Friend's MT372D has a leak in the water pump. I don't know much about these tractors and need help in figuring out a solution. I notice that their is some kind of drain plug at the bottom of the shaft assembly where radiator fluid is dripping. When I start up the tractor, the fluid flows out from that hole. Is that an actual drain plug and what kind of plug goes in? Or is this a sign of a bigger issue for the water pump?