When I had my Sportage I always used factory Kia thermasats, when I tried a parts store one it never worked right. The problem you first described sure sounds like a thermasat though.

That rad does make use of the factory rubber isolators, so it should be fine aside from the general dodginess of Chinese eBay performance parts.

If there's a leak between the tank and core of the rad, your HG just became a prime suspect. Plastic-tanked rads usually don't fail there (you generally will get cracks in the middle of the tank near the neck) unless you're getting pressure spikes, as you would from each combustion event injecting a little bit of blazing hot gas into the cooling system. And since Kia cheaped out on these engines and used a graphite HG (graphite is okay on an all-iron or all-aluminum engine but bad news on an engine with dissimilar metals) rather than the MLS style that Mazda originally used on nearly all the B and F series engines, they're a really common failure point and the layout of the ports between block and head mean that you rarely see the classic 'chocolate milk', it's almost always the tough-to-detect transfer between the combustion chamber and water jackets wreaking havoc on your cooling system (and catalytic convertor, those things don't like being doused in glycol).
The coolant hydrocarbon testers I mentioned earlier are fairly cheap (I think mine cost me like 30 Canadian pesos) and easy to use, and a head gasket is the kind of issue you want to either confirm or rule out ASAP.

Well, put a new a/c condenser fan on and so far, so good. But new issue, engine rattled and died, checked the oil and there was only a teeny tiny drop at the end of the dipstick, so, it was time for an oil change anyway, so I dumped it and replaced it, new filter, etc. When I poured the old oil into the new oil's empty jug, I see I get 4.5 quarts. So how on earth is my dipstick not showing this when the engine is hot. Checked level after oil change and dipstick shows full. So...??? Maybe it was crinkled up inside the tube and didn't reach all the way in, I don't know. Also changed spark plugs and, as always, oil in rearmost chamber. That's nothing new, I've had 3 Sportages and they've all had that issue, but never seen no oil on the dipstick. Oh, and as far as the aluminum radiator thing? I was actually looking for one made of copper, not too fond of aluminum, but the abuse it's going to see soon just makes me think a tougher metal is in order. Cheapest one I can find is a specifically designed performance radiator for about $205.

Someone mentioned this above, not sure if I was just talking too much while installing, but I feel like a huge noob at this point. I have changed multiple thermostats on Sportages. I've owned 3 and had to do this multiple times on each. Somehow, not paying attention or whatever, I INSTALLED IT UPSIDE DOWN!!!!! So, turned it over, now the cheap gasket is leaking, will replace today.

Edit---nevermind, I'm an even bigger idiot because I thought I put it in upside down!!!!!!! Ugh... It was just a bad thermostat. Like I thought originally... <img src="/forums/images/graemlins/shiner.gif" alt="" />

Nope, still have the same issue. It wasn't pushing out the cap and overflow tank with the a/c on because it was pushing out the thermostat housing due to the bad gasket. So, there are only a few options left - either the water pump is not circulating the coolant, the head gasket is blowing gas into the water channels, the radiator is too gunked up to actually cool the coolant, or lastly, there is a blockage in the block somewhere. Ok, so, the water pump, I can test that by removing the thermostat. I will do this asap. I really don't think the issue is the head gasket for two reasons - it only happens when the a/c is on (and yes, the condenser fan works great) and, I have zero water from the tailpipe. As far as the radiator being gunked up? Not really any way to test that, that I know of, just replace and run. If its a blockage in the block, I may be able to tell when I test the water pump. Or maybe not. Guess we'll find out. <img src="/forums/images/graemlins/shiner.gif" alt="" />

WHen this happens, you can usually see exhaust bubbles escaping the radiator(when filled to the rim) . and tHere are gas analysers that would indicate presence of combustion gasses...
Zero water from the exhaust is NOT a sign of anything....each gallon of burned fuel feeds the exhaust pipe with lots of water (MUCH more than a gasket leak) as a combustion byproduct...and you never see it in liquid form except when the exhaust pipe is cold and it condenses in the pipe....

I'm now experiencing the same issue. My radiator has been leaking slightly between the core and tank for a 4 months or so. yesterday at lunch time I noticed my temp gauge was reading 210 and it was only in the mid 60's. As soon as I came to a stop it was steaming out.

I put a gallon of water in before leaving work hoping to make it home and only made it about 10 miles. When I saw it reaching 220 I hit the next exit and puled into a business parking lot and called my roadside assistance for a tow home.

Weird thing was my overflow tank was full when I checked it after parking. I grabbed a towel I had and Carefully removed the radiator cap. Steam was all that came out. Makes me wonder if my thermostat is stuck shut.

Only 1/2-3/4 mile after leaving work it had got to 200 but went down to 190-195 so the t-stat must have opened but may have closed.

Ok, now I have definitely had that issue before. Basically exactly how you described. I replaced only the radiator and had no more issues. Your thermostat is probably ok, but they are so cheap I wouldn't recommend not replacing it also. I think the water in the rad turned to straight steam because it's not under any pressure if it's steaming out like that, plus you may have needed more than a gallon if the water that normally sits in the block was also gone. With only a partial fill, it will turn to steam faster and steam out of the gap quicker.

Now, I'm not sure if I mentioned it above, scanned over and didn't see it, but I drove to south Dakota and back in July and only had to top off the radiator every 2-400 miles and not adding much, but I drove 7 miles in city traffic taking my daughter to school last week with the a/c on for only the last 2 miles and it boiled out about a half gallon. Anyway, I got my new radiator, CSF 2 core copper and brass, no plastic at all. Installing this weekend as soon as I hook the rad hoses to some pvc and stick them in a bucket of water to test the water pump.

Picking up the T-Stat, gasket & new cap from NAPA after work. KIA dealer would had to order the T-Stat & gasket. I don't have time to wait.

New radiator should be here Friday from Rock Auto. I wanted an all aluminum but the place I was looking at was out of stock. I need my Sporty up & running this weekend.

Didn't think about the block being low or empty or plain water having a lower boiling point.

Last thing I might need is a gallon of coolant. I have about 1-1/2 to 1-3/4 50/50 at home. I buy a gallon of straight and a gallon of distilled water and mix myself. Much cheaper that way.