PC390LC-10 (SN:A30059) 8500hrs Our 390 is acting a little strange need some advice on where to start looking. The boom down function will not lift the machine off the ground. Doesn’t mater where you place the stick in relation to distance from center of machine. It does have the toggle switch to allow you reduced pressures for boom down to make pulling a flat grade easier but that being switched from one to the other has no effect. It digs fine with plenty of power in the stick in and out just the boom down is weak. Also worth mentioning that the pump whines under a load like it’s cavitating but we’ve had that looked at by the dealer and they’ve said it checked out. We’ve replaced filters and have had pressures cjecked but I’ve never felt at ease with this. In the two years since that was checked the machine has done fine. This just seems to be the only new thing that’s come up. Otherwise this has been a great excavator.
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