General Hydraulic Question

mcewan79

Member
Hi Folks

So, I'm repairing the 3 point lift hydraulics in a Massey 202. My question is basic enough that the model doesn't matter (or so I think anyway). Skipping all the painful details and getting to the point. I bought a new cylinder, piston, and rings. When hooked up, hyd fluid leaks from the cylinder. When on the bench and I put air to it, it leaks and air escapes from the cylinder (blowing past the rings). So, I'm 99.9% sure this shouldn't be happening. I could not find anything online about testing the system with air and whether or not the rings would do a good job buffering the air, but I assume so since engine cylinders have rings that do the same.

So, I guess my question is, are my assumptions correct? Any suggestions on what to troubleshoot first?

I was going to mic the components, but I don't really trust my accuracy. The rings were so tight I decided not to bother (ring gap) and groove play, perhaps I'm being too lazy or using too cheap of tools. I mic'd the cylinder and piston and both were pretty much right at 3" as advertised. My measurements showed the piston to be wider, which is why I don't trust my tools nor the operator!

Any help is appreciated. I also have a note into the supplier.


Thanks
Matt
 
They are not a perfect seal. The air will leak a lot more than oil will.

The concern would be something being too tight. Try inserting the piston with no rings. It should slide easily with no binding. Next, insert the rings, one at a time in the cylinder, use the piston to push them in squarely. Then look at the end gap. There must be "some" gap between the ends. Not sure what the specs are, but somewhere around .010" would be acceptable. You definitely don't want them to butt together.

I have put some used cylinders back together that were galled and grooved. They worked fine, just don't expect it to stay up with the engine off, never seen one that would.
 
Thanks Steve, I'll check/add some gap.

I'd like to expand on your statement about the arms not staying up, as that's really my issue here. The arms drop both when turning the tractor off and pushing in the clutch. I don't care about them dropping when the tractor is off. But with the clutch pressed and the arms dropping, its a huge pain. They drop in a matter of seconds, not minutes. So, if for example I have a round bale on the 3 point, in the air, by the time I press the clutch in to shift its on the ground and left behind when I take off. Not ideal.

So I'm tossing this out there in case I have the wrong expectations or something else seems off? I can see a stream coming from the cylinder when hooked back up to the tractor and under pressure. Just doesn't seem right.

But, judging by 1 of the rings I looked at, it may be the gap issue you mention, as the gap seemed non-existent.


Thank you!
 
If you've already got it together, chances are there is enough gap. The gap issue is only if the rings had to be forced into the cylinder. If too tight the cylinder will be scored and ruin the sealing ability of the finish hone. Possibly that happened, let's hope not.

No, it should not drop in a matter of seconds. Creep down, yes, but not drop.
 
I think you are mixing up hydraulic questions with engine piston ring questions ????? at least that's what I'm reading.

If you are working on a hydraulic cylinder oil should not leak out and air should not either. As long as you are within or under the rated pressures. Sure sounds like you have bad seals. There are no end gaps involved with hydraulic seals.
 
Steve

Thanks again. I did get the rings in, seemed fine, but I do know on one that I looked at that there was virtually no gap, so I will recheck this. I've had it back together (and apart several times now). I just assume the leak/stream flowing from the cylinder is not normal. I have not noticed the pressure relief valve to be acting up (no fluid rushing out of it stirring up the pool so to say). I have an extra one on hand and can swap that out easily enough. But I think its more of a cylinder issue.

So, I'll check and add a gap to the rings, and test with fluid vs. air to see if any better.

Thanks again!
 
Mike, these are steel or iron rings, not U cups. My concern was they may have been too big to fit the cylinder without force.
 
So, the end gaps seemed okay, 2 were .008 and the other .0025, and the side gaps were .006. Of course I broke one ring and got the other stuck at the base of the cylinder, so once the replacements come in I will remeasure and reassemble. Still scratching my head on this one. If it continues to leak I'll take a video or something. Appreciate the help!
 
Since it doesn't heat up to combustion temperature and expand like an engine piston, MUCH tighter tolerances could be used.

.006" side clearance seems like a LOT, 'course I don't know what the "fit" was originally.
 
Thanks Bob.

And to be clear in case I did not word it correctly that side clearance is the gap between the side of the ring and the side wall of the piston groove that the ring sits in.
 
Okay, here is my update. I bought a set of new rings (primarily cause I screwed a couple up). Remeasured gaps. The end gaps are .005 - .008, and the side gaps, meaning the space between the side of the ring and the side of the groove in the piston where the ring sits are around .006. So, that seems good unless someone says otherwise.

So, half way put it together while on the lift, added hyd oil and sealed it up. I hung from the arms. I weigh a little under 200. The hyd oil leaked from the cylinder at a rate of about a drop per second. I slapped it back on the tractor and it still leaks like it has before, steady stream. I have a video attached showing the stream and the arms dropping. Finish mower attached for weight.

Again, brand new cylinder, piston, rings. No scoring. Everything seems ship shape. I can see no reason why this leaks. Even though the pressure valve seems perfectly fine, I swapped that too. The issue seems evident, but if anyone thinks something else could be off, please let me know.

Should I try a new cylinder/piston/ring kit, any suggestions? Could I try a different type of rings that could work better?

Video of issue - https://www.youtube.com/watch?v=XtkDntHuBUY
leaking 3pt hyd cylinder
 
Also, I'm using a premium hyd/trans fluid from TSC that meets one of the massey specs (too lazy to walk out and look right now).
Could I try a thicker fluid, or is that asking for trouble?
 

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