I recently noticed a slight orange discoloration in my hhr passenger floorboard. There was no noticeable wetness and when I pressed my finger in an attempt to see if there were in moisture in the foam under the carpet my finger came back dry, BUT it smelled of coolant, I immediately thought heater core, but really? just after 2 years of use?. First I checked my fluid levels, and the reservoir and the neck that the pressure cap screws into were low. I filled them and marked a cold fill line in black marker on my reservoir. After a couple of days of moderate driving I've noticed that the coolant in the reservoir has moved slightly (not a huge amount, maybe less than a qtr inch) below the mark when cold. Also there is no moisture under the carpet and no noticeable leaks that I can see. I'm going to keep a check on the floor and the coolant level in relation to my mark. My main concern is, how did this coolant leak to my passenger floorboard in the first place, maybe a pinhole in the heater core? any other possible ways on this model, i.e. hoses, or fittings in the area? And lastly does anyone know of a good "how to" on replacing the heater core in the hhr with pictures?