I have a 1997 Hitachi EX120-5 Mfg No: IE4-01055 We just replaced the oil seal and sleeve on the swing device, and several o-rings. Now the machine is not swinging in either direction. You can hear the valve opening and closing when you try to rotate it but it will not move. All other hydraulics are working fine.
Swing break disengaging?
That is what we are trying to troubleshoot but really don't know how.
Can you post some pics of the swing motor showing the hydraulic lines and where they are hooked up? also you said you replaced seals and orings... did you separate the swing motor from the swing gear drive? or just do the bottom seals?