Leaky Seals on 3PH?

drssg · Jan 13, 2020

I have an M5700 that's about 18 years old and has about 1400 hours. I'm seeing some minor and some sporadic issues with the 3PH that are not severe enough to significantly impact the usability, but I'd like avoid having a major problem.

The only consistent thing I'm seeing is that if I shut the tractor down when it's carrying a 3PH implement, it takes about one minute for the implement to sink to the ground. That in itself doesn't bother me, because I don't want to do that. It's just a symptom.

I'm more concerned that sometimes rear implement will rhythmically dip down about an inch or so when it's carrying it with the engine running. I *think* it sometimes affects the power of the FEL, but I'm not sure about that. Sometimes I could swear my FEL used to have more power.

I tried searching for threads with similar issues, and the seals seem to be the most common answer. I have a Workshop Manual and a Parts Manual for the tractor, and they don't seem so definite. The troubleshooting section lists a number of potential causes for this sort of thing.

I've been debating my next steps for a good while. The seal kit for the 3PH pump is about $100, and that would be the most ambitious repair job I've attempted. I'm generally more of a fluids and filters maintenance guy. I could just load it up on the trailer and haul it to the shop. That's not going to break my bank. I just like to fix things myself, if I can. If I felt more confident that the seal kit is the fix, I would feel better about attempting that work.

Any thoughts? I can post relevant sections from the manuals, if anyone wants to see that. They are hard copies, so I'd have to scan or photograph them.

Tx Jim · Jan 14, 2020

IMHO hyd pump is not causing 3 pt hitch to settle but either faulty 3 pt rockshaft piston seal &/or relief valve are at fault or possibly faulty control valve. 3 pt lowering/raising on it's own has in the past been referred to as "hiccuping". The 3 pt rockshaft piston seals in photo appear to be reasonably easy to replace so that's where I'd recommend to start.

drssg · Jan 14, 2020

Thank you very much for your suggestion, Jim. I'm not sure what you are referring to as the rockshaft piston seals. Would you mind referencing the part(s) by number from your diagram?

I also believe I found that same page in my parts manual, in case that helps.

5030 · Jan 14, 2020

I think you need to start with the lowering control valve (knob below the seat) that attaches to a needle valve in the piston body (under the seat), it needs to be able to turn. Closing it keeps the 3 point from dropping, opening it allows the arms to drop quickly or slowly, depending on how far it's open. I bet it's froze up. If it's not, adjust it to control drop. Then you need to see if you have draft or position control because I vet the linkage of way out of adjustment, that causes the 3 point to do what yours does and yes, when the lift arms raise you can feel it in FEL operation

Rarely does the 3 PH piston assembly leak, pretty bulletproof.

You need a shop manual WSM. I think Kubotabooks has the download for your model.

drssg · Jan 15, 2020

5030 said:
I think you need to start with the lowering control valve (knob below the seat) that attaches to a needle valve in the piston body (under the seat), it needs to be able to turn. Closing it keeps the 3 point from dropping, opening it allows the arms to drop quickly or slowly, depending on how far it's open. I bet it's froze up. If it's not, adjust it to control drop. Then you need to see if you have draft or position control because I vet the linkage of way out of adjustment, that causes the 3 point to do what yours does and yes, when the lift arms raise you can feel it in FEL operation

Rarely does the 3 PH piston assembly leak, pretty bulletproof.

You need a shop manual WSM. I think Kubotabooks has the download for your model.

Thank you for the suggestions. I did some tinkering today, and in my case, the lowering control valve is not frozen. Also in my case, changing the setting on that valve didn't seem to impact the issues I see.

While using the tractor today, I noticed that the rear implement was "hiccuping" while the tractor was carrying it. (I like that term. It's quite descriptive of the behavior.) I tried closing the lowering control valve all the way, and it didn't affect the hiccuping.

I then tried lowering the implement. The valve basically did it's job, except the implement slowly sinks down, like it does if I shut off the tractor. I also tried shutting down the tractor with the implement raised and the control valve all the way open or all the way closed, and it behaved the same.

I'm not sure what you mean by checking for draft or position control. The position control seems to work fine, except the for the problems I've described. I don't mess with the draft control lever, and it's always all the way down.

I do have a WSM for the tractor. If I appear uninformed, it's not from a lack of documentation.

5030 · Jan 16, 2020

I have bigger M's but there is a linkage rod between the upper 3 point mount and the and the valving that has to be set properly or the implement will jump up and down. My WSM (as well as my owners manual) explains how to set it.

drssg · Jan 18, 2020

5030 said:
I have bigger M's but there is a linkage rod between the upper 3 point mount and the and the valving that has to be set properly or the implement will jump up and down. My WSM (as well as my owners manual) explains how to set it.

Just to clarify, are we talking about the same sort of jumping up and down? In my case, it slowly sinks down, and then quickly pops back up to the correct height. Each complete cycle takes about one second. I'm not trying to use the implement when this happens. The tractor is just carrying it. It kind of looks to me like the 3PH is leaking down, like it does when the engine is shut off, but the hydraulic pump keeps correcting the height.

My owner's manual doesn't say anything about this linkage. I do have the following section in the WSM: