I am an operator of a Kobelco SK250 that we bought with 3,000 hrs. When we got it the bubket cylinder rod had some scars. About 500 hrs later the chrome plating had started to flake in those areas and if the excavator was parked for a couple weeks you could see oil accumulating in that area. So during winter we took the cylinder to a repair shop where they put in a new rod plus a new seal kit. I used it for a few hrs., then the cylinder started leaking even worse. If the excavator was parked the bucket would start curling up, with the cylinder extending itself out up to 18" in a couple weeks. I also noticed the new rod now had very fine visible scratches that ran vertically every 1/2" around that you couldn't catch with your fingernail, but could sometimes very slightly feel. The repair shop took it again free of charge, found pieces of metal and stone fragments in the cylinder from poor assembly practices, put in a new seal kit, and supposedly polished the rod though I hardly noticed any difference. Tried it out again, and it leaked exactly the same if not worse. I parked it and after 1 day you could already see oil seeping out at the seal area. I am about fed up with those guys. What is possibly wrong? I am not in charge of carrying out major repairs on the excavator but I sure would like to have an idea what's wrong.
If the rod has any marks or rough places it will leak second make sure they are also replacing the head bushing also we have found they do not seem to last long if that is not done also. Also we have had some problems with the aftermarket kits that are out there.
What is the head bushing, where is it located?
Replaceable bushing in the rod gland that the rod slides through, if the bushing is worn it not only causes problems for the seals, the rod can contact the steel of the rod gland causing damage to the chrome on the rod.
Well the repair shop took it back again, so we'll see what they come up with this time.