Is there a vavle that lets water flow into the heater core on 2001 Lincoln ls v8?

No, the 2001 Lincoln LS V8 does not have a valve that actively controls water flow into the heater core. Instead, the flow is controlled passively by the position of the heater control valve (or blend door). This valve regulates the *mix* of hot coolant from the engine and cooler air from the outside, directing it into the heater core. If the blend door is set to "hot," coolant flows through the heater core. If it's set to "cold," less or no coolant flows through. There isn't a separate on/off valve for the heater core itself.