I have a problem with retracting rod of the boom cylinder at a new miniexcavator. It's pilot operated spool. I checked everything but the spool itself and the components. When retracting rod into cylinder it is an obstruction as it doesn't let bottom oil from cylinder to go freely back in the return line/tank. After 100 hours , this problem laminated my hidraulic oil and really broke his molecaular structure and turn it brownish dark (Iso VG46) and heats above 80 degrees celsius. Is it posible that somehow the joystick pilot pressure isn't enough to push the spool proper into corect position and the return line is chocked? Maybe the spool spring too stiff? Any help apreciatted. Thanks.
