I was given this Maytag washer by a friend who had replaced it a couple of years ago. She said she replaced it after a repairman told her that it needed a new motor. Anyway, when I got it home I hooked it up and it ran just fine initially. However, after washing a couple of loads it stopped mid cycle and the motor was making a loud humming noise. The machine had completed the wash cycle, drained, and refilled with water at the start of he rinse cycle. However, when it was supposed to start agitating again the motor would just hum. This machine has an exposed belt drive underneath the unit. I tilted it back and removed the drive belt. When I pulled the knob to resume the operation the motor started running. I reinstalled the belt and the machine operated normally. Apparently this was the problem that the previous owner had with the machine. It would stop mid cycle and the motor would just hum. How should I troubleshoot this problem.