Hi All, I've got a pc490 on 13000 hours, seems to have been serviced regularly according to the screen. It is very underpowered on the boom lift, and won't lift much more than about 8T with dipper vertical. Some other circuits are a bit underpowered but it is mainly boom lift. There is a bypass in the bucket circuit (bucket drops when curled fully in) which I haven't got into yet but is worth noting. There is another bypass from bucket to Slew in that when you hold bucket all the way in, it'll Slew to the left. Not sure if there is another bypass with the boom lift so worth mentioning. I haven't checked very much yet as I wanted to know if anyone has come across this before before I get into it. Thanks!
Might be good to post a serial number for an exact description of machine. Maybe Lachau will read and comment. He has more experience with the Komatsu brand. Simon C
No problem, serial number K60033. Komatsu PC490LC-10
If you're bucket is dropping back the cylinder is most likely bypassing inside and this would be the first thing to fix
Would not be too hard to disconnect the hose at the opposite end of either cylinder with the cylinder fully extended and put a little force on the packing to see how much oil is bypassing. If your machine has actual 13000 hours on it, it could be over due for more than one cylinder. Don't know the history, and even if relatively new repairs were done , does not mean something could not of failed again. If you're not sure how just ask. Simon C
There's also a hydraulic control unit behind the seat part no 7835-50-3005 pump controller can cause issues with slow hydraulics just another thing in there
Pressure gauges, bypass tests and computer diagnostics can go a long way in determining the cause or causes. Will have to start somewhere. Better over test than over spend. Simon C