Remove the heater core access cover screws.
98 blazer heater core removal.
Pretty easy to do.
Remove the heater core intake and return hoses from the core nipple by releasing the squeeze clamps using channel lock pliers.
Remove the heater core hoses on the upper left of the engine bay by pinching their hose clamps with a pair of pliers and pulling them off.
How to replace heater core on my 1998 chevy blazer.
Disconnect all of the vacuum lines from the heater assembly.
Once panel under dash is removed you will see the heater box remove the 6 8 bolts around the very base of it it will able to be lowered down and you will see the heater core it has a couple of brackets that hold it in place remove these.
Remove mounting bolts holding the heater core cover in place using swivel sockets and extensions.
Some models will have screw type hose clamps.
Turning them counter clockwise will loosen them.
Remove the hvac module from the vehicle.
Squeeze the clamp and slide and twist the hose as you pull them off.
Disconnect the heater hoses under hood.