A couple weeks ago, my Firebird overheated a bit. I had too much coolant in it, not enough water. But I shut it off before it got too hot, so no harm done. I replaced the leaking thermostat gasket and flushed the coolant out, and all was well. Well today, I drove to walmart, about 5 minutes, the car hadn't even fully warmed up yet. Once I shut it off, I noticed some smoke coming from under the hood. I saw that the heater valve was leaking onto the intake and the heat was causing it to smoke. I figure no big deal, a heater valve is only $15, I'll just buy a new one later. So I come out of walmart an hour later, and I notice a small puddle of coolant under my car. It was dripping down near the part of the exhaust that sticks out near the pinch weld on the passenger side, between that and the frame. I can't figure out what would make it leak there, unless I blew a heater hose, but they don't even run through that part of the car. Any help?

 

The heater core lines run through the firewall on the passenger side.
Could be dripping from a different location and following things down. At least with the car cold you could follow the path it's taking.

 

If something leaks on the firewall around the AC blower motor area (which would probably be the heater core in and out hoses for your case) that'll probably end up under the front subframe rail around the cat(s), which would be the pinchwelded area behind front passenger side tire. But also an inside leak (the heater core itself) ends up at the exact same place, happened to me. The coolant can seep under the carpet and through the floorpan unnoticable by the eye. Smell gives it away, ask me how I know

 

Hmm... that's interesting. I do smell coolant (or I think I do) when I have the heater on, but my carpet isn't wet. Plus I checked the heater hoses, they seem to be fine. And there was no coolant loss at all today, which is weird since I drove more than I did yesterday, and I had the heat on.

 

It could be a frost plug.. just a thought

 

No way, the motor is brand new, and I didn't even install the core plugs, the machine shop did that for me. I'm going to bypass the heater core since I really don't need heat anymore, and see how much of a difference that makes.