To replace a heater core, disconnect the negative battery cable, wrap the end of the cable in a towel, and keep the cable away from the battery. Drain the radiator, and locate the existing heater core. Disconnect the hoses and wiring connected to the heater core, taking note of the position of each wire and hose, and install the new heater core. Reconnect the hoses and wires, refill the radiator, and connect the battery to test the new heater core.
The specific location of the heater core varies depending on the make and model of the vehicle, but most heater cores are located near the back of the engine or under the dash of the car. Remove the glove box, dashboard cover, or air compressor to access the heater core if necessary. Refer to the owner's manual for the vehicle to determine the specific location of the heater core if it isn't easily located.
To drain the radiator, remove the plug on the bottom of the radiator. After installing the new heater core, tighten the drain plug before filling the radiator and overflow reservoir with the recommended coolant. Place the cap on the radiator, and turn the vehicle on to check the system for leaks.
After reassembling the vehicle and connecting the battery, start the vehicle to ensure the new heater core is working properly.