580 case backhoe

I just bought an old 1975, case 580b backhoe and the backhoe attachment will only swing to the right. If I hold the left foot pedal down to swing it to the left, it will only move if I move one of the hand controls for backhoe just slightly. My thinking is that something is wrong with the control valve for that left pedal and when I move one of the backhoe hand controls, Oil is bypassing and being back fed from one of the hand controls. Does anyone have any suggestions as to what the problem would be.



Thanks in advance.