We have a Komatsu 220 LC-8, with supposedly 3000 hours. The main hydraulic valve has developed a moderate to severe hyd fluid leak on the back part of the valve where the In and Out from the main pump oil comes into the circuit valve stack. Under hard steady digging it has built up to a 5 gal leak in 8 hours. Could the pump pressures or reliefs be off?
try to clean the contol valve and check where it leaks, it sounds like an oring below the divider valve that should be changed
Check the flange O-rings, the may be brittle or someone replaced with regular 70 duro when a new hose was fitted.
The o-rings between the merge diveder and the main valve are no good. Needs replacing. Usuaully leaks between the two faces. I have done 2 this year so far. Good luck !