220 pump disengages and re-engages

[stoepgravel]

My hitachi ex 220lc-3 has been acting up lately. When you first start it up, the main pump seems like it gets bogged way down and then kicks off. You let off the controls and it starts working again. If you move really slow, its just kind of jumpy or spongy feeling. I changed the high speed solenoids on the pump and checked the pilot pump filter. It has 15k hours already. What's wrong with this? is it time for a new excavator?

 

[John C.]

My guess is the pump is worn out. I don't know for sure which pump you have but tandem sets would get damage or wear between the piston and barrel assembly and the seal plate which would let oil blow out into the pump casing instead of the into the hydraulic circuit. It happened at moderately high flow and things would stop. Let go of the controls and the seal plate would sit back in place until you powered up again.

On the inline pumps I saw the swash plate control linkages get worn and sticky. At any rate a removal and tear down is likely in order unless someone comes up with something else.