My 2004 Blazer is giving off the smell of coolant inside the passenger cabin. It's most pronounced when the engine is cool and I have the heater on. The smell seems to diminish as the engine warms up. There doesn't seem to be any evidence of a leak (no puddles on the ground under the truck, no wet floor under the dash on the passenger side). The engine doesn't seem to be overheating, and the heater heats like a blast furnace, as usual.

 

I'd throw a cooling system pressure tester on it....pump it up to pressure...wait... then come back and observe if it held or dropped

 

my daily driver has been this same way for a while. my guess is the heatercore is just barely starting to leak, so maybe a drop or two comes out within a few minutes and the heat just evaporates it before it can drip on the carpet.

 

Addendum to the list of symptoms.

The windshield is fogging (but not heavily up to this point), and I'm detecting a sloshing or gurgling sound from under the cowl on the passenger side; the sound is most pronounced on acceleration, especially after the engine has just been started. Still no moisture on the passenger side floor or any other visible sign of coolant leakage, and still no overheating--YET.

 

Foggy windshield is the blower motor blowing coolant that leaked from the heater core onto the windshield...replace your heater core.

 

Look under the engine compartment near the passenger side firewall for a drain for condensation. Use a wire to make sure it isn't clogged and drains freely. Be careful with that wire. You don't want to cause any damage. Trash can build up and clog the drain.