Heater Core Replacement at our Winter Haven shop

If it's plugged, sometimes yes. Sediment and old coolant deposits can restrict the passages enough to kill your heat while the core itself is still sound, and a proper back flush occasionally brings it back. If it's leaking, no. A flush moves debris, it doesn't close a hole, and the sealer products sold for that end up in the rest of the cooling system.

Not usually on its own, but it does change what you need to watch. You're losing engine coolant, so the level and the temperature gauge matter more than they did last week, and running low on coolant is how a small repair turns into a big one. The fogged glass is its own problem when visibility is bad. Get it looked at rather than topping off the reservoir all winter.

Because you're paying for access, not for the core. On most vehicles the dash, the steering column and the HVAC case have to come apart to reach a part that costs a fraction of the labor around it. That's the honest answer, and it's exactly why we confirm the diagnosis with a pressure test before quoting the job instead of guessing at it.

Not mechanically. The heater core carries hot engine coolant while the AC evaporator carries refrigerant, and a failure in one doesn't cause a failure in the other. They do share the same case behind the dash, though, which is why we'll ask about the AC before we open one up. Doing both at once, when both actually need it, saves you the labor twice.

It does, more than most people expect. Coolants use different additive chemistry to protect the metals in your particular engine and cooling system, and mixing types or topping off with the wrong one can gel the mixture or strip out the corrosion protection. Since that protection is what keeps a thin heater core from corroding through, using what the manufacturer specifies is the cheapest thing you can do for it.