Syleng1
Well-Known Member
Hitachi EX120-2 Excavator
1995 4,500hrs.
I'm having issues with the swing motor. At first it would act lazy after 2-3 hrs. of use and now it barely swings after 10 mins from cold to warm. Meaning it moves left or right but at about a foot per 5 seconds with the bucket and arm curled in. Forget having a load in the bucket or boom extended out. I pulled the swing motor- full disassembly and reseal after no issue found.
At first thought I thought it was hydraulic oil getting hot and dumping back to tank causing me to loose pressure, It was not.
I used a infrared gun to check temps at cooler after 10 mins of running under load.
Not sure which tube is inlet and what is outlet ( to the cooler) but they both are around 130degs F / 54 deg C
Hydraulic Cooler is flowing air easily - if you lightly hold a piece of paper 12" from screen in front of the cooler it sucks it in to the face of the cooler and holds it.
I read some previous posts about a 100-3 overheating and read about a bypass valve for the cooler; I can not find a bypass valve for the cooler anywhere. On the machine or in the book. The oil is fresh and filters are new. Engine is running perfect and no issue with power or engine over heating. After running for the 10 mins the engine temp is 170-180 deg. F. / 79.5 deg C
When run (example- digging rock off the surface of clearing a dirt driveway; for 10 mins dressing up a dirt road on my property) Every dig function on my hydraulic pressure gauge that I screwed into pressure port on main pump per service manual shows approx. 2500psi. Let go of a stick and it drops back to approx. 750psi- 775psi - right where it should. I do not know what high pressure should be. But 2500psi- 2750psi on spikes feels about right.
If you move the joystick to swing- it bounces up to 2500 then drops back to approx. 750psi immediately. If it gets feather it back and forth (neutral / left /neutral left) it will move quicker.
When unit is first started till it hits that magic 10-12min mark, swing is perfect. Both power and speed.
I dont want to disturb the two relieve valves on the swing motor because cold they work find.
I am not getting full line pressure to the swing motor once hot. This tells me there is a relief valve or spool leaking hot, BUT since I am dropping back to pilot pressure (possible psi co-incidence or not?) just after the initial hit of the pilot control ( both left and right) is working, could I have a leaking pilot control joystick?
I have a Russian copy of a service manual I bought on line that was converted to English and I am not super good on hydraulic schematics. Hopefully there is more info out there than what I have.
Thanks!
Joe
1995 4,500hrs.
I'm having issues with the swing motor. At first it would act lazy after 2-3 hrs. of use and now it barely swings after 10 mins from cold to warm. Meaning it moves left or right but at about a foot per 5 seconds with the bucket and arm curled in. Forget having a load in the bucket or boom extended out. I pulled the swing motor- full disassembly and reseal after no issue found.
At first thought I thought it was hydraulic oil getting hot and dumping back to tank causing me to loose pressure, It was not.
I used a infrared gun to check temps at cooler after 10 mins of running under load.
Not sure which tube is inlet and what is outlet ( to the cooler) but they both are around 130degs F / 54 deg C
Hydraulic Cooler is flowing air easily - if you lightly hold a piece of paper 12" from screen in front of the cooler it sucks it in to the face of the cooler and holds it.
I read some previous posts about a 100-3 overheating and read about a bypass valve for the cooler; I can not find a bypass valve for the cooler anywhere. On the machine or in the book. The oil is fresh and filters are new. Engine is running perfect and no issue with power or engine over heating. After running for the 10 mins the engine temp is 170-180 deg. F. / 79.5 deg C
When run (example- digging rock off the surface of clearing a dirt driveway; for 10 mins dressing up a dirt road on my property) Every dig function on my hydraulic pressure gauge that I screwed into pressure port on main pump per service manual shows approx. 2500psi. Let go of a stick and it drops back to approx. 750psi- 775psi - right where it should. I do not know what high pressure should be. But 2500psi- 2750psi on spikes feels about right.
If you move the joystick to swing- it bounces up to 2500 then drops back to approx. 750psi immediately. If it gets feather it back and forth (neutral / left /neutral left) it will move quicker.
When unit is first started till it hits that magic 10-12min mark, swing is perfect. Both power and speed.
I dont want to disturb the two relieve valves on the swing motor because cold they work find.
I am not getting full line pressure to the swing motor once hot. This tells me there is a relief valve or spool leaking hot, BUT since I am dropping back to pilot pressure (possible psi co-incidence or not?) just after the initial hit of the pilot control ( both left and right) is working, could I have a leaking pilot control joystick?
I have a Russian copy of a service manual I bought on line that was converted to English and I am not super good on hydraulic schematics. Hopefully there is more info out there than what I have.
Thanks!
Joe