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JCB Stabilizer Cylinder Repack

B

BooDaa

New User
Need advice/info on repacking my stabilizer cylinders as I've not come across this type before and not certain the last person who repacked it did it correctly. The piston threads onto the rod and uses squash
point(s) to hold it in place. The cylinder always leaked off slowly for as long as I've owned it and this year it started leaking faster prompting the repack. There is an o-ring between the piston and the rod.
The piston was not tightened all the way to the beveled edge of the rod so o-ring was not compressed. Hoping the photo is clear enough to show the gap between the rod and piston. The o-ring is very fine
(small) so I can't see it withstanding much compression. Any help advising how tightly must the piston be threaded to the rod would be greatly appreciated.
cvphoto33185.jpg
 
I expect AJ will have more and better info for you when he sees this.

The piston should be slightly cut in a taper where the O-ring will be. I believe the piston should be tight to the end of the rod to compress the O-ring into the tapered area. If the O-ring it not compressed it will leak by. You say the piston is held by "squash" points. If those were not made well, the piston may have backed of some over time. Without a service manual or detailed part number info it is hard to say if the last person assembled the sealing components in the right locations. Just my thoughts.
 
every cyl. i have worked on everything is tight DA- tight never worked on a JCB but a lot of Case and everything is DA- tight
 
Thanks. I'm most concerned about the o-ring. It's thin as a penny so fairly certain too much pressure on it would simply crush it and spit it out. The piston is turned from the original squash point and does turn back and forth a small amount.
mvphoto41027.jpg


mvphoto41028.jpg


mvphoto41029.jpg
 
I believe it needs to be tight and "crush" the O-ring into the area between the rod and piston. The O-ring is sealing any imperfections in that joint and won't do that if not compressed in the joint. Wipe some grease on it for lube during tightening.

The external packing on the piston is bad from the looks of your photo. JMHO
 
Thanks very much. I took the piston, gland etc off and it looks like the piston may have been threaded off its seat by close to 3/8 of an inch. I suspect that's why it has always slowly leaked off and now the seals have also failed causing the now not so slow leak.

Here's the inside of the piston and a shot of the gland seals and the seals that came in the kit. Hoping they're going to work.
mvphoto41050.jpg


mvphoto41051.jpg


mvphoto41052.jpg
 
Thought I'd follow up on this and share the findings.

Whoever had previously repacked the seals had placed an o-ring at the end of the threaded rod and the piston. This area is beveled and could be mistaken for a sealing point.

However after searching for several hours I managed to locate my service manual which I had stashed away for safe keeping a few years back.

As can be seen in the photo the o-ring goes on the other end of the threads and gets compressed and trapped there. The piston does not reach the end of the threads nor does it contact the rod at the location the previous repair person placed the o-ring.

Now onto figuring out how to tighten the piston to 300 ft lbs with a gland wrench.

Thanks again for the help everyone.


mvphoto41078.jpg
 

Thanks for the follow up. Goes to show manuals do serve a purpose. That sealing arrangement is different from many cylinders.

You had a couple of the common problems with manuals. 1. Where to put it so it will be safe from damage. 2. Where did I put it?
 
Attention wasn't played by the first guy that repacked the cylinder,he should have noted what fitted where he obviously was not a mechanic,now that you sussed it the nut needs to be tightened,the rod needs to be held solid,I usually use the tilt link position on the hoe bucket to hold the rods I do on site,position the bucket so the tilt link is near the ground,remove the tilt pin,tie the link up out of the way,put the rod in its place,put in the pin,clean block of wood just behind the piston,tighten the piston,if you got a torque wrench that will go to 300 Ft Ib use it,if not a six foot cheater bar and give it one good steady pull and lock it,it will be ok.
AJ
 
Thanks AJ. Being a center mount I had the leg up on blocks so I could make a straight pull on it to get it out. Then just used a saw horse and the pin to hold it in position while snugging it up. Went with a pipe wrench and a 6 foot pipe since the last guy in had already marked it up anyway. Gave it a better squash and some loctite. The backhoe has been in a raised position for several hours now without a hint of movement. Should outlast me. Thanks again everyone.


mvphoto41123.jpg
 
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