Three point hitch slow leak down and hiccups when in use

[Stewartkyle44]

Hello all. I am looking for some answers to where my leak may be coming from. My three point hitch leaks down when not in operation and when it’s in operation it hiccups. The only noticeable external leak I can see is where the PTO shifter shaft from 540/1000 goes into the rear pto housing but it is a small minimal leak and I didn’t think it would be loosing that much pressure to cause the full leak down of three point hitch when tractor is off in about 10 minutes. Was curious if I should start there or is it most likely an internal leak up at the rocker arm shaft. Any help would be appreciated.

 

[TractorTech]

Welcome to TBN. The internal 3pt piston seal is leaking by. Most likely and hopefully, it will just require replacing the oring and backup ring on the piston.
The external leak doesn't have any connection to the 3pt.

 

[Stewartkyle44]

Thank you for the quick response. I attached another picture of a parts diagram to just confirm you are talking about part #8 and #20 correct? Where would the oil be going to if it was seeping past the piston when lifted, just back into the transmission housing?

 

[TractorTech]

Yes, those are the parts. Only other thing that might be wrong, but usually not on a low houred machine, is that the cylinder has some scoring.
The oil leaks by back to the sump/transmission

 

[Stewartkyle44]

The tractor has 1900 hours on so hopefully I don’t have to replace the piston but if I do it’s not too expensive at around a 100 dollars. My concern is I have a DK55c (cab model) and if it really requires removing the cab to get to the upper housing off and access to the piston and seals?

 

[TractorTech]

The piston isn't the problem, even scored, it doesn't affect the sealing. The cylinder #1 would be scored. The scoring, if minor, can be taken out with a hone.

I believe, but can't really tell, that the cylinder can be accessed inside the cab by taking an access plate out or the seat assembly out.

 

[Stewartkyle44]

Okay thank you. One last questions, any tips/tricks or special tools to change the o ring or backup ring?

 

[rScotty]

Okay thank you. One last questions, any tips/tricks or special tools to change the o ring or backup ring?

The other place the 3pt hitch arms can leak down is via the needle valve that traditionally is under the front of the tractor seat. That needle valve regulates the speed that the arms can fall or if turned all the way in it lhydrauically ocks the 3pt arms in whatever position they are in - if there is no leakage in the piston O ring itself.
So you can use that valve to see if you need to replace the O rings in the piston. That needle valve also has tiny O rings, and it dumps the fluid into the same internal sump as the rest of te 3pt system.
rScotty

 

[TractorTech]

Once you have the piston out, just a pick or small blade flat screw driver to remove. Since they are probably the cause, a knife to cut them out and a very careful stretching of the new rings onto the piston.

 

[Stewartkyle44]

Awesome thank you very much for the support and quick responses!

 

[rScotty]

Use the 3pt arm lock under the front of the seat to see if you even need to take the piston out.

 

[Stewartkyle44]

Even with the knob turned all the way to the lock position the 3pt hitch still leaks down. It leaks quite a bit slower but still leaks down. I did notice the hydraulic filter housing is leaking a little at one of the o rings. Could that possibly have anything to do with the 3pt hitch leaking down or is that system closed off or separate from 3pt hitch by a valve or something?

 

[TractorTech]

The filter is on the suction side of the pump and would not affect the 3pt.

 

[rScotty]

Even with the knob turned all the way to the lock position the 3pt hitch still leaks down. It leaks quite a bit slower but still leaks down. I did notice the hydraulic filter housing is leaking a little at one of the o rings. Could that possibly have anything to do with the 3pt hitch leaking down or is that system closed off or separate from 3pt hitch by a valve or something?

The valve does two things. One is it regulates the rate the implement drops when the 3pt control lever is pushed forward. The other is that when it is turned all the way in clockwise it blocks off that path entirely and the arms stay up no matter what you do with the 3pt lever.

So if you had closed the valve and the arms stayed up we we would have known the problem was in the path involving the valve and the 3pt control....not the piston. But since it still leaks down it could be either one - or both. I'm betting it is both.
And because closing the valve did slow the leak a little, that tells you it needs attention. I would probably rebuild that valve first. It is simpler to do & usually just involves taking out the valve assembly apart and replacing a couple of O rings, some packing, and cleaning up the orfice.
If you are real careful taking it apart a good cleaning will be all it needs to get dirt & rust out.

It wouldn't surprise me if you still will need to fix a problem in he piston seal to the cylinder - Tractor Tech has already given you some good info on that. Lots of time a leaky 3pt is traceable back to rust in the 3pt cylinder which eats up the piston O rigs and clogs up the drop rate needle valve.

As for the leaky filter, that is on the suction side. It doesn't directly affect the 3pt arms dropping. When the tractor is running is when a suction leak can suck air into the hydraullic fluid. Air in the fluid will make the fluid look cloudy or murky until the micro bubbles go away - usually takes overnight.
Suction leaks don't leak much oil to the outside when running, and small suction leaks don't cause the tractor to operate much different. That is what makes them hard to find. You find them as a small oil leak or more likely as a wet oily connection when the engine is off.

rScotty

 

[Stewartkyle44]

Thank you @TractorTech, I was really hoping I was not going to have to pull that piston out because with the cab it looks like it’s going to be a long knuckle busting weekend for $32 in parts. Thanks again!

 

[Stewartkyle44]

@rScotty thanks for that info. I know the valve assembly is pretty easily accessible cause I had the seat off today, sheet metal cover removed, and could see the whole valve assembly. While I have it apart I might as well clean that up and change those seals as well. I am hoping I don’t see any rust in the cylinder so I don’t have to replace that as well but that is good info for me to look out for when inspecting everything.

 

[Stewartkyle44]

@rScotty Well looking at the MLS valve assembly group, that looks like a whole new can of worms. Not what I thought I saw today when I removed the seat and cover. That looks to be inside the hydraulic cylinder body. They have a seal kit for $72 dollars otherwise I wouldn’t know where to start with that complicated looking valve assembly haha. I wanted to get all the stuff ordered cause I am out in the country and it always takes several days to a week to get parts delivered before I dig too deep into taking things apart and had everything sitting in my non fully enclosed barn where it gets quite dusty on windy days.

 

[rScotty]

@rScotty Well looking at the MLS valve assembly group, that looks like a whole new can of worms. Not what I thought I saw today when I removed the seat and cover. That looks to be inside the hydraulic cylinder body. They have a seal kit for $72 dollars otherwise I wouldn’t know where to start with that complicated looking valve assembly haha. I wanted to get all the stuff ordered cause I am out in the country and it always takes several days to a week to get parts delivered before I dig too deep into taking things apart and had everything sitting in my non fully enclosed barn where it gets quite dusty on windy days.

Let me attach some beautiful old Yanmar illustrations on their 3pt. from 50 years ago. It will give you a better idea of how the sytem works. Every part will be different of course, but still nobody has bettered Ferguson's original 3pt and they all work basically the same.

 

[Stewartkyle44]

Wow those are probably the best illustrations I have ever seen for anything I have owned. So the stop valve pretty much hydro locks the 3pt when in any up position and like you mentioned it can only leak down from either there or past the piston. The only other way I see it loosing pressure from the illustrations is from the hydraulic pressure outlet. Maybe I should check that as well…if the stop valve is working properly that would not happen though. I appreciate you sending those illustrations over that really helps me understand the flow and how a 3pt moves the fluid around

 

[rScotty]

Yes, mechanical drawing used to be a required course for mechanical designers. At one time all designers could make a creditable drawing. Of course some were better at it than others. Yanmar hired real artists. That first drawing is museum quality in my eyes. Tremendous detail and done by someone who understood how it worked.

The old US series of Yanmars were trying to emulate John Deere's excellent manuals back 50 years ago. I'd say they succeeded.

Not shown is the filter you mentioned. It is in series between the "strainer" and the "geared pump".

rScotty