Replacing seals on cylinder. Cylinder shot?

[joea99]

The saga of replacing seals on Kubota B21 BT721 BH dipper stick cylinder continues.

Today's chapter brings the bitter disappointment of the Rod and Piston getting within a couple inches of the end of the cylinder, just below the fluid elbow and refusing to come out. I have to pound it back in with a dead blow hammer, at which point I can move it and try to pull it out again. Still gets stuck. The WSM shows it coming out easily.

I suppose I could pump air into it, with both ends secured well to, hopefully, not send them to the moon when, if, it breaks loose, but that seems berry berry dangerous.

I find it odd that, on the machine, while pushing the rod in to expel fluid, it went in really easily till there was only an inch or two of shiny left exposed. From there it would not go in any further, I did give it some taps, gentle I thought, to see if any more would come out. Nope.

Wonder if I burred up the piston at that point?

Suggestion to get it out? Just a bigger hammer? A come-along or chain hoist rigged up?

 

[duffer]

Try removing the fluid elbow at that end. It's probably doubtful it's the problem, but you never know and it's a lot easier to remove that, than hook up a come-a-long.

You also might want to try rotating the cylinder as you try to remove it. Maybe the seal is getting caught up on the way out.

 

[joea99]

Try removing the fluid elbow at that end. It's probably doubtful it's the problem, but you never know and it's a lot easier to remove that, than hook up a come-a-long.

You also might want to try rotating the cylinder as you try to remove it. Maybe the seal is getting caught up on the way out.

I did finally get it out. I used a port-a-power that was collecting dust. Put a pipe through the rod pin end and pressed against that. Took about 10 minutes as it tended to cock the rod in the cylinder and I had to move from side to side. Probably need new bushings now.

After I got it to even with the end of the cylinder I used a dead blow hammer to pound it out the rest of the way. Of course, when it came out, the cylinder tilted down from my holding vise and gifted me with more hydraulic fluid on my bench. Lucky I laid down paper.

The cylinder does not look damaged from what I can see so far. No burrs around the hydraulic fitting. Might just be wear in the middle of the cylinder?

I'll take a break from it for a while and figure out how to check the rod straightness without vblocks and such. I may just roll it on a flat table and look for daylight.

 

[ROUSTABOUT]

Clean the end of that cylinder bore. I always stand the barrel on floor and drop rod into it and hold the rod up high and wiggle the junction in a circular motion until piston drops into bore. Then ease it on down. I've done cylinders that had 6" rods and lifted drilling rigs floors. We made the cylinders. I saw good welders that could weld the inside of the cylinders holding a small mirror to see. After the barrel was welded up we would machine a smooth bore and then install. Look up Flex 4 _3 H&P and see what I built.

 

[joea99]

Clean the end of that cylinder bore. I always stand the barrel on floor and drop rod into it and hold the rod up high and wiggle the junction in a circular motion until piston drops into bore. Then ease it on down. I've done cylinders that had 6" rods and lifted drilling rigs floors. We made the cylinders. I saw good welders that could weld the inside of the cylinders holding a small mirror to see. After the barrel was welded up we would machine a smooth bore and then install. Look up Flex 4 _3 H&P and see what I built.

The closed end, open end, or both?

 

[joea99]

So . . . I wiped down the cylinder and examined it with a ebay bore-scope (snake camera).

This is what it looks like:

Not too promising to my very unpracticed eye.

However, I fabricated a "feeler" out of a bit of wood and a finish nail (kinda blunt I guess) and could not feel any "catch" at all.

What do you pro's and semi-pro's think? Do I have a chance at making the team? Or is it time to bite the bullet and get a new cylinder?

 

[joea99]

So . . . I wiped down the cylinder and examined it with a ebay bore-scope (snake camera).

This is what it looks like:

Not too promising to my very unpracticed eye.

However, I fabricated a "feeler" out of a bit of wood and a finish nail (kinda blunt I guess) and could not feel any "catch" at all.

What do you pro's and semi-pro's think? Do I have a chance at making the team? Or is it time to bite the bullet and get a new cylinder?

At this point, is there hope? I suppose just forging ahead and see what happens is worth a try?

 

[LD1]

What made you decide to tear apart the cylinder? What problems/symptoms were you having?

 

[joea99]

What made you decide to tear apart the cylinder? What problems/symptoms were you having?

It was leaking at the rod seal. Not a gusher, but enough to see it running out.

May not matter, but I always felt (bought it used) that it seemed a bit weak when trying to take big bites of admittedly heavy and rocky soil.

 

[LD1]

It was leaking at the rod seal. Not a gusher, but enough to see it running out.

May not matter, but I always felt (bought it used) that it seemed a bit weak when trying to take big bites of admittedly heavy and rocky soil.

Prior to removing you should have done a bypass test to see if the piston seals were leaking.

Too late for that now, seals are cheap so Id rebuild and use if it was working before. Check the rod for straightness or for nicks/scarring. IF its fine it probably only needed new gland seals