re-sealing some old Kubota B8200 FEL cylinders

[dfkrug]

I agreed to fix the leaks on a friend's old 80s era Kubota B8200.

This tractor is common around here, and the way the cylinder goes together is just about my least favorite. The end cap (gland) uses a springy wire that is captured by a groove inside the lip of the cylinder barrel.

I have done this type before, but I am not an "expert". Probably only rebuilt 25-30 cylinders in my life.

 

[dfkrug]

The wire is always stuck in there, so the first thing to do it to free up the gland by pushing it in just a bit.

I use 2 small pieces of steel (A) that will act on the gland, but stay inside the inner diameter of the cylinder barrel. Then I whack gently at B.

 

[dfkrug]

Once the springy wire is freed up, how do you get it out? I am not able get a small screwdriver or any of my dental-style picking tools underneath the wire.

So, I drilled a little hole and pushed it out. Anyone else have a solution they have used?

 

[dfkrug]

And here is the cap and piston, disassembled. I used the rod like a dent-puller to pound them out.

A lot of the goo seems to be grease used in the last assembly.

 

[dfkrug]

Next, I remove the piston nut.

Since it takes at least 300 ft-lbs of torque, I stick a rod in the cross-tube, park the tractor on it, then use a long breaker bar.

 

[dfkrug]

Here is the gland.

Only the wiper (A) and the gland seal (B) needed replacement. The rub-ring (C) seems to be metal, made of plain bearing type material.

Kubota actually still sells a seal kit for this cylinder, but it is listed at $175, or about $200 with tax and shipping! Crazy.

So I just bought A and B, plus the piston seal for $25/cylinder from Hercules.

 

[dfkrug]

In my experience, getting the new gland seal in is very tough if you don't buy the Special Tool. 25mm rods are much more difficult than even 30mm rods.

I recommend this tool.

For the piston seal, I like to heat it and the piston in hot water before sliding it on. I then clamp it overnight with a hose clamp to assist in assembly.

 

[dfkrug]

For contrast, this is a cylinder rebuild on a modern cylinder. This one is off my Chinese 1-ton excavator. The rod was dinged in shipping, so the gland seal started leaking after about 50hr of use.

At the time this happened, I had a spare cylinder, so I swapped it out, putting the leaker on the shelf for later.

This one has a screw-on threaded piston, with its own seal underneath. That sure seems unnecessary.

Thread-locker was also used, so unscrewing the piston was difficult, requiring a giant adjustable wrench and cheater pipe. Prob needed 500ft-lbs.

 

[dfkrug]

Oh yeah, the best thing about the seal on my Xiniu excavator: the maker was kind enough to stamp the size right on the side, and I was able to buy one, plus a spare for less than $10, total cost, shipped from China.