That leather hydraulic piston ring

[seanpaintsflames]

I just installed a new gasket kit on my NAA hydraulic system. I had a little hiccup with the leather backup ring on the hyd piston, and I thought I'd share it. I did as much research as the internet would allow before I did it, and seemingly everything I read said to put the leather ring in hot or boiling water for a few minutes to let it soften and it will be easier to stretch on to the piston. Well, I did that, and it didn't work. After just maybe 2 minutes the boiling water shrunk that ring so much that it could fit INSIDE the piston, but certainly not around it. It also didn't really make it more pliable. I tried the heat gun, but that shrunk it even more. Luckily, I had another one.
I've seen solvents stretch rubber before, so I had a brilliant idea for a second. Making do with what I had in front of me, I noticed that the PB Blaster can was tapered at the top, and the can itself was just about the same diameter of the piston. Starting dry, I pushed the leather ring as far down over the can as I could, working it in a circle. Then I squirt some carb cleaner on it and let it sit for a minute. I came back and worked it down some more and squirt more carb cleaner. It was almost over the whole of the can by now, so I pulled it of and worked it over the piston with two flathead screwdrivers; being careful not to gouge the piston or tear the seal.
I learned here that if you try with the rough side of the leather inwards, the smooth side starts to almost crack because it doesn't like stretching. BUT, if you flip it around and put the smooth side on the piston, the rough side stretches right around the piston without an issue. Well, now it was a little too stretched, so, remember that the heat gun shrunk the other one, I put some heat on the seal as it was in the groove on the piston. A couple passes around it and that thing was PERFECT.
Granted, I have yet to fire it up and see if it all works, but the leather ring was the same size as the rubber ring on the piston, and it went into the bore quite nicely. I don't know why the hot water didn't work for me, but I found something that did.

I figure maybe this could help someone else in future internet land!

 

[Soundguy]

you don't 'boil' the ring.

you heat water. then let the ring wet inthe hot water then put it on.

yeah.. boiling hte ring was a no-no.


as for solvents stretching the leather. alcohol is commonly used to size boots .

steam for felt hats.

a couple spoons fromt he dinner tapble will walk the leather rin on pretty easily once lubed with something. oil.. crisco.. vasolene.. etc.

for the N and NAA size you also hav ethe option to use a neophrene ring... easier to work with.. though I almost always used leathers.

at least ya got it on.

pu it on t he corect side right?

 

[seanpaintsflames]

That's funny. I could have sworn that I heard to boil it. Well, either way- I got it on. I got the tractor all back together this morning. All fresh fluids (other than trans) and a new oil filter, new gasket under the leaking hydraulic pump, plus the new pto shaft and lift seals- she works like a charm! It's nice to not drag the bush hog through the yard. Now I've just got to source a cheap exhaust system to fix the triple-leaking one I have now.

Thanks so much for your help!

 

[Soundguy]

best of luck!

ps onthe boiling.. there are quite a few places parts might need a dunk in hot water.. many times stuff gets repeated wrong.

for instance. dipping a shifter boot in hot water ( take off after boiling ).. makes it easier to install.

 

[simonmeridew]

There is an "O" ring available that works in place of the leather ring. I used a new leather ring for years, then the leak started again, so I put the "O" ring in instead, and perfection since.
simonmeridew

 

[Soundguy]

There is an "O" ring available that works in place of the leather ring. I used a new leather ring for years, then the leak started again, so I put the "O" ring in instead, and perfection since.
simonmeridew

i think you are mistaken.

the unit ALWAYS uses an oring. it also uses a backup washer. leather or neophrene are available for most of them.

the backup washer does not have anything to do with the seal.. it's there to prevent the piston land edge from cutting the oring.

if the oring is leaking repeatedly, I suggest you check the cyl bore for scratches. if it is scratched.. you will keep in practice on changing orings. If on the other hand you fix it correctly.. you porobably only have to do it once in your life, and the next owner 50ys from now can do it again.

 

[simonmeridew]

I could well be mistaken, it really has been years since I had the piston out.
Got a leak again.
Got a new o ring and leather ring from yesterdays tractor.
So the leather ring goes over the piston crown first, then the o ring? ...that is, the leather is closest to the piston skirt?
simonmeridew

 

[Soundguy]

open end of piston down on table.. closed end up.

Closed end goes into cyl bore.. open end facesa out for dogbone to ride in.

now.. leather washer on first. then oring.

oil pushes oring into leather washer.. leather washer prevents metal piston ring grove wall/edge from cutting the oring.

so.

Yes.. you are correct.

ps.. hone the bore if it has scratches...

 

[simonmeridew]

It's been probably 25 years since I first tackled the lift piston so my memory isn't entirely clear, but as I am reconstructing what happened then when I took it apart, I think the piston had only the leather ring on it, either from the previous owner just putting that on with no o ring, or perhaps the o ring disintegrating somewhere in the past. I bought the kit and when the leather ring wouldn't easily fit over the piston, I must have figured then that they sent me the wrong thing, and just put the o ring on. It worked for 25 years. My son has the 8N now and I figure I won't be around to fix it again in 25 years so I want to fix it right.
In any event thanks for your detailed help.
simonmeridew

 

[Soundguy]

yep.. the leahter washer is simply a backup ring to help protect the oring.