Hitachi EX300-3c pump issue

I've been having problems with the right side pump not working. What would cause main pump to stop working then stop and shut down and it will start to work again. When running machine the bucket will stop and right track wont move and if you shut it down and start it again it will work for awhile again. Could the head of the pump be at fault? Plate separation? How can I diagnose this? Pilot pressure is fine. It has been getting progressively worse also. Thanks for looking and please help if your able.

In my experience it's pretty common on Hitachi pumps. You get some scoring between the seal plate and rotating group where oil pressure can get a foothold and push the two components apart and let the oil just boil in the pump case. The only way I know of to find it is to drain the oil out of the reservoir and then pull the end off the pump. If it is bad it will be obvious.

Why you don't put a gauge on pumps and see the pressure of both track

jey_c said:

Why you don't put a gauge on pumps and see the pressure of both track

Click to expand...

I guess I could check the flow sense, but I believe the regulator is getting correct signal and pump is at fault, but am not sure.

Can I change pump head and plungers instead of removing whole pump? I have another pump that is the same with a different regulator I can take the parts from.

I did one machine years ago where the owner only wanted to replace the brass seal plate. We did and put the machine to work. I never heard from them again so I guess it worked.

Just as an aside, do you have any idea how many operating hours are on the pump and what type of hydraulic oil are you using..?

Well I put a gauge on the front regulator and found that SF pressure has dropped to 200psi from 300psi when malfunction occurs then when you flip key on-off quick it will come back up to 300psi where it should be. I pulled the SB spool out of solenoid valve 1 and found nothing. What would cause this loss of pressure to SF port on main regulator. Also there has been no effect on the rear pump SE pressure stays steady at 300psi. All pressures are neutral control. Also there is no drop in pressure at spool in v/b when actuator is pulled and malfunction occurs. Any ideas?