Originally Posted by 1989comanche
Definitely sounds like your heater core is getting ready to take a dump on you.
Yes, heater core. The key words here "getting ready". Even a very small leak will produce a smell. One small enough to cause fogging and smell but not yet large enough to dump the engine coolant inside.
I always like to take the "if it was mine" approach. So, I would double check all the hoses and components of the cooling system under the hood. When they check out I would then do an "old school" trick. Remove the inlet and outlet hoses and make up a temporary bypass loop. Give it some time and see if the smell dissipates and the fogging gets better. If so, then order a heater core and start taking things apart behind the dash to figure out what is leaking. Leave the heater core in it's packaging just in case it is a bad line or something so you can return it.