Question on hydraulic cylinder repack

[csthompson12]

Hello,

I just got done repacking and installing the 2 loader lift hydraulic cylinders on my 2003 case backhoe...

I did the first cylinder which went well... However the piston and rod assembly went into the cylinder quite hard. Took some fussing around to get it started. Then I had to continue to tap it in with a chunk of wood to continue going in. I don't do these cylinders everyday, so I thought that's just how it goes..

Then I did the second one, and the piston and rod assembly slid right into the cylinder, and I was able to push the rod in quite easily by hand.

I am wondering if I may have messed up the first one when inserting the rod and piston?

Now, I did get the seal kits at different times so they appear to be different brands, could that make the difference? Maybe the wear strips on the piston were thicker on one?

Wondering if anyone has insight, and thought if I should disassembly again?

 

[Ct Farmer]

Two thoughts - one the first one, assuming it was properly lubed and you did not tear a seal ring or something going in and cause it to bind being tight is not bad unless you were beating it with a 20lb sledge.

On the second one , if it just pushed in by hand I’d be concerned that it is too loose and might blow by/leak. If the wear ring is too small the seals aren’t going to last long and worse you risk scoring the bore if the piston rubs on it.

Was it so loose that if you stood it on end with the rod out would it just go in by it’s own weight?

 

[csthompson12]

The one that wasn't so tight may have dropped in on its own, or need just bit of a push. I assembled it horizontally so I didn't test that out.. I would say it felt sort similar to the old seals when I was dissembling it, which I could pull apart by hand fairly easily. I do agree with you that the piston could have been a tad snugger in the bore. The only thing I can figure is difference in the hard wear rings between the kits.. I was thinking the really tight one may be a problem, but now I'm wondering about the not so tight one..

Maybe the aftermarket seal sizes are not as consistent as OEM..

 

[jimg984]

on the one that in hard sounds like it had back pressure, due to still having lines connected to cylinder GL

 

[Swetz]

jimg984 might have hit the nail on the head...I just did a stabilizer cyl., and I had slightly loosened the lines, and it was tight. I took them off and slid right in.

 

[csthompson12]

on the one that in hard sounds like it had back pressure, due to still having lines connected to cylinder GL

That's almost what it seemed like, but in my case I had the cylinder right off the machine..

My problem which made me do the repair was the loader would drift down quite fast.. I'm talking fast, like an inch every few seconds. Also, when I feathered the loader lever to raise the front bucket, the bucket would actually drop. When I pulled the leaver a little more it would start raising. No external leaks though. I thought this was strange and could be a possible loader valve problem.

I tested it out quick with the new seals and that solved the problem. Now it responds right to the lever, and holds in place with no drop.

It seems to work well, so I think i'll go with it. Just seemed strange that one cylinder went together so tight, and the other like butter.

 

[Tinkerer]

It seems to work well, so I think I'll go with it. Just seemed strange that one cylinder went together so tight, and the other like butter.

That is typical of all hydraulic cylinders I have done.
I had a thread not long ago in Shop Talk about a boom cylinder I recently repacked. The piston seals were so tight in the bore I could not get it in the bore. I took it to hydraulic shop.
They told me that they just greased it real good and worked on it till it went in.
Here is a link to the thread if anyone wants to read the whole ordeal.
https://www.heavyequipmentforums.com/threads/purchased-my-last-bulldog-seal-kit.81148/#post-866805

 

[highwayghost]

I did a steering cylinder recently and had to pre-compress the seals with worm gear clamps for several days to allow reassembly.

 

[Welder Dave]

I took the rods for my 4 in 1 bucket to shop to have the piston bolt removed and seals replaced. What I really liked about the Cat cylinders is the bore is tapered at the gland end so the piston fits in easily. The rod could actually stand up in the tube. I put a piece of wood on the rod and gave it couple smacks just so I could get the external threaded gland nut on a few threads. Then I just tightened the gland nut to pull the piston in. Way better than a straight bore and no threads to potentially damage the seals.