Komatsu SK 820 wont turn/hydraulic problems

[Blazej]

I own a 2004 +/- Komatsu Sk820. The machine runs good and has lots of power to go forward and reverse, loader arms, and buckets movement. However when I try to turn the machine at idle to about half power it seems like the "parking brake" is on. It wants to turn but doesnt. At full power the machine turns but hesitantly. There is a electronic parking brake on the machine however it seems to function as the machine moves forward and reverse, but I dont know if there are other hydraulic solenoids on the machine that are blocking turning or if there is one in the pump itself. I've changed the hydraulic oil/filter and lifted the machine to check for play on the hubs. I have heard that there can be airpockets within the hyraulic system but am not sure of how to purge the system of air. Hopefully its not the drive motors, but I doubt both of them went bad simultaneously but stranger things have happend:shocked:. Any advice would be great before I start tearing into it more.

 

[setxjd]

From what i have read and much like other brands, you can change operating pattern. "Normal" is left joystick controls steering, and right controls bucket? Or optional pattern splits the functions of the joysticks. This is a lever to change patterns, but is an option. what i'm getting to is that if you have this option, i have seen the lever not fully changed over, or sometimes leaking by, basically confusing the hydraulics. Lol. Almost never 2 drive motors at the same time, usually a control problem. This is a closed center load sensing system, supposed to keep hydraulic pressures stable no matter the multiple actions, with variable displacement pumps. As for me, its way beyond my hydraulic knowledge.