I dont know what the hell the P.O of my truck was thinking. But I noticed on one of the hoses that goes From RAD. to heater core it had a HOSE VALVE. The ones you turn that handle and it stops flow. I discovered it because we're barely getting winter weather here in South Texas and I noticed there was NO HEAT coming through. So went under hood and opened the valve and BAM the heat started flowing. Does anyone know why the P.O would do this? I thought maybe for leaks etc. but there arent any.