I just purchased this Komatsu Excavator. I noticed the swing speed was a little slow. Measured and it is about half the rated speed. Did some research and found the swing and blade are driven off the same section of the pump. Checked the pressure and found the swing at 12Mpa where the spec is about 20Mpa, and the blade gets up to 15Mpa where the spec is almost 22Mpa. From what I've been told, these pumps rarely just get weak, they tend to work or fail catastrophically. Not sure how true that is, but have heard it from several people. I also find it unlikely that the pump can build up to 15Mpa for the blade, but only 12Mpa for the swing. I believe the problem lies elsewhere. All other pressures measure good. All other speeds seam normal, I didn't actually follow the testing procedure for those.
I tried to locate the swing/blade pressure relief valves, and narrowed it down to two that I though possible. The Shop Manual shows a picture that is unhelpful. I can positively identify the main relief valve for the main hydraulic section. I removed and cleaned the two valves I thought likely. I saw no indication of contamination. I tried adjusting them each a full turn, which should have given a clear increase in pressure, but my swing and blade pressures remained the same. The swing motor has it's own relief valve (which is how it lowers the pressure down to 20Mpa) so I didn't bother checking that because it wouldn't affect the blade. Either neither of those valves were for the swing/blade or that is not the problem. The only idea I have left, is a restriction in the suction line, possibly the inlet screen in the tank. I will drain the tank, clean the screen, and put in a new hydraulic filter when the new filter and oil arrives.
I have a background in auto and med/heavy trucks. I have a full understanding of hydraulic system theory, but very little hydraulic system experience beyond repacking cylinders, replacing hoses, replacing pumps, and changing filters. Does anyone have any other ideas of what I could check? Or maybe point me to the correct swing/blade relief valve.
Thank you,
Jeremy
I tried to locate the swing/blade pressure relief valves, and narrowed it down to two that I though possible. The Shop Manual shows a picture that is unhelpful. I can positively identify the main relief valve for the main hydraulic section. I removed and cleaned the two valves I thought likely. I saw no indication of contamination. I tried adjusting them each a full turn, which should have given a clear increase in pressure, but my swing and blade pressures remained the same. The swing motor has it's own relief valve (which is how it lowers the pressure down to 20Mpa) so I didn't bother checking that because it wouldn't affect the blade. Either neither of those valves were for the swing/blade or that is not the problem. The only idea I have left, is a restriction in the suction line, possibly the inlet screen in the tank. I will drain the tank, clean the screen, and put in a new hydraulic filter when the new filter and oil arrives.
I have a background in auto and med/heavy trucks. I have a full understanding of hydraulic system theory, but very little hydraulic system experience beyond repacking cylinders, replacing hoses, replacing pumps, and changing filters. Does anyone have any other ideas of what I could check? Or maybe point me to the correct swing/blade relief valve.
Thank you,
Jeremy
