The heater core on your 1996 Ford Mustang is the part responsible for supplying heat to the interior of your car. If your heater core is not working properly, you may find that your windows don't defrost easily, your car doesn't heat up well or the passenger floorboards are wet with water or coolant. Repairing your heater core can be time consuming and labor intensive even for professional mechanics since many components have to be removed to gain access to the heater core. However, the process of replacing the heater core itself is not overly challenging.
Take the vehicle to a dealer or service shop and have the air conditioning system discharged.
Disconnect the cable from the negative battery terminal.
Place a coolant disposal container beneath the radiator. Remove the drain plug and allow the coolant to drain out of the cooling system.
Loosen the clamps on the heater hoses from the heater core inlet and outlet tubes at the right side of the firewall. Slide the clamps backward and disconnect the hoses.
Disconnect and plug the evaporator lines at the engine firewall. Plug the heater core tubes to avoid spilling any coolant during removal. Cap the evaporator lines to prevent the entry of dirt and moisture.
Remove the instrument panel by first removing the stereo. Then remove the dashboard trim panels with a trim tool. Remove the center floor console and the air conditioning and heater control panel. Detach the bolt securing the steering column to the steering shaft. Remove the nuts and bolts securing the lower half of the instrument panel to the driver's side door panel. Peel the carpeting back to access the bolts joining the instrument panel to the floor pan. Remove the two bolts securing the instrument panel to the passenger side door pillar. Pry out the defroster grilles and remove the screws securing the upper edge of the instrument panel. Detach any electrical connectors interfering with removal, then pull the instrument panel toward the rear of the vehicle to remove it.
Disconnect the main vacuum line from the heater/evaporator housing to the engine, located above the rear of the right valve cover. Pull the hose through the firewall into the interior.
Remove the heater/evaporator housing fasteners, which include a bolt near the top center of the unit, a nut at the top right, a bolt near the bottom, and a nut on the engine side of the firewall.
Verify there are no other wires or hoses connected to the housing. Pull the heater/evaporator housing out from under the cowl and remove it from the vehicle. Remove the four screws and the heater core cover, then pull out the heater core, being careful not to tear the foam sealing material.
Verify the original foam sealing material is intact and in place.
Route the vacuum supply hose through the dash panel and seat the grommet in the opening.
Position the assembled heater/evaporator unit under the cowl. Insert the heater core tubes, evaporator lines and mount studs through their respective holes in the firewall.
Install the remainder of the elements in the reverse order of removal.
Fill the cooling system with coolant fluid. Run the engine and check for coolant leaks. Re-charge the air conditioner system prior to operating.
