Guidance on JCB crowd cylinder rebuild (I'm a virgin)

Yes, the small oring goes between the rod and the piston. Unless there's already one there.

The diagram shows 8 pieces in the kit, your pic shows 14 pieces. 5 of those pieces appear to replace the one piece piston seal so that leaves 2 extra pieces in that kit compared to the diagram. The diagram doesn't seem to show the bushing/hard black part that goes in the guide, so maybe 3 extra pieces in your kit (seal kits don't always include those as they don't wear out as fast as the seals) not too bad, right?

Is there any way the fat orange ring goes between the piston and the clip, #14 and #8 in the diagram, that seems to be the only piece you haven't replaced.

Need to get a picture but, I've tried the small o-ring at the base of the threaded rod. Might not be correct....but seems to work there. I imagine it wouldn't get much wear & tear because it's sandwiched between the rod & piston.

The orange gasket... I'm wondering if it could go between the cap and that bearing portion... sort of as a bumper (???)

It will fit there but now there is a small space between the two so they won't be metal on metal.

(I added the arrows to show the section I'm asking about. It would sandwich between those two pieces. It would also not move.

Delmer said:

Is there any way the fat orange ring goes between the piston and the clip, #14 and #8 in the diagram, that seems to be the only piece you haven't replaced.

Click to expand...

I can't swear since this is my first but, if it DOES go in there, I can't figure out how to get it there.

Going at the top (like above post) would also let it serve to help seal the upper portion.

(again, I'm throwing ideas onto the wall)

I'll go get picture to illustrate

Here's what I'm wondering. If I put it between the two as a bumper/seal, there is a gap when the two halves mate up.

Keep in mind.... there is a slight bulge in the end of the cylinder and this is where the bearing resides and the cap is next to it so they don't move during operation.

You can see it WITH the gap (gasket installed) and without the gap (no gasket) and then you can see the gasket.

Delmer said:

Is there any way the fat orange ring goes between the piston and the clip, #14 and #8 in the diagram, that seems to be the only piece you haven't replaced.

Click to expand...

When I look at the original diagram, there are several perspectives on it.

The third one down (showing #8 as the piston) shows a gasket going in the BOTTOM of the piston. I've replaced that one.

Go down to the NEXT diagram and #8 implies that there is a gasket that goes on TOP of the piston which would make some sense to me.

Only thing is.... the orange one won't fit. It's too large and bunches up. It won't come close to fitting in the groove. There IS a bit of a "V" groove there so it's possible something goes there.

This does bring my mind to another idea... the gasket on the BOTTOM of the piston was there (they missed it when they took them all out) I replaced it with it's "mate" in the package.

Could it be that the larger (orange) gasket goes there? Again, it's thicker than the one that's there AND likely to be larger diameter too.... but that's about the only thing that might also cross my mind.

When I said in post #61 that #14 and 8 i was referring to your pdf diagram, on Nige's diagram in post #62 it would be the red circled thing between #10 and 16.

I don't think the orange o ring goes between the cap/gland and the cushion, there is no picture to support that, and it would be squeezed against the moving rod, so it wouldn't last.

I agree, the little o ring is the piston to rod seal.

The lowest diagram (pdf) with piston #8 clearly shows an o ring, the middle diagram clearly shows something larger, that looks like a seal (makes no sense to me) or a larger o ring (possibly a stretch, but makes no sense either in that location).

I say leave the orange ring out for the next project, maybe a cat toy?

Long ago & far away when I was a Jag mechanic, seal kits always had more pieces than necessary. As if some mid life crisis had caused a manufacturing change that took different seals.
Had drawers full of useful useless bits that occasionally did actually fit somewhere.
Joe H

The rest of the story.....

Needed to tighten the piston. Put a lever through the eye end with wife holding ram still. I tightened the piston as much as I could (had some locktite on there too)

Went to install rod into cylinder...

HAHAHAHAHAHAHHAHAHAHA what a joke. I decided after about 45 seconds that I needed help.

Reached out to wife's cousin (lives next door) he and his helper came over.

Took the three of us to get it in. Mounted the cylinder vertically on the ground, put the rod in and couldn't get it to slide in. I'm guessing they have machines for this.

Had two of us hanging onto the rod while a third was using a 3-4 pound hammer to tap the top and SLOWLY drive it in. Got it down to the threads on the cap and finally got those threads started.

Got it back together and nobody broke a finger or had the hammer fall on their head. Carried it (in his loader) out to backhoe and commenced to install it.

Fired it up and put it through some paces.... "so far" all seems perfectly well. I had to hang on the cap screw while mounted to machine to tighten it down further. It wasn't leaking, but I wasn't sure how tight we got it earlier.

So now, it all seems to be working fine. I owe it to you all, thank you!!!!

I think you may have an issue if you needed 3 people and a sledge to get the rod into the cylinder. Some of the more experienced here will chime in hopefully.

I have been repacking cylinders on my machine. It is a Cat 426 and the cylinders are good size. 3.5" cylinder with 2" rod. Weighs 120+lbs. I pulled the piston/rod out by hand and installed it back together by hand. I lubed up the new seals before reassembly. Just a couple light taps to make the eye line up with the hoe bucket. My point being is you may have rolled a seal or dislocated one of the rings.

I knew you could do it!

edgephoto said:

I think you may have an issue if you needed 3 people and a sledge to get the rod into the cylinder. Some of the more experienced here will chime in hopefully.

I have been repacking cylinders on my machine. It is a Cat 426 and the cylinders are good size. 3.5" cylinder with 2" rod. Weighs 120+lbs. I pulled the piston/rod out by hand and installed it back together by hand. I lubed up the new seals before reassembly. Just a couple light taps to make the eye line up with the hoe bucket. My point being is you may have rolled a seal or dislocated one of the rings.

Click to expand...

Being my first, it's certainly possible. Now, (if I have to do it again) it should only take "a while" instead of a week or two.

Question....what would be a sign if I DID roll something?

So far today, it seems to work as expected.

When I held the seal in my hand and put it into the cylinder it was a snug fit. I'm also going to presume I didn't lube things enough. I only lubed the piston and probably should have doused the entire cylinder. That said, I did "pour" a (small) amount of oil directly on the top of the assembly and it seemed to work its way through to the insides.

Still... I was able to hang my entire weight on the rod and it didn't pull it in (about 180 lbs). Then, there were three of us grabbing rod trying to pull it in. Had to get rod about 50% of way in as the cap had been pushed down (when I installed it). Once we got it to backhoe, hooked up hoses and used the hydraulic pressure to retract the rod so it could be properly installed.

Took my outrigger hoses off (sprung a leak) so once those are replaced I'll be able to put it through some paces and work up a sweat.

Just use it as it is. If it becomes an issue, then tackle it.

If it is working then you are successful. Just my experience was different than yours. So far I have done 2 cylinders on my hoe. I plan to do them all. One of two every time I get some free time.

edgephoto said:

I think you may have an issue if you needed 3 people and a sledge to get the rod into the cylinder. Some of the more experienced here will chime in hopefully.

Click to expand...

Considering he’s never done it before so erring on the side of caution, and was only tapping with a 4lb hammer on the rod eye to get the guts into the cylinder I think he should be OK. Plenty of lube is always good.

Nige said:

Plenty of lube is always good.

Click to expand...

That should be the forum mantra!