Hi everyone I am new to the forum and this is my first post. I have a 2013 Komatsu PC88MR-8 excavator with about 6450 hrs. I am having a problem with the auxiliary hydraulics that power the hydraulic thumb. The thumb does not work until the hydraulics have sufficiently warmed up. depending on them temp this can take anywhere from 20 mins to over an hour of working before the thumb functions. I am in South Carolina so it does not get very cold. I think it is the auxiliary valve in the control valve sticking. When it fist starts working it moves very slowly and then it frees up after opening and closing it a few times. If I turn the machine off the the thumb will take a few mins for it to start working again. If the machine cools down fully it takes longer to start working. I have only put on about 150 hrs since I got the machine. I have changed the hydraulic fluid and filters twice on it since I have had it with the hope of flushing out the system. I also cleaned out the suction screen that goes to the hydraulic pump. The original fluid that was in the machine when i got it was dirty but not terrible, not milky in any way. There was some very fine metal in the bottom of the hydraulic tank when i first changed it but no big chunks or shavings. The only filter I have not changed on it is the one for the breaker. If i understand it correctly the breaker filter is only used if a breaker attachment is installed and used but i could be wrong. There is a an attachment selector valve that you manually have to turn on top of the control valve to get two way hydraulic flow to the aux hydraulics. That is turned to the correct position. Any thoughts on what could be causing this? The machine works well enough for me to use it is just annoying because i have to park it with the thumb in the position i want to use it in next. Are there any additives that can be put in the hydraulic tank to help with this or does the control valve need to be opened up? I am pretty mechanically inclined but I have never taken a hydraulic valve apart before. Any help would be appreciated. Thanks Will
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