Toyota 87107-35060 Unit Sub-Assy, Heater Radiator

You can start the process by taking apart the heater core. It works best if you first take out the evaporator assembly, which needs you to disconnect and collect the refrigerant. The factory says you should take off the whole instrument panel and reduce the steering column height, which means working with many electrical links and risking damage to tiny plastic parts that home mechanics might break. You can get to the heater core that runs the back AIC and heating for 4Runners by taking both front seats out. Start by taking off the battery's ground cable, remembering to use the right code for unlocking your stereo if it needs it. After your engine cools down, remove all the liquid from your car's cooling system. At the firewall in the engine area, pry the heater hoses loose from their connections, while pushing the rubber seal inside the vehicle and closing the heater core with a plug to keep water from leaking. Start taking apart the interior starting from the center console, glove compartment, and its liner. Get the ashtray, radio, and center dash bezels off as well, and finally remove the instrument panel, along with its reinforcement brace. Pull out the ECM without disconnecting its wires to make space below the heater core housing, while taking the dash panel heating controls off first. Release control cables from the heater box, undo and extract the central ventilation duct, then remove the lower central duct. Untighten the screws linking the heater tubes to the housing, and then carefully pull the heater core from the housing. Put towels or rags under it to catch the dripping coolant. Pull the assembly out gently to protect the plastic pieces, and remove the parts only when there's enough room for the plastic tabs to pass by anything that might block them. We put the parts back into place in the opposite order we took them out, then top up the cooling system before reconnecting the car's battery and driving it to double-check everything works right.