Cracked hydraulic cylinder barrel

inane2 · Mar 11, 2019

Hey guys,

Seeking out the advice of the resident TBN'ers here. Picked up a used Kubota excavator in late 17'. 2006 model, 12k lbs unit, great size for here on the farm. I've only got one leak on the machine and it's driving me crazy. At some point, the cylinder for the hydraulic thumb was damaged, probably snagged into something. Looks like the damage was mostly confined to the flow tube that runs along side the barrel (tube). It's been welded before but continues to leak. When I first got it, it leaked enough that you needed to turn to thumb off when you weren't going to use it immediately. I took the cylinder off, cleaned it up, identified the problem area best I could and took it to a friend's shop. He grinded it down and into the area, following the crack. Welded everything up. Hooked the cylinder up and it was much better but still leaked. Removed, more grinding and more welding. Slight improvement but still leaks.

One of the problems is the flow tube is attached to the barrel with two mounting tabs. The upper tab is in the damaged area and it's just a hard area to work with. I don't mind to give it another shot, but was curious if a replacement barrel would be available? The thumb is OEM from Kubota and came on the machine new, so its 13 years old. The whole replacement cylinder from Kubota is well over $1k. I wouldn't mind to replace the barrel, repack the cylinder and call it a day. Who knows, the barrel may be as much as a new cylinder.

The only marking on the cylinder is "GMI 4697 10/03". I googled that and ended up contacting Garrison Manufacturing Inc. They are a cylinder manufacturer but acted completely confused when I called them and advised that what I had did not come from them.

I'll try to upload some pics from my phone. Thanks!

inane2 · Mar 11, 2019

inane2 · Mar 11, 2019

inane2 · Mar 11, 2019

boomer1025 · Mar 11, 2019

Take it to a place that does TIG welding and see if they can clean it up and TIG weld it where it's been welded before.

PILOON · Mar 11, 2019

boomer1025 said:
Take it to a place that does TIG welding and see if they can clean it up and TIG weld it where it's been welded before.

Would be my first choice!

Barring that another possible solution would be to cut the external line and install some sort of suitable fitting and extending the pressure hose to meet that new fitting. Cost would be minimal.

wdchyd · Mar 11, 2019

Real common problem on thumb cylinders as the torque and twist of the hose does damage, the adapter welded on the tubing has no support and may be too thin of wall thickness.

The right fix is to disassemble cylinder, remove the tube assy, save and clean up the female boss tubing adapter, new heavy wall tubing (IIRC the other end has a tight 90 deg bend where welded near the gland head).

TIG weld new tube assy back on, weld other end, then weld 2 reinforcement square blocks (yellow lines in pic) on both sides of tube adapter (1/4 - 5/16” thick).

It’s not worth trying to reweld the old tubing, it will leak again. I have plenty of that tubing in stock if you can’t find any locally.

inane2 · Mar 13, 2019

Thanks guys for all the replies. I was ready to try something else other than more grinding and mig welding.

WDCHYD, thanks for the insight. Funny you mention the torque and twist, that female adapter was so badly bent over, it was almost touching the barrel itself. The pics I've attached are after we straightened it some. I like your suggestion for the repair. Just to be clear, you'd cut the whole tube off and start all over? It does a slight 45 back into the body (barely visible in the 2nd photo at the bottom). I definitely want to add the extra supports near the adapter.

wdchyd · Mar 13, 2019

inane2 said:
Thanks guys for all the replies. I was ready to try something else other than more grinding and mig welding.

WDCHYD, thanks for the insight. Funny you mention the torque and twist, that female adapter was so badly bent over, it was almost touching the barrel itself. The pics I've attached are after we straightened it some. I like your suggestion for the repair. Just to be clear, you'd cut the whole tube off and start all over? It does a slight 45 back into the body (barely visible in the 2nd photo at the bottom). I definitely want to add the extra supports near the adapter.

Yes, replace the whole tube, reuse everything else. Much easier to clean up the adapter fitting and weld it on a bench, then reattach on the barrel. Easy repair, but don’t MIG weld it.

Please give me outside dimension and how long total and I’ll mail you a piece of tubing with a bend in it. You’ll be able to have someone in your area to weld it right. I’ll need your address in a PM.