I am hoping someone can shed a little light on this. I have a 20ton Kobelco and one of the lift cylinders still leaks after being re-sealed but only when not being used. The Kobelco is not getting used much at the moment and fluid seems to be continually weeping and running down the cylinder. The arm cylinder used to do this as well and eventually started leaking while being used, but has not given any problems after being re-sealed, (at the same time as the lift cylinders). The strange thing is, I have just re-sealed the cylinders on my Case 455C and one of the clam cylinders is doing exactly the same thing, even though it wasn't leaking before I re-sealed it. I had to re-seal due to the wipers rotting out and went to great lengths to make sure that the gland head was smooth and free from rust. I recently wiped down the clam cylinder on the Case and tested it under pressure, then left the clam open for 8 hours with the weight of the clam putting pressure on the gland seal: no leaks! 2 days later with the clam closed and no load on the seals, leaking again. I did used a light smear of coppercoat on the gland head just to try and prevent any rusting from water getting past the wiper seal, so I am not sure if that would have any effect. I am keen to hear if anyone else has struck this kind of problem. I am happy to change the seal again, but the only thing worse than doing a job twice, is doing it twice and still having the same result. Baz
What way are you installing the cup seals in the gland? The cup should face the barrel. It sounds like you have rebuilt cylinders befor, and probably know that. It is an easy mistake to make. Also the bushing should be replaced when you repack the cylinders.
Did you hone the barrel or polish the rod?
Sounds like the one i have on a ex220 that was resealed at a hydro shop, I think i have heard of a cause but i cant remember what it was now but like you said pressure or load stops the leak.I know this does'nt help but at least you know its not the only one doing that.Now that i think about it i think it was nicks on the rod or the seal not fitting the groove in the glan tight enough.
The rods are perfect and on the Case were not leaking before. I am pretty anal about fitting seals etc the correct way around and really take my time even though I did 4 cylinders at the same time. I am pretty sure if the gland seals were installed the wrong way around they would leak petty bad under pressure. Although one of the clam cylinders had water get passed the wiper seal in into the gland, the leaking one was the better of the two and never leaked previously. Everything was replaced, the piston packings, the gland bushes, seals, o rings and backups. Bores, pistons, rods, all perfect with no marks at all. I even put the gland in the lathe and polished the inside with wire brush, emery and wet&dry to give it the best chance of not leaking, although I am more suspicious of the fluid getting past the outside of the seal than where it contacts the rod. I used the genuine Case kits that were reasonably priced considering the had ALL the parts needed for the job. The Kobelco also had no problems with marks on the rods and the gland was not imperfect in any way. The Kobelco was a very difficult job to do due to needing some weird specialized piston nut spanner that needed a million ft pounds to get it undone.
Did you use OEM or after market seal kits? I've seen this happen with after market kits, the inner bore of the wiper ring on the gland was just a tiny bit over size allowing it to leak while sitting. When you start to use the machine the seal warms up and expands, stopping the leak. Not to say this won't happen with OEM but I've not seen it.
I used the genuine Case kits that were reasonably priced considering the had ALL the parts needed for the job. I used aftermarket kits for the Kobelco.
Take those machines down to the local dealer and trade them in! You say all the parts are good and you put the seals in right. Then the machines will always leak ,and its time to get new equipment.
This is just the advice I was looking for. Thanks for your help.
Odd shot.. Have you used these machines enough after doing this work? I mean 2 or 3 days of regular full bore usage. Reason: I have had forklift cylinders leak as you say; the customer just had to have it back in use for 2 or 3 days, then I could rework. He calls and say it stopped leaking. Some of the u/cups,poly packs, etc (OEM and after Mkt) are made of such stiff material you have difficulty in getting them on the piston or in a groove. Takes some heat and stress to blow out to fit. Just saying.... Apparently the seals were so stiff as formed they did not "flare" with out pressue. After hot oil and stress, swelled out to fit.
Hey TD24, thanks for the response. I think you make a very good point. In fact I spoke to a mechanic yesterday who I respect more than anyone in the industry and he suggested to give it some more time before pulling it down again as like you mentioned, it will probably stop leaking after a good dose of pressure and heat. The Case has only done around 16 hours since the repair as work is really slow at the moment. The Kobelco has around 800 hrs since the re-seal and I will just live with it leaking while not in use as it is unlikely to improve.
The other thing did you also replace the bushing in the head we have found that if it is not replaced along with the seals a lot of times they will leak again in a short time.
Everything was replaced, the piston packings, the gland bushes, seals, o rings and backups. Bores, pistons, rods, all perfect with no marks at all.