... antifreeze from a leaking heater core for an extended time? I drove for about ten hours breathing in what smelled like burnt antifreeze. it was a vapor coming through the vents into the cab area. i had the windows open a couple inches for ventilation but pulled over and stopped when I started having bad chest pains. After breathing fresh air for a few minutes the pains went away. I have been real tired for a couple days with sore muscles but have felt a little better today.