I 100% know this isn’t the correct way.
What is the reason the heater core is behind the firewall? To keep it out of the cold?
I have a vehicle that I don’t want to dump money into. It isn’t getting hot air from the drivers side. It blows hard but it isn’t hot. I was told it was the heater core from a shop. I tried to flush the heater core twice. It didn’t seem clogged as water flowed freely (just an observation).
Can I just buy a heater core and mount it inside the engine bay instead of tearing the dash apart?
To address your original question, the heater core, and also the ac evaporator, is inside a box in the cabin which the blower motor is also attached to. You get heat—or cooling—by having the blower move air across the hot heater core or the cold evaporator. Mounting a core elsewhere would do nothing because it would no longer be integrated into the hvac box or connected to the ducts and vents
The heater core is in front of the firewall because you are in front of the firewall.
You can bypass the heater core by connecting the inlet and outlet hoses together.
Would that still produce heat in my cabin?
No, but it would let you drive the car until you can replace the heater core. You can buy a propane heater at most hardware stores if you need to stay warm. Be sure to open a window some…
No
If its just one side its likely just a problem with the blend door, don’t replace your heater core
I took it into the shop for a blend door. Was told it was the heater core
If the heater core is your problem, it’s not that it’s plugged. My 99 Sierra, every now and then, won’t heat the cabin. It’s due to a buildup of mineral that insulates the core enough to impede heat transfer. I flush the core with a few gallons of vinegar, which dissolves the mineral. I rigged a 1/6th hp utility pump connected to one heater hose with the other hose dumped into a bucket. 2 gallons of vinegar (a mild acid) gets pumped through until whatever returns to the bucket stops fizzing. Then, I dump that neutralized vinegar and refill the pail with another 2 gallons. Rinse and repeat. I do it once every 3 years or so.