Smoke/Smell out of air vents?

[Dolphins39]

I recently changed my cylinder heads and now whenever I drive I also get a smell coming out of the air vents in the car, even when I have it in the off position. I have a 92 4.0L explorer. Sometimes there will seem like some smoke coming out. I still have some oil left in the cooling system from when the heads were cracked which I have repeatedly tried to flush out and the amount seems to be getting less and less. My oil looks fine when I check the dipstick. I was thinking maybe the oil in the cooling system was getting hot or something and burning off. Any ideas?

 

[shamaal]

Generally speaking the cause of mist from the vents is as a result of the heater leaking. The mist and smell is the coolant. Possibly fixing the heads increased the cooling system pressure.

Luckily changing the heater core is easy and inexpensive:

http://www.explorerforum.com/forums/showthread.php?t=160622