Kubota M6800 Hydraulic Issues

amschind

New member
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Equipment
Kubota M6800
Sep 30, 2024
3
0
1
Texas
I just got a new to me 1999 M6800 4x4 with just under 400 hours. I had a mechanic local to the tractor pick it up, and he rebuilt the steering and brakes for me before I grabbed it. I have found that the hydraulics are extremely weak and intermittent: power steering kicks in every so often, but rarely, the 3 point arms will raise but only slowly, and the PTO runs intermittently. My neighbor, who is keeping the tractor for me, noted that when he tried to use a wood splitter on it found that it would not power the splitter either. In short, EVERYTHING running on hydraulics exhibited exactly the same behavior consistent with weak and intermittent hydraulic fluid flow. I already had a new hydraulic pump with plans to replace it, so I started by replacing that with no improvement. I called the mechanic, and he indicated that he had replaced all of the fluids and filters EXCEPT for the hydraulic/transmission and those filters, which he had merely topped off. Of note, the fluid on the hydraulic dipstick is so clear that it's hard to even see a level, but I have no idea what lurks at the bottom near the drain plug.

In the process of replacing the hydraulic pump, the teeth on the drive all looked pristine (as did the entire pump), and the feed line from the transmission looks perfect. At the time, I was under the impression that the hydraulic fluid and filters were new (they look brand new), and only learned that they were used after I called the mechanic again. Thus I have some hope that draining and replacing the fluid and filters could remedy the situation.

With that back story, I have three distinct questions:
1) Super UDT2 is not cheap (I learned the hard way last week that Kubota Dealers, like many dealers, charge a premium for their "expertise".....one dealer tried to sell me an entire 3 point arm to replace a missing pin). I am fairly certain that I have a mechanical transmission as the tractor shifts great and the clutch works great while nothing affiliated with hydraulics does. I have seen it suggested on this forum that clean diesel is a good washing agent EXCEPT for hydraulic shuttle transmissions; I would much rather buy cheapo hydraulic fluid as a flush rather than risk harming stuff buried inside the tractor, but I won't really know until I see what comes out of the drain plug. A middle ground might be to buy 11 gallons of hydraulic fluid from Tractor Supply/Scamazon filters and then drain that and replace it with SUDT2 and Kubuta filters.

2) The Kubota hydraulic pump looks awesome and clearly was not the issue save for likely being exposed to fluid starvation. It appears to be a pretty simple device, and I see no reason why I wouldn't rebuild it if kits are available. If anyone has an easy way to track down kits as opposed to complete pumps, I'm interested.

3) I have 1 aux hydraulic block right now, and I want another block so that I can keep a loader hooked up while using a device that needs hydraulics. I'm looking at the parts diagram on Coleman's and trying to cross reference that with eBay because I'd prefer to spend $200 instead of $1100 for the same part, but I also want to avoid buying a valve that I don't need/valve for a slightly different model. I BELIEVE that it's this diagram and that I want 3A111-82540 (see below). I am leery of going back to a Kubota dealer for help as my first experience (see above) was pretty negative.
Coleman's Diagram

Anyway, I'll keep everyone posted so that you can learn from my mistakes. I have little knowledge and a bunch of questions now, so I cannot add much back yet, but hopefully the day comes when I can contribute.