Q: What is a heater core and can I still drive my car until it's replaced?

Honda, nor any of the OEM manufacturers, does not sanction use of aftermarket sealers in the cooling system for "repairs". Unless your car has overheated, head gasket leaks are not that common and in any event there are tests to rule the head gasket in or out as the source of a leak or problem. The heater core is a little radiator that is built into the dash and through which flows heated engine coolant. A fan, that you control with a switch, blows cabin air over the heater core and the heated air then keeps the interior of the car warm in the winter. If the heater core is confirmed leaking you have three options: 1) don’t drive the car; if a leak does exist and opens up fully, the leaked material will make a huge mess, antifreeze will be in your car interior and you will incur added costs and the aggravation of cleaning up a huge mess if it is even successful (without ripping out the carpet, etc.); 2) detach the supply and return lines for the heater core at the firewall. Blow all liquid out of those lines and the core and cap them. You won’t have a heater and you can just fix it next winter if you want to (you also won’t have a defroster and that could be safety hazard even in non-winter months); 3) remove and replace the heater core. On your model, it takes around 6 hours to remove and replace the heater core. The Honda OEM core is recommended as the replacement but that is more costly than the aftermarket part that is typically installed. You can request the Honda part, though, of course. If you want the issue you are having fully investigated and diagnosed, and then have an explanation of your repair options and costs, please request a coolant leak diagnostic and the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.