hydraulic leakdown from a hydraulic cylinder

ejensen · Nov 16, 2013

Have noticed that the loader frame on my paulson loader will very slowly move downward when in a raised position. Just found out the structure of the hydraulic one way cylinders used on the paulson I have. Seals are at the top end of the cylinder. No seals at the bottom of the 2 1/4 inch steel shafts which are really the pistons of the steel cylinder. No oil is leaking out the top of the cylinders so I think oil is leaking back through the hydraulic control valve to the reservoir tank. Wanted the opinion of others to see if my reasoning is correct.

Anonymous-0 · Nov 16, 2013

There has to be seals on the piston attached to the cylinder rod. Oil doesn't have to leak out the end. 95% of the time cylinder creep is due to the piston seals in the cylinder leaking.

Bob · Nov 16, 2013

"There has to be seals on the piston attached to the cylinder rod."

NOPE... just a packing gland at the end of the tube.

(NOTE: He said the cylinders are single-acting.)

rufus80 · Nov 16, 2013

There are no piston seals in those lift cylinders. Are made just like original poster stated. Either your valve is not centering correctly or the spools have excess wear and leaking internally.

Bob Bancroft · Nov 16, 2013

You are absolutely correct. With one way cylinders settling under load, if no oil is appearing externally, then the problem has to be in the tractor/valve system somewhere.

Harold Hubbard · Nov 16, 2013

Those are called displacement cylinders. There is a seal at the end around the shaft, and the "piston" is just a guide. When oil is pumped into the cylinder, the rod has to move out to make room for it. The advantage over a sealed piston appears to be simplicity, only one set of packings, and a rod nearly the size of the cylinder, for increased column strength.

Tx Jim · Nov 16, 2013

ejensen
You're correct.Your loader cylinders sound as if they're similar to some combine platform cylinders with no piston or seal. Boom lowering can only be caused from inteernal control valve leakage.

Mike in Mn. · Nov 16, 2013

As stated, there are no piston seals cause there are no pistons, just guides that slide in the tubes. The settling is due to the oil going back through your valve, most of the older style valves do NOT have load checks and will let some oil back through, my old tractors all do it.

Rusty wheel · Nov 16, 2013

I agree with stickweld. There has to be seals on the piston, otherwise the oil would blow by the piston. Should be easy enough to check. Raise bucket and block it up with a hydraulic jack. Plug the return line going to the valve and remove the jack holding the bucket up. If it drifts down, then the oil is going by the pistons. If the cylinders are plumbed together, It could be only one piston is leaking.

Robert Major · Nov 16, 2013

Hi
Some of the single acting cylinders on the U.k Made Horndraulic loaders fitted on 60/70's fords and masseys don't have seals on the rod end just the outer of the cylinder where the rod comes through.
the internal end of the rod just has a steel mushroom shaped head on. first one I ever saw way back when confused the heck out of me. then figured it was displacement cylinder as said. some swathers and haybines have them as the second lift cylinder also I believe.
Regards Robert

Eldo case · Nov 16, 2013

No a ram does not have seals or a piston. Just seals around the rod.

jm. · Nov 16, 2013

Boy Sure can date the real mechanics here on this one. Common sense says there has to be a rod seal. But since there is no rod no seal. Hard for those young boys that have not been there to understand this one. LOL

PJH · Nov 16, 2013

I have an old Farmhand loader with identical cylinders. In that photo of ejensen's tractor, the polished shaft that you see IS the piston. Single acting cylinders, so only one line to them. My cylinders don't even have the guides that others have mentioned. They only have a heavy external snap ring on the end of the cylinder shaft to keep it from shooting out the end of the cylinder tube. The cylinder fills with oil, and the shaft is forced out, even without a "piston" on the end of it. Any problem with the cylinder itself will show as leakage around the shaft. Those cylinders are nice to work on. The head screws on a piece of ordinary pipe. On the head there are 4 bolts thru a plate that compresses the packing around the shaft. You could probably re-pack both cylinders in 30 minutes, without removing them from the loader.

PJH · Nov 16, 2013

A closer pic of the same type cylinder.

ejensen · Nov 16, 2013

Bob,
I also thought there had to be a seal attached to the piston. My concern was that hydraulic oil leaking past the seal would cause a hydraulic lock at some point when trying to lower the bucket. Contacted the company that bought the paulson loader company. I was sent a schematic of the one way cylinder and seals are not attached to the piston.

ejensen · Nov 16, 2013

Rufus80,

Thanks for the information.

ejensen · Nov 16, 2013

Robert,
I have never seen a hydraulic cylinder without seals on the piston. This one apparently has no seals. Including an exploded view of the cylinder sent me from the company that bought the paulson loader company.

ejensen · Nov 16, 2013

Eldo Case,

Thank you for the information. I am curious, where do you get all this knowledge? Have noticed that many people on the forum have a lot of knowledge .
My first tractor was a 1918 fordson. Traded my model A for it. I have worked on tractors for 40 years and have never come across a hydraulic cylinder that has a piston without seals attached to the end of the piston. These hydraulic cylinders were all double acting.

ejensen · Nov 16, 2013

I thought the same as you until I contacted the company that bought the paulson loader company. Person explained to me that cylinders are one way only, I knew this, and that no seals are attached to the piston. Seals only at the upper end of the cylinder.

Tx Jim · Nov 16, 2013

(quoted from post at 16:32:20 11/16/13) Boy Sure can date the real mechanics here on this one. Common sense says there has to be a rod seal. But since there is no rod no seal. Hard for those young boys that have not been there to understand this one. LOL

Yep one could find hen's teeth faster than finding the cyl piston & seals

ejensen · Nov 16, 2013

TX Jim,
Thanks for the support for my thoughts about what is wrong. No oil coming out of the end or either loader cylinder. Control valve at fault.

ejensen · Nov 16, 2013

Yes,
The rod , piston, is 2 1/4 in. in diameter. I like the simplicity of the system. Loader is heavy
but raises quickly .
Have included the schematic of the cylinder sent me.

ejensen · Nov 16, 2013

Bob,
Thanks for confirming my thoughts about what is wrong. Repair should be simplier that rebuilding cylinders.

ejensen · Nov 16, 2013

Mike,
What is occurring with my loader cylinders may be normal if the control valves do not have load checks.
Thank you,

ejensen · Nov 16, 2013

PJH,

Check out the diagram I'm sending. I also thought that there had to be seals on the piston, shaft. Talked with a person in Minnesota whose company bought the Paulson Loader Company and he told me there were no seals on the shaft that is inside the cylinder. Seals at the end of the cylinder only.

ejensen · Nov 16, 2013

TxJim,
You are correct. I have to consider myself in the group with less experience as I thought there had to be a seal attached to the end of the rod, shaft, piston, not sure what is the correct name.I do know that what comes out of the cylinder is 2 1/4 in. in diameter. I was thinking it was very large for the loader. Think I understand now the extra size is for oil to push on the end of the shaft.
Simple design and should be less involved to find out what is leaking in the valve mechanism.

PJH · Nov 16, 2013

That's exactly what I found inside of my cylinders. No guides - just the snap ring to keep the rod from over extending. The V packing is cut - doesn't make a full circle like an "O" ring, and you can place three or so pieces around the shaft, staggering the cuts.

ejensen · Nov 16, 2013

PJH,

Is the rod a tight fit in the cylinder?

PJH · Nov 16, 2013

No - the rod has maybe 1 inch smaller diameter than the ID of the cylinder. The packing at the end fits tight, of course, to prevent oil leakage around the shaft (rod).

ejensen · Nov 17, 2013

Thank you

hydraulic leakdown from a hydraulic cylinder

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