How to Replace the Heater Core on a 1979 Chevy Truck

by Russell WoodUpdated November 07, 2017

Items you will need

  • Flathead screwdriver

  • 3/8-inch ratchet, extension and socket set

  • 50-50 pre-diluted coolant

  • Replacement heater core

The heater core on a 1979 Chevrolet truck acts just like the radiator on the front of the truck, but it does the job slightly differently. The heater core takes the coolant that circulates from the engine and circulates it through its core. The heat is then blown out with the blower motor through the dash vents. If the heater core breaks, coolant can leak into the truck. To fix the issue, replace the heater core. The job should take about an hour for experienced home mechanics.

Let the engine cool. Open the hood of the '79 Chevy truck and locate the heater core tubes. They are on the passenger side of the firewall and stick out next to the blower motor box. Remove the hose clamps on the heater core with the flathead screwdriver, then pull the lines off of the heater core tubes.

Open up the passenger door and locate the climate control box under the dashboard. Disconnect the temperature door cable from the distributor duct adapter with your hands. Unbolt the metal fender liner from the fender with the 3/8-inch ratchet and socket. Pull the fender liner out of the fender well, revealing the heater core screws.

Unbolt the heater core case screws, working through the fender with the 3/8-inch ratchet and socket. Unbolt the heater core from the case with the 3/8-inch ratchet and socket and take it out of the case.

Install the replacement heater core into the case with the 3/8-inch ratchet and socket. Install the case back into the dashboard with the 3/8-inch ratchet and socket, then reconnect the temperature door cable.

Install the heater hoses onto the heater core on the firewall with the flathead screwdriver. Open the radiator cap and then fill the radiator with the 50-50 pre-diluted coolant. Turn on the engine, then turn the heater on to its highest position.

Look for any coolant leaks in the system. Let the truck get to normal temperature, then turn it off and let it cool down again. Open up the radiator cap again and fill with coolant if necessary.

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