Ex120-2 slow hydraulics

[Syleng1]

Hitachi EX120-2 4500hrs.
I tried to search this but my results were minimal and not relevant.
I’ve had this machine 1.5 years and bought it whooped. Engines runs great and no smoke. Plenty of power but Hudraulics are leaking and pins and bushings are sloppy from previous owners lack of maintance / abuse. Currently the engine revs up and acts normal- no fuel issues.
My issue is I was running for about 4 hours no issues moving rocks and dirt. Almost finished for the day, when to scrape some dirt then I had very little hydraulic power- very slow like it was only running on small pump not big one. Diagnoses shows temp of hydraulic oil was 200+ degrees. I’m thinking I melted the o- rings on the main pump control Solenoid valves.

Funny side effect is after the machine sat for 2 days to properly cool the oil, I fired it up and even in the setting for higher speed, the engine revs up but still slow power- BUT the engine goes to an idle after 20secs of no movement in controls- like it’s idling down to save fuel. Hit a control lever OR track movement and it cranks back up to desired speed. It has never done that since I’ve owned it.

I’m thinking the pump is being commanded to full “on” due to cylinder seals internally leaking and possible valve body leakage. Over heated the oil and melted the main pump control solenoids or at least their seals.
Any help is appreciated. Thank you,
Joe

 

[mg2361]

Fuses good? Do you have 24 V to the displacement solenoids on top of the pumps with the key on? If so, try swapping the solenoid valve assemblies on top of the hydraulic pump (don't move the wires with the solenoids). Report how it operates after doing so.

Do you have DR ZX or DR EX software?

BUT the engine goes to an idle after 20secs of no movement in controls-

There is a button (picture of a crankcase) just above and to the left of the button marked "M". if that button has been pressed then the auto idle is turned on.

 

[Syleng1]

Thanks for the reply.
I will physically swap around the solenoids this week and try. I had planned that before I buy new from dealer - JD. As I’ve heard the eBay units are not good quality. I was wondering if I completely lost main pump drive (rubber drive bushing- flywheel for engine to pump) and the unit runs on the pilot pump but after I realized both pumps run off the same drive. So that a “non issue”

also thanks for the info on the button. I may have pushed that button playing around with trying to get the machine to move. I know it’s something simple, I just need to find it. I have a copy of the service and parts manuals but no computer software or connector to plug in. Till this point in order to fix I’ve followed the trouble trees in the FSM to repair issues in the past. I’m hoping I did not melt down the harness. My goal was to take the machine off line this winter and reseal all the pistons as I know the fluid getting hot is from internal leaking. I’ve been tackling an item at a time to get this ole girl back in proper shape. It’s used about 4 hrs every other weekend on my small farm on CT. Not a daily machine for work. The previous owner used it to crush cars at a junk yard.... allergic to grease sadly.
Look forward to others input as well.
Joe

 

[Syleng1]

So I marked the harness and connectors and solenoids with paint and swapped the solenoids and the machine ran good again. I looked for melted rubber seals. I’m not sure but is it possible they don’t need replacement? I’m going to run it for a bit - hot as blazes here in CT. So it will heat up quickly and retest. Parts of me wants to just order new solenoids from dealer. Big money. I will wait and check. My other thought is the wires from the harness side of the connection are showing copper strand wires. It may be a connection issue at the plug. The plug is hot and went “open.” Okay- off to dig.

 

[majestic]

I have a 120-2 and had a very slow boom. It would slightly speed up with other hydraulics engaged...after removal and cleaning of solenoid no change...unplugged the wires and it worked perfectly.... update, had a similar problem with the tracks, very very slow.... unplugged appropriate solenoid and works perfectly in mid speed. Hope this helps!