Anything that can make its way into the heat exchanger system can be smelled in the cabin area yes.
You can check for rusty spots and holes in the exchangers, but don't underestimate the power of loose heater hoses. Double check the clamps and hoses and make sure they're tight, don't have tears or rips or aren't split. Mine had splits from the previous owner, I replaced them and the air flow and heat were 20x better.
