JLG 40 hydraulic cylinder seal

[stone7]

This is from a JLG 40HA, main lift cylinder.
I was just running the engine, and when I
moved the main cylinder up, this happened.

I am starting from zero on this one.

Is this a seal that can be replaced without removing
the entire cylinder?

Is this the "packing" ?

Does the larger diameter piece on the top of the
cylinder case come off, in some way?

Thanks in advance for any information





Does this hex fitting unscrew to remove a pin,
for unfastening the end of the cylinder?




TIA.

 

[harveje]

you may have fixed this already.. I've had to remove and "rebuild" nearly all my cylinders on my 92 40ha and it's a PITA. I did mine by myself and as safe as I could with what I had. Most seals and packing are reasonable online. A few I had to anchor the cylinder end and pull the rod end out with a 4 wheeler to separate them. Of course all the attach pins were frozen and I had to make a few bronze / brass bushings. Now I've got other pump / movement / pressure issues that I'm chasing

 

[stone7]

you may have fixed this already.. Of course all the attach pins were frozen and I had to make a few bronze / brass bushings. Now I've got other pump / movement / pressure issues that I'm chasing

I'm just getting back to this thing. It just started getting warm outside.

Could you tell me about the hex fitting around the end pin? Is that 3/4 inch? Or is it a metric?

I'm going to try to fix the cylinder myself. As soon as I get it un-stuck from the mud.
I just got it retracted today, this is the main lift cylinder, and it would only go up,
I kept trying it and trying it and finally something broke loose. And it spit fluid
and sputtered, but it came down almost all the way.
So at least now I can get in the basket and move it
to a spot where I can work on it.

 

[Delmer]

That part that came out around the rod is the wiper, that's not a problem, you can use a chunk of wood to push it back into place. The oil leaking is from the seal inside the gland (big part at the end of the cylinder that the rod comes out of). You'll need to remove the gland and rod to replace the seal. The cylinder itself can stay in place if it's convenient.

I'd guess the outer part of the gland is a lock ring and will unscrew fairly easily from the inside of the gland which will come out after another retainer is removed, guessing though. If the gland is aluminum, you might be in for some adventure.

 

[stone7]

You'll need to remove the gland and rod to replace the seal. The cylinder itself can stay in place if it's convenient.
I'd guess the outer part of the gland is a lock ring and will unscrew fairly easily from the inside of the gland which will come out after another retainer is removed, guessing though. If the gland is aluminum, you might be in for some adventure.

I did push the wiper back home, and you're exactly correct, the damage is internal.

Using the image, what number #, is the gland?

#3 looks like a big threaded ring. Are you saying this can be unthreaded,
and everything pulled out, fixed, then push it all back in, while the bottom is still hooked on the machine?

(And is the hex fitting on the pin end only a cover?)
(and BTW, do you just use a pipe wrench to remove the ring(#3))

 

[harveje]

The ring #3 / 24 is on there tight--like 4' pipe wrench tight-.. a few of mine I had to leave pinned to the machine, break the nut loose, then remove. The way the assembly is made you will have to remove the nut then pull the whole rod assembly out without messing up the rod (I had to use a 4 wheeler to pull the rod and packing out of a few cylinders). The smaller nut has a small set screw to keep it from backing out. And I think the torque on the small nut is anywhere between 80-600 ft.lbs depending on the cylinder. Take plenty of pictures and somewhere there's some documentation on R&R on these cylinders.

 

[Delmer]

The gland nut is #3, the gland is #4 and the piston is #5. The gland seal is the one that fails first (maybe because the chemistry from the time wasn't up to the task, and the gland seal gets the most environmental exposure).

It will probably be easiest to leave the cylinder base attached, the piston, rod and gland will come out as one piece. And you might have to put the rod back on the machine to bust the nut loose, or pin it to a floor, or dozer drawbar etc. The piston nut will be tight, like 1" socket set testing tight.

The outer nut on the gland #3 shouldn't be that bad, you'll need a big pipe wrench or chain wrench if there's no notches to get ahold of. Or just weld a cobbled up plate wrench to the front of the nut, and as soon as the welds have cooled below 400, turn that nut off. Once the cylinder is back together tight, grind the welds enough to break the plate off and smooth it out. If you use a wrench without welding, first peen that outer nut all around the outside, then heat it up to 200-250F, and then try to break it loose.

 

[stone7]

Thank you, harveje!

Thank you, Delmer!!

It will take me a while to go through these 2 recipes.
Today is moving day. Hopefully.
stby:

 

[harveje]

Absolutely.. I'm still struggling with my aged 40ha but she's as handy as a pocket knife when working.

 

[stone7]

Finally! Out of the mud and at the shop.
I had to move the earth, but it's done.

Now begins the procrastination cycle.
This usually involves at least 1 bender.
Hours and hours of indecision. And more.

First I have to figure out what size that hex thing is,
then order the wrong one, then the right one, etc.
STBY:

 

[harveje]

Well dang I completely missed what hex you were talking about. My apologies. I was referring to the one on the end of the cylinder rod. I’m not sure on that one. Mine has round pins with slots on the ends that metal plated slide in and hold that pin in place. I do know there a pita to remove.

 

[stone7]

...completely missed what hex you were talking about...

Absolutely no problem. I appreciate having someone to commiserate with on this job.

When I took the image on the initial post message, the boom was stuck up high
and the hex fitting looked huge, but when I looked at it today up close, it's only
about a 1/2 inch hex, and I found a hex socket in the garage. So panic attack over.

On the other side, there is, maybe a 1/4", bolt and nut.

So, I still don't quite understand what's exactly going on with this pin.

Either, the hex side, is part of the pin, or it's some sort of cover.
And if it's part of the pin, maybe there are some threads on the pin
to start it out of the hole for removal. That would be lucky.

But then what is the bolt for on the other side.
I'll try to do something on it this weekend.
So STBY:

 

[stone7]

Now I'm stuck a little bit again...

I decided to try and use the "Red Knob" to extend the machine
forward, to more easily work on the machine.
(But it ends up being too high up in the air)

And now I have the tower part bottom cylinder fully extended,
and it seems to be stuck, and it won't retract.

So, does anyone know offhand how to retract the tower to
the home position?

Is one of the limit switches preventing the cylinder from retracting?
I've inserted a diagram to try to explain this. I thought I'd ask
before I start pressing the limit switches randomly.
Anyway, thanks.