Good Morning;

I've got a '98 S70 with the non-automatic climate control. My question is that when I switch the heater knob from cold to hot, I briefly get a faint smell from the vents that quickly goes away. I can't tell if it's coolant or not. There is no smell at all when the knob is set to cold.

I pulled back the carpet etc and took a look at the bottom of the heater core, and there isn't anything leaking out. I got the system pressure tested about six months ago by a dealer, who said everything was fine. I'm getting no fog on the windows and haven't noticed any significant coolant loss.

I blasted the system with Lysol (into the intake plenum) in case it was mold but it didn't change. By the way, I do recommend the "crisp linen" scent...

So here's the question - is it possible for the heater core to be leaking given the information above? Is there some other cause for this smell (that only occurs when the heat is first selected)? My concern is that there is some super-slow leak and I'm gassing the family with ethylene glycol. Should I just let it go until I see puddles or coolant loss?

Thanks;
Matt