yes, it's possible from a leaky heater core, to make sure remove the surrounding carpets pressurize the system you must detect the leak because its present you can smell it.
i prefer to use liquid radiator sealant not the powder type, and use good known brand, it can seal only the small leaks. you can try.
Check our diagrams below how to replace heater.
let us know if you need more help.
Images (Click to enlarge)
Friday, February 12th, 2021 AT 10:32 AM