You should drain the engine's coolant, unhook the negative
Battery Cable and wait two minutes for the air bag system to finish discharging, if your vehicle has air bags. Remove the instrument panel silencer from the driver side of the instrument panel and unhook the heater hoses from the heater core tubes (7). To do this on an LHD model, remove the
Blend Door Actuator (1) from under the driver's side air distribution housing (2), but on a RHD model, pull the parking brake bracket aside and detach the steering column. After that, remove the two screws (9) connecting the flange (8) to the front half of the HVAC housing (10) and remove the flange. Using absorbent towels will prevent engine coolant from ruining your carpeting. Cut the clamps (3) holding the heater core tubes to the heater core (5), unhook the tubes and throw out the O-ring seals. Get the heater core tubes out of the dash panel and seal up the heater core ports with plugs or tape once you're done. Take out the screw at (6) that is securing the bracket (4) to the housing (2) on the driver's side and take the bracket out, after which you can carefully remove the heater core from the housing. When installing, add the new heater core (5) into the air distribution housing (2) on the driver side and put the retaining bracket (4) back in with the screw (6) tightened to 2.2 N.m (20 in. lbs.). Completely remove the tape or plugs from the heater core ports, moisten the new rubber O-ring seals with clean engine coolant and carefully fit them on each of the tube fittings of the heater core, being sure to use only the correct O-rings. Slide the heater core tubes (7) under the cover area and onto the heater and then secure them with the two retaining clamps (3). Attach the flange (8) to the heater core tubes inside the HVAC housing (10) by tightening the two screws (9) to 2.2 N.m (20 in. lbs.). LHD needs you to replace the blend door actuator (no. 1) and reinstall it; on RHD, you will replace the steering column and parking brake bracket. At last, install the silencer for your instrument panel, attach the heater hoses to the heater core tubes, secure the negative cable to the battery, flush the cooling system when replacing the heater core and refill the system with new coolant.