Coolant leak, light flashing, fans running!

[nola911]

Ok guys, if you have any advice or suggestions let them fly. It started 2 months ago with a coolant leak behind the right rear tire. The tank never drained past the full level. I figured it was overfilled and some came out the overflow (if there is such a thing). There was no moisture in the trunk and no puddles under the carpet. The tank itself is not damaged.

Now, it has been 2 months and maybe 100 miles since then without incident and absolutely no puddles in the garage... until this weekend. The whole tank emptied out similar to before behind the rear tire. Today, I put two cups of water in it expecting it to rush out a bad hose, but it did not leak. The water was not even half full in the tank. I started the car and let it sit for 15 minutes. It ran fine for a while, then the tank started filling with coolant from somewhere else in the system. As it did this, it overflowed itself and started leaking and the thermostat started to near the third temp line (over 180).

I turned it off and summoned the Bently guide and 986 forum search for ideas. Having struck out, I went back to it. Now, with the tank miraculously at the typical fill level, I restarted the car and took it out of the garage thinking it might be the hot single car garage that was making it hot. I drove around the block. As soon as I made the first turn, the red light on the right of the temp started flashing and the fans started running. It ran a little hotter than usual (near the third line), but not getting near the top temp. By the time I made it back home, the fan was running harder.

Am I correct in asuming the light flashes if it is too hot OR if the radiator has no fluids?

I read of leaves or debris sometimes block radiator flow, but my garage queen has no such debris.

Any help is deeply appreciated. I want to avoid the 300 dollar tow fee to porsche if it is something minor that I (or local german repair shop) can handle.