Jeremy,
I just replaced my radiator Thursday for the second time in the life of the car. The driver side end tank was cracked hear the fan shroud bolt near the top. That is the same place the OEM radiator cracked. My guess is that the same company supplies the end tanks for both sources. I found a replacement at Pep Boys for $149.99. It was a GoDan (GDI) 2162 that also included the transmission cooler in the passenger side tank. You can find them for as low as $100 through the internet, but I needed one more quickly than that could provide.
You can look for coolant trails to find the source, but most likely it is the end tank seals or a crack in the end tank. Check the easy things first: upper and lower radiator hoses. It's not too tough to swap the radiator. Just disconnect the battery before you touch the connections to the alternator. These had to come off mine to allow the old radiator to come out. Unfortunately, I grounded the alternator's power supply cable an blew a wire at the starter relay on the driver side fender. A check of the electrical schematics showed me where to look for the wire or fusible link. Surprisingly, the wire blew before the link did. Good luck with locating the leak or a replacement.
After our little "near biol over" in Austin, I went ahead an replaced all the hoses and t-stat again to make sure they were okay, so I doubt it is that..I suspect it is indeed the radiator leaking onto the front header...
