Not sure what's going on here , machine was running great loading some brush in a dump trailer when the boom would not lower after dumping a grapple load of brush. Shut machine down , re started all functions seemed to work except boom down. Shut unit down again and re started after 5 min. Boom lowered all functions were working except grapple arms no longer responded to close they stayed open. After a few min of trying to diag this condition got a warning of hydraulic temp getting hot. (It was idling) Shut unit off. Fast forward a week later machine would not start , battery full but acted weak, used jumper cables (double ought welding lead wire) it cranked over good but now fire. Used gas rag and got it to start but was sluggish starting. Loaded up on trailer to bring home. (Decided id let it idle on way home about 20 min drive) after a few min alarm went off high hydraulic temp so Shut unit off. Been sitting a few weeks here now have time to try and figure out what's going on. Since it been sitting here the grapple arms have both bled down to closed position. As soon as I got in the cab and typed in code to start , I turned the start/stop lever and while cranking the arms rose up , it fired right up then stalled when arms reached open position. W t h .....
This is electrical, not mechanical hydraulic failure. Your aux hydraulic circuit is energized/pressurized continuously and that is causing multiple cascading failures. Aux circuit constantly powered = continuous flow to grapple and your pump continuously working against closed grapple, generating heat with no cooling airflow Aux enable switch or wiring shorted: Keeps solenoid energized even when off. check switch on joystick and wiring harness for shorts/damage. Aux solenoid valve stuck mechanically: Spool jammed open from contamination. solenoid can't close it even when de-energized. ECM thinks aux should be on, continuously powers solenoid
I Have had same problem on a T870 It was contamination in the solenoid (which actuates the spool on main aux valve)
Happy that i am pointing in the right direction. @polarisbryan look for the same
Sounds like an electrical problem is keeping your aux hydraulics powered on. I had a similar thing once, and it turned out to be a bad solenoid on the main valve block that got stuck. Maybe that's a good place to start checking. Good luck, hope you get it sorted out.