1. Open the hood of your Explorer and locate the engine bay.
2. Identify the heater core, which is a small, rectangular box located on the passenger side of the engine compartment. It will have two hoses attached to it, one inlet and one outlet.
3. The heater inlet line is the hose that connects to the top of the heater core and runs to the engine. It is usually black in color and about 1/2 inch in diameter.
4. To replace the heater inlet line, simply remove the old hose by loosening the hose clamps at both ends. Then, install the new hose and secure it with the hose clamps.
