I am currently looking at purchasing a JD 80 excavator. On the machine that I am looking at, the thumb creeps down and when the bucket is rolled up against the thumb it will move about 1/2 way before it pressures up. The thumb opens and closes with when I activate it with the control but quickly creeps closed.The current owner is telling me its just the relief valve. Any thoughts??????
My guess, Bad piston packing. Cylinder needs to be resealed or rebuilt. If this machine doesn't have relief valves that open to tank, you risk literally blowing up a hose or the cylinder tube itself if you roll the bucket hard against the thumb with the piston seals leaking by. It could be something in the valving, but the most likely problem is in the cylinder. Cheers.
Thanks Will check it out when we get it home.