught the pump, down the pressure line, into a loader cylinder (or PTO drive) out of a loader cylinder and back into the tank takes only a couple of seconds.

The-long-and-the-short of it is there will be an increase in fluid temperature even if the hydraulic system is "circulating", and doing nothing! The fluid resivoir of your M6950 contains 13 or so gallons of hydraulic oil, and the hydraulic pump on your tractor chimes out approx 25gpm of flow.

Sooooooo, that means when your M6950 is operating that 9' disc mower, the hydraulic pump is completley exchanging the 13 gallons of hydraulic oil in the tractors resivoir "twice" every single minute of tractor operation.

The Laws of Thermodynamics take over and the temperature of the system continues to rise until it is well above ambient, turning on your "Hydraulic Warning Light", after 5 hours of mowing!!!

As the temperature of hydraulic oil increases it's "input" power falls or "fades" out.

If the total loss of power is greater than the heat dissipated, the hydraulic system will eventually overheat. And overheated hydraulic oil loses its lubricating properties, causing increased friction and wear on all hydraulic components, a vicious circle.

Yet another problem caused by high oil temperatures is reduced oil viscosity, which I think explains your loss of "hydraulics". It can also manifest itself as "oil leakages" at cylinder seals, because hydraulic components are constructed with very close tolerances, high heat and lubrication loss can also cause severe damage or seizure to these parts.

I'm starting to think that your problem is due to simple overheating,and if you were to install an aftermarket "transmission style" oil cooler or heat exchanger, if that wouldn't solve your problem.

I've poured over the hydraulic circuit schematic for your tractor and don't see where a suction screen would be, but if you find one and it's plugged with crap, then it's OK to disregard all my blather!!! :cool:

[LilBuck]

Wow Vic this is fun as you have given me some ideas as stuff to do with my tractor that i never even thought of like power shifting uphill with 5 big round bales!!! That really sounds fun but dangerous:) The temp idea is right on the money with that big of a disc mower and the pto will overheat and shut down after about an hour or so, that fixes that problem as i sold that disc mower and went with a smaller 7 foot much beter to run off of a 70 hp tractor. The light comes on right at start up though and stays on the loader might be sluggish right at start up or it might work fine for 10 minutes and then get sluggish. If I drain the filter and put it back on the system seems to prime just fine I let it run for 10 minutes and then the light is off and the loader works fine for any where from 10 minutes to 20 minutes and then light comes on and loader gets sluggish?? Anyway I know I am beating this horse for all it is worth, so I will double check the fliter for debris and the magnet for metal and I appreciate the info on washing these things as as you say 70 bucks for a filter isn't cheap!!! Thanks again for all the patience and hard work!!!! Buck

[Service Dept Vic]

I am mulling over this new information......................