Suffering from the droop

[Changnam 59]

I have a problem with the hydraulic lift on my B6000 in that it will not stay in the up position.

I have a 330 lb tool on the three point hitch. The hydraulic fluid (transmission oil) is clean and of the correct spec.

The lift has always been a little bit droopy in that if I parked the tractor with the tool in the up position it would drop to the ground in about ten minutes. I used it like that for three years.

Now the tool drops to the ground in about five seconds. The onset of this much worse performance was pretty much overnight as opposed to progressive. I have to fix it.

My guess is that the problem is with the lift control valve. I get no results for the control valve part number on either Messick’s website or Coleman’s. There is a secondhand valve on Yenibiz’ website but it is expensive at 600 Euros and I don’t really want to spend that sort of money on a used part that is untested and without warranty.

It appears from the B6000 parts book that Kubota do not intend the control valve to be serviceable although it looks like it can be dismantled.

I have the B6000 service manual and I can see that the system operates at high pressure (85 Bar max.). There are diagrams in the service manual that show how the valve operates but my copy is not clear enough for me to understand it.

I have limited experience with tractors but lots of automotive experience including with hydraulics.

My guess is that there are seals inside the control valve and one or more has failed. But even if that guess is right that does not help much if I cannot source the seals.

I am looking for suggestions as to how to tackle this problem.

Thank you in anticipation.

 

[Changnam 59]

A little more research and I have found some better drawings of the control valve. Drawing does not show any hydraulic seals which seems odd to me.

I have also discovered the actuating piston with O ring which must be another candidate for this fault.

 

[North Idaho Wolfman]

It's not the valve, it's the seal on the lift piston.

p/n 04810-08500

 

[Changnam 59]

OK. Thank you for your reply.

It loos reasonably easy to replace.

I think:

1. Remove cover
2. Push piston out using lift arms
3. Change O ring
4. Reassemble
5. Check operation. Check for oil leaks. Check trans oil level.

 

[Lil Foot]

Correct. If that is the drawing for your machine, it appears to be the same as my B7100. If so, there will be a backup ring in addition to the o-ring on the piston, and a large & small o-ring sealing the cover.

 

[Changnam 59]

I pulled the 3 point lift piston out today and, sure enough, the O ring seal was so worn out that prior to removing it from the piston I thought it was square in cross section.

I ordered the piston O ring and the two others for the piston cover from my local dealer today at a total cost of 3 Dollars for genuine parts.

The B6000 was never officially imported here but the piston arrangement seems to be common with quite a few other models hence the availability of parts in this case.

Thank you, once again, for your advice which enabled me to go straight to what is obviously the source of the problem.