Heavy Equipment Repair Questions? Ask an Expert Now.
Sounds like the piston seals on one of the cylinders are leaking. An easy way to determine which one it is, is to raise the boom, loosen the line that goes to the rod end of the cylinder. whichever side leaks is the cylinder that needs resealed.
Sorry, I re-read your request. In your case with the bucket leaking off when rolled up, you would have to loosen the barrel end line (the line toward the top end of the cylinder) with the bucket rolled up. The one that has oil come out steadily as the bucket lowers, is the culprit of the drifting issue.
If you need more assistance, I will be more than happy to help.