Auto Air Conditioning & Heater Repair: Coolant leak into car, heater core replacement, coolant line

Question
Hello my car is a 1997 Kia Sportage, recently last week I stopped my car at the mall to park in a spot, once I turned the car off smoke began to come out of all the vents, I got out of the car and waited a bit but I did not see the smoke coming from the engine, I opened it up and nothing was there. Once I took a good look at the car I noticed a green colored liquid spilling into the floor of the front seat passenger side.  I am assuming this is coolant since that is the only thing that color I recall ever seeing go into my car.  I went at head and drove home to park my car and tried using the ac, immediately smoke came out again and the green liquid began to gush out on to the floor in the front passenger seat area again.  I bought this car used last February and I have never had any issues with it, I have done all the required oil changes on time and I am due for one on the 2nd of next month, can you tell me what can be causing the cooling to be sent into my car and what is causing the smoke, perhaps the coolant burning in my engine, I did fill my car up with water the last time I drove it thinking that the next thing will be for my radiator to crack or something.  Any info you can give would be greatly appreciated, thanks so much.

Answer
December,
There are only two possibilities that could be causing it to leak into the passenger compartment. The first would be that you may have had the coolant line leading into the heater core may have come off or cracked allowing it to leak out.
The second, and what I feel is more probable because of your description... I believe your heater core itself has cracked and is leaking.
I haven't replaced one on a sportage before but I will give you a rough estimate from what my "charge this book" says it would cost. I am not certain how mechanically inclined you are, so that is your call as to whether you would like to attempt it yourself, but here is what you are looking at...
5.8 hours of labor for the heater core replacement. At the average of 68.00 per hour this comes up to 394.00
The shop price for the heater core is 144.00
So all told you are looking about 538.00 to have the core replaced.
This is on the low end. If the shop will need to recover the refrigerant in your a/c system (because the heater core and the evaporator are in the same housing, you may not be able to get one out without the other) you can expect about another 150-200 dollars on top of that. My literature says that it isn't necessary, but as I said I have never had my hands in a sportage.

I hate to be the bearer of bad news, but this is what I am seeing.

Now if you should decide to attempt to do it yourself... I will be more than happy to help in whatever way I can over this forum. My literature says that it is not too terribly in-depth of a task, but again, I do not know your level of experience. I am sure there are also KIA experts in this forum that you could pose questions to also that will be happy to assist.

And by the way... thank you for your excellent description. Very rarely do I get one that detailed. It makes this process so much easier on all of us in this forum.

Thank you for your question. If you found this response at all helpful, please remember to rate it. If I can do anything further now or in the future, please do not hesitate to ask. Thank you again, and good luck in everything.