But the front heater core uses non toxic coolant while available at auto part stores around the region and although it is non toxic when is fresh one has to dispose the used coolant properly. The process of removing the heater core is problematic for home mechanics as it contains a lot of bolts and some of them are rather hidden so considerable amount of mechanical experience is advised. Initial the air conditioning system should be discharged and the refrigerant reclaimed at a dealer service department or automotive air conditioning business. Termination of the negative battery terminal and pulling out the coolant on the radiators. For removal process involves the withdrawal of the heater/evaporator housing which involves full withdrawal of the instrument panel and support tube. It not necessary to demote the floor console and instrument panel but for certain models, it may be necessary to demote the windshield wiper motor and cowl tray. Take off the refrigerant lines and coolant hoses from the heater core tubes, if they are too long, they must be cut. Take out the steering column and the shift lever, retract the carpet to take off the floor air ducts and take off the shift cable. On specific models remove PCM and body control , fuse and relay box should be removed. Take out the cross-cowl tube and all the little air ducts; deroute the wiring harnesses, and take out the heater/evaporator housing. Remove the heater core from the housing, by basically pulling it backward and install is done in reverse order while making sure new O-rings are used for the evaporator refrigerant connections. For the rear heater core, only for 2004 Highlanders, remove the right rear floor panel, weather stripping, and trim, and the heater hoses and air ducting. For 2007 and earlier models, disconnect the electrical connectors, remove the heater assembly plate and the heater core. On 2008 and subsequent models get the air conditioning out of the system before disconnecting the heater core tube of the retaining and supporting brackets. For PTC heaters, the quick heater is removed from the passenger's side on highlander models and the driver's side on Lexus models, some trims and duct fasteners needed to be removed before disconnecting electrical connections and sliding the heater assembly out. Installation of all the components is carried out in the opposite manner of disassembly, after which the level of the coolant is checked and connections to the hoses for leakage.