Fogging up your interiors windsheild? The smell of coolant in your vehicle?

Sounds like the heater core is leaking. At any rate you say it runs low on coolant. Hence a leak. 9 times out of ten, if you are smelling it, that is because the leak is from the heater core, which is located inside the passenger compartment.

no heat is probably low coolant or bad thermostat,although you have fog and smell ! the heating and cooling systems are closed systems the only way the windows fog is the coolant is hot and steams inside the car due to some leak inside the heater core box. as well as the smell being present. Now it is possible that a little leak has occured where the coolant supply or return line connects to the heater core and is running into the car which is running onto the core and creating steam and smell. hopefully it is a easy clamp tighten fix for you.

Check coolant level for radiator to see if it's going down. Does it smell like anti-freeze when the fog starts coming? Feel it, does it feel slightly oily?
If so, you may have a heater core problem.(Leak) Have the cooling system pressure tested to confirm.

If you are loosing coolant and you see water under the car after sitting you have a leak. The most likely area is the heater core as you are getting steam inside the car. If you smell anti freeze that is another confirming item. Check all the hoses and connections first before replacing the core. Good luck.

If you are talking about steaming up on the inside, you could have a heater core leaking coolant. Check the passenger side front carpet and see if it's wet. A big job to replace.