Ooof… a few weeks ago I sprung a pretty big leak in the tilt cylinder for the loader bucket. Oil was literally pouring out, making it totally unusable. I had just finished making the pad for the new shed and was just doing some cleanup, so I just parked it until I could get to it. Eventually, I had a chance to pull it apart, found an o-ring was obviously destroyed, and ordered a new seal kit that arrived earlier this week. Well, today is “put my backhoe back together” day. Or so I thought… While I was cleaning up the threads on the rod guide I discovered it was cracked between the threads. What the…? How does that even happen? …. and now, I wait for a replacement. Ugh.
I've seen that on a back hoe bucket gland of the same style, at the time I thought it was abuse as the backhoe bucket gets abused normally. You could say a bucket tilt cylinder gets abused to, in this case the linkage should prevent the cylinder from hitting the end of the stroke though. I wonder if it could be internal hydraulic pressure from the failing seal? Does that crack line up with the front corner of the seal groove inside the gland? could be just the stress point, no abuse involved.
It looks like it cracked just about where the gland nut stops. Well before the seal is.
If you have a good machine shop near you, they can weld that up and recut the threads for you. I've had to do it a few times in the past.
Well… after ordering the wrong gland (I blame the parts diagrams) and having to send it back and order the correct one, I finally got the bucket tilt cylinder re-assembled. With freight (both ways) for the wrong gland, plus seals, the new gland, and a bucket of low-viscosity Hy-Gard, this was about a $500 repair. It sucks, but I’m back up and running. So that’s good. But, does anybody know why the gland would have cracked like that? I’d really like to avoid having it happening again. If it was just a freak thing… fine. But if it’s something I did…?
5 threads doesn't seem like enough engagement to be a very strong connection. Was the gland screwed all the way down and the flange contacting the barrel ? Seeing the rust on the gland above the threads leads me to think the gland was not screwed all the way down.
The gland on this cylinder doesn’t screw into the barrel, and there’s no flange on the gland. It slides into the barrel and a lock ring is set into a groove in the barrel that keeps the gland from coming back out. Then, a gland nut screws onto the threads on the gland. The lock ring keeps the gland from coming out, and the nut keeps it from going into the barrel. I don’t see how there would ever be any hydraulic pressure on those gland threads.
When I made my previous comment I forgot you have gland retained by a snap ring. I have resealed that style cylinder, but it has been quite a while since it did it. No hydraulic pressure involved, but a mechanical pressure from the force of the nut. That style gland will have pressure exerted on the threads because it is essentially pulling the gland against the snap ring in the barrel. I wonder what the torque spec. is for that nut. It is weird that the crack developed.
Interestingly enough, there is no torque spec on the gland nut. The manual says to mark the barrel, nut, and gland before disassembly, then reassemble lining up the marks. Not really helpful when replacing any of those components…
That gland is cast iron I assume, and in tension in that portion, and has lots of stress risers at the threads, and is subject to at least indirect shock, so it's not surprising that they will crack sometimes. Any side load from bouncing is transferred to that gland.
Side loading may indeed be a factor. The bucket linkage is definitely a bit sloppy. I’ll look at replacing the bushings and/or pins to tighten it up.