Yesterday I found myself in a situation I have never really found myself in before... but first, a little back story.
My daily driver at this point is a 2004 RX8 and while it has had its fair share of issues it's only ever left me stranded a handful of times, always something little and fixable as soon as I got a ride to grab tools(fuel line came off the rail because I hadn't properly clipped it the night before and my clutch took a crap on separate occasions). I live in the panhandle of Florida and we VERY rarely see temps below freezing, much less a true hard freeze, we haven't had one since I've owned this car. We do have some pretty brutal summers though, so I have leaned towards valuing cooling over antifreezing properties when it comes to coolant, and I usually run 20/80 antifreeze/water and a bottle of Water Wetter.
On Monday night, temps were forecasted to be hanging in the teens for a decent number of hours so I went out in the ~30 degree weather once I got home and drained off about 3/4 gal of coolant and topped it off with pure antifreeze, ran the car for about 5 minutes and called it a night. Am I wrong in thinking that would be more than enough?
Come yesterday morning, I hop in the car to go to class, cranks first try, and drive off. About 3.5 miles from my house coolant temps start spiking, and quickly, I find a gas station and cut it off with coolant temps in the 265 degree range and steam coming from under the hood. At this point I'm assuming one of two possibilities, either A) Something froze and now I'm paying the price, or B) I somehow managed to not put enough coolant back in it and that caused the overheating, which led to all the coolant splattered about my engine bay and the huge puddle under the car.
Well after letting it cool down to temps I was willing to pop the cap on, I run into the gas station, grab a gallon of water and proceed to top it off again. I figured that since there was already coolant dripping from everything from it overpressuring the cap, it was a lost cause to try and diagnose in the freezing parking lot and limping it home to really check it out. It started right back up and I was off, keeping a close eye on my temps. Not even a mile down the road it had gone from 140 degrees to just north of 200 and I decide that's not working(no steam this time), and pull into another parking lot and cut the engine off, hop out and check the coolant level, and the reservoir is bone dry, which wasn't unexpected. The strange part was the lack of new coolant in the engine bay, or under the car...
Now at this point I call someone to come pick me up so I can grab another vehicle and make it to class. But I was seriously puzzled about what the issue was since I had 'missing' coolant. I figured either the possibilities were A) I managed to not fully top it off TWICE now, or B) I popped a freeze plug/coolant jacket seal and was dumping coolant into the oil pan, not onto the ground.
Long story short, towed the car home after all my classes and filled it again with stuff pulled out of the engine bay so I could get a better look at things then ran it to see where things were coming from. Nothing happened. The car came up to temp idling, I drove it around the block twice, I drove it around town with some serious pulls mixed in, never saw temps over 190...
I absolutely hate problems that fix themselves, they have no reason not to pop up randomly again, at the most inopportune times of course. So Oppo, what would be your diagnosis?