John Deere – Hitachi 120 With Rebuilt Pump and No Hydraulic Function

[KGB]

We recently had our hydraulic pump fail on our John Deere 120 excavator and replaced it with a rebuilt pump. Currently the machine has no hydraulic functions working with the rebuilt pump.

Prior to the rebuild, pump 1 was functioning and Pump 2 completely failed. This a dual swash plate piston pump HPK055AT Hitachi pump.

I have swapped the Speed Sensing fluid solenoids to see if that was an issue, but no change. I tested the pilot pump pressure and it is around 725psi, so I don't think it is a pilot pump problem.

It seems that this is most likely a faulty rebuild and the swash plates are not actuating, but seems odd that both sides would be stuck.

Has anyone else had a similar issue or have any suggestions?
Thank you.

 

[excavator]

First thing needed is a model and serial number. What failed in the original pump? Was it a complete internal failure? What was your hydraulic system clean up procedure? There are many other questions but this would be a good start.

 

[KGB]

Thanks for the reply; it is a John Deere 120C, SN: FF120CX034513.

The machine ran low on hydraulic oil due to a leak and the pump 2 pistons disintegrated and failed. Hydraulic oil was replaced and all hydraulic filters replaced.

The rebuilt pump was filled with oil and bled, but I am wondering if it is possible that there is air in the cylinders. Seems like tracks should work though.

 

[92U 3406]

If that pump failed as you stated and sent shrapnel through the system then that cleanout is far from adequate. Would not be suprised if there was all kinds of crap stuck inside the main control valve.