If the heater core of your 1990 Chevrolet truck begins to fail, heater core liquid can begin to leak out into the interior of the vehicle. One result is that your air conditioner might not be able to blow warm air. A broken heater core might even spew white smoke if you try to use it. If your vehicle has any of these problems, it is time to change the heater core. Experienced home mechanics can do the job themselves in several steps.
Remove the keys from the ignition and open the hood. Disconnect the truck's battery with a wrench.
Place a drain pan under the radiator and engine drain plugs. Wait five minutes for the fluids to cool down. Loosen the plugs and allow all of the fluids to flow out. Close the drain plugs.
Open the radiator cap and pour radiator flush into the radiator. Follow any special instructions found on the radiator flush you are using. Let the engine run for a few minutes, then turn it off. Open the drain plugs and let the fluids drain out. Close the drain plugs again.
Pull the hoses off the radiator. Remove the screws at the rear wall of the engine with a cross-head screwdriver.
Remove the glove box and lower right-side knee bolster by removing its securing bolt and screw. Pry off the knee bolster with a slotted screwdriver.
Remove the heater core mounting bolts, then remove the heater core. Be sure to disconnect the heater core's electrical connector. Install the replacement heater core into the truck and connect the electrical connector.
Reassemble the glove box, knee bolster, dashboard and heater case screws. Add DEX-COOL coolant to the radiator until it reaches the "FULL" line and reconnect the truck's battery.
