How to Remove a Heater Core in a Chevy Blazer. The Chevrolet Blazer has a single heater core that blows warm air through the ventilation system. Over time, sludge from the cooling system (where the heat is derived) accumulates in the core, leading to leaks and eventual failure. When it fails, removing the heater core can be challenging. The average backyard mechanic will spend about four hours on the removal.
Disconnect the negative cable from the battery.
Open the drain plug at the bottom passenger-side section of the radiator. Open the radiator cap, and let the fluid drain until empty.
Unsnap and remove the front dash panel. Unscrew and remove the bottom panel and unbolt the main dashboard harness from the firewall at the windshield. Take out the radio, gauges and most of the switches and accessories to gain access to the main bolts.
Remove the coolant overflow tank, main computer and blower-fan housing from the passenger-side engine compartment. This may require several sizes of sockets, socket extensions and a Phillips head screwdriver. The computer will uncouple from the truck in the rear of its housing.
Uncouple the heater core hoses from the core by loosening the hose clamps.
Remove the bolts on the interior, between the dashboard and firewall, and the two bolts in the engine compartment behind the main computer. On some models, these bolts can be between the passenger-side fender and the engine bay.
Slide the heater core out toward the windshield.