The Chevrolet Blazer uses routed coolant lines and a heater core to warm the air inside the cabin. This embedded core can clog and leak, requiring replacement. The entire dashboard must be dislodged at a minimum, to gain access to the core mount bolts and remove the core itself. The average backyard mechanic can replace a heater core in a Blazer in about four hours.
Chevrolet Blazer Repair the Heater Core Instructions
1. Disconnect the battery by turning the positive terminal in a counterclockwise direction. Store the terminal away from the battery.
2. Drain all coolant from the system by turning the petcock on the radiator counterclockwise, then allowing the coolant to drain into a pan. Turn the radiator cap counterclockwise to release any latent pressure.
3. Remove the front dash cover by turning the bottom mount bolts counterclockwise, then pulling the cover free from the pop rivets holding to the dashboard. There is one screw on the underside of the dash gauge cluster lip that must also be turned counterclockwise. Maneuver the cover out of the Blazer and store it away from the work area.
4. Release the dashboard from the primary bolts at the firewall by turning them counterclockwise. They’re located between the dashboard and the front windshield; there are between four or eight, depending on the year. Once free of these bolts, the dash will come loose and can be moved forward.
5. Release the heater core hoses from the firewall by turning the hose clamp screws counterclockwise, then pulling the hoses free from the core nipples. The hoses are sized to the nipples and cannot be replaced in the incorrect order.
6. Remove the bolts that hold the heater core in place by turning them clockwise. Some mechanics insist that the dashboard must be taken out completely, or that the inner fender must be disassembled to reach these bolts, but this is normally not the case. The core comes loose once the mount bolts are removed, and the unit can be lifted out toward the windshield.
7. Replace the core with a new unit, then position it into the dash by lowering it into the firewall area and placing the nipples through the open holes to the engine compartment. Tighten all mount bolts clockwise. Push the dashboard into position, then tighten the firewall screws clockwise until they are snug. Replace the front dash cover and secure the bolts, not forgetting to turn the gauge cluster lip screw clockwise as well. Replace the hoses to the heater core nipples and tighten their hose clamps.
8. Turn the radiator petcock clockwise, then refill the system with coolant. The system will most likely take in more coolant than was drained, because the hoses and core are totally empty.
9. Reconnect the battery by turning the positive terminal bolt clockwise until it is snug.
Read more : How to Repair the Heater Core on a Chevrolet Blazer
