Vents blow cold until fan kicks on?
 

I've been resurrecting an '01 Bpxster and just started driving it. Yesterday the guage was reading a tad over 180 but the vents were blowing cold even though the thermostat was set on 85. When the fans kicked on it instantly started blowing hot air. I'm fairly mechanically inclined, but this problem perplexes me. Then last night the temp gauge pegged out and further inspection revealed it was out of coolant. The trunk was wet above where the cap resides, however there wasn't evidence that the bottle is cracked because it wasn't wet. Any thoughts?

I'd try replacing the tank cap, which is the equivalent of a radiator cap in a normal car. If you are lucky, that is all it is.

Hopefully you didn't damage the engine when it overheated...

I got mine cross threaded once and caused some issues with the car running hot.

I did the same thing cross threading. High temp light came on but gauge read ~180. Re threaded the cap and everything was fine. Also make sure it is the newest cap
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