Car overheating but heater blows cold air — what does this mean?

Overheating + cold heater almost always means **low coolant or air in the cooling system**. Here's why: The heater core is the highest point in most cooling systems. When coolant is low, the heater core is the first thing to run dry → cold heater. Meanwhile, the engine is still generating heat with less coolant to absorb it → overheating. **First steps (in order):** 1. Let the engine cool COMPLETELY 2. Check the radiator cap (not just the reservoir) — it should be full when cold 3. Top off with 50/50 coolant 4. Look under the car for any puddles or wet spots 5. Check the oil cap for milky/chocolate residue (head gasket indicator) If you keep losing coolant with no visible leak, then yeah, head gasket is on the table. But most of the time it's a cracked hose, bad radiator cap, or leaking water pump. Don't jump to the worst case yet.

On the '09 Accord specifically, check the radiator cap. Honda caps from that era are known to fail. A bad cap lets pressure escape, which lowers the boiling point of your coolant. $12 fix that solves a lot of overheating issues.

If it turns out to be air in the system, Honda's have a bleeder bolt on the thermostat housing. Fill from the radiator cap, open the bleeder until coolant comes out, close it. Way easier than the squeeze-the-hose method. The [2009 Accord repair guides](/repair/2009/Honda/Accord) should have the cooling system bleed procedure.