M7040 3pt hitch drifting constantly

[fast*st]

So the M7040 has this annoying behavior, it settles even while running, with the rear blade on it jumps every four seconds to recover the quarter inch that it settled. While it does this you loose loader control.

Closing the draft valve it sits still and the jerking stops. I'm guessing there's a cut o-ring in the valve assembly, no fluid leaking externally.

Anyone ever dug into the 3pt control valve? quick job?

 

[North Idaho Wolfman]

It can also do this if the piston ring seal is leaking too.

 

[fast*st]

I'd have to look again but I think its two single acting pistons on the back, so it'd have to be leaking externally to sag no?

 

[Tx Jim]

Closing the draft valve it sits still and the jerking stops. I'm guessing there's a cut o-ring in the valve assembly, no fluid leaking externally.

I agree if closing draft control stops jerking then draft control must be the culprit. By stating "closing DVC" you're not referring to the rate of drop screw are you? I presume 3 pt control lever stays where it put IE has tension on friction washers

 

[fast*st]

I agree if closing draft control stops jerking then draft control must be the culprit. By stating "closing DVC" you're not referring to the rate of drop screw are you? I presume 3 pt control lever stays where it put IE has tension on friction washers

Yeah, my err in terminology, drop speed valve halts the constant settling.

Draft and hitch levers work normally though we do have the draft torsion bar unpinned to make it really sensitive for york raking and fine grading.

 

[North Idaho Wolfman]

I'd have to look again but I think its two single acting pistons on the back, so it'd have to be leaking externally to sag no?

Nope, it could be leaking internally and bypassing the piston.

 

[fast*st]

Nope, it could be leaking internally and bypassing the piston.

Hmm, wouldn't that be just the control valve assembly or is there another piston inside? I just see the two big ones outside.

Haven't dug into anything this big.

 

[North Idaho Wolfman]

I'm talking about the piston seals inside the rams.

 

[Tx Jim]

I'm talking about the piston seals inside the rams.

Wolfman
Did you find a seal kit for the lift cylinders? I couldn't find a seal kit. If a 3 pt cylinder is leaking internally where is the oil going? I think the problem is control valve not the cylinders.


To me some Kubota parts are very difficult to locate in parts schematics and I'm no greenhorn at searching for parts. Example is fuel inj pump located under the heading of fuel system? No, it's located under "engine".

 

[GWD]

Maybe something contained in this PDF will help:

Whoops, file is too large to upload.

Go to Messick's http://www.messicks.com/KubotaTractorParts.aspx and fill out the orange box on the left with your tractor's details. Then choose "Hydraulic System" from the drop down list of parts named Section.

The expanded parts diagram will be sent to your email within minutes.

BTW, it does sound like a draft control problem to me.

 

[North Idaho Wolfman]

Wolfman
Did you find a seal kit for the lift cylinders? I couldn't find a seal kit. If a 3 pt cylinder is leaking internally where is the oil going? I think the problem is control valve not the cylinders.


To me some Kubota parts are very difficult to locate in parts schematics and I'm no greenhorn at searching for parts. Example is fuel inj pump located under the heading of fuel system? No, it's located under "engine".

Those cylinders look like they are welded and therefore they don't offer a rebuild kit.
When a cylinder leaks on the piston seal it just sends the fluid from one side of the cylinder to the other, so there is no external fluid leak visible.

I'll agree the draft control would be a more common failure point.
The way the cylinders are setup on the rockshaft it would mean both would have to be leaking, Very slim chance of that happening.

 

[Tx Jim]

Some one way(single acting) cylinders don't have a piston but utilize the rod as the piston. One example of cylinders without pistons is JD combine platform cylinders. Most one way cylinders I've seen with a piston have a breather on opposite end of barrel from hose connection.

 

[North Idaho Wolfman]

These cylinders have a captured venting system so it would be really easy to check them for a bypass leak just pull of the vent tubes if there is fluid there is a problem.

Looking over all the valves it's very likely that it could be a valve causing all the problems.
One thing I noted by looking at the diagrams is that there is a lock for the three point, I wonder if that valve is in the middle of it's operation would that effect the three point?

I was wrong again they are serviceable cylinders just had to stop and read the manual.

I have a zipped full color service manual if anyone needs it, just PM me contact info and I'll send it to you.

 

[Tx Jim]

Thanks for cylinder clarification. Do you have any idea where the cylinder repair kit is in parts catalog? I don't need a kit just trying to understand/navigate Kubota's parts catalog.

 

[Gundoctor]

Draft and hitch levers work normally though we do have the draft torsion bar unpinned to make it really sensitive for york raking and fine grading.

Put this pin back in!!!!

 

[Tx Jim]

Draft and hitch levers work normally though we do have the draft torsion bar unpinned to make it really sensitive for york raking and fine grading.

Put this pin back in!!!!

I missed that OP had the "draft torsion bar unpinned"!! I agree that pin should be replaced and think for fine grading draft control should be set at ZERO

 

[North Idaho Wolfman]

After an extensive search, I can not find a rebuild kit for those cylinders???
Might try a Kubota dealer and see what they say.

 

[Tx Jim]

Thanks for looking but I'll bet it's "hide somewhere" in the parts catalog.