I have a blown coolant seal, but the symptoms don't show up until the thermostat cracks open. I waved a smog wand over the filler neck and got 60 ppm on the HC's.

Normal operating temperature was about 95c and the coolant just slowly spilled its way out of the puke tank until the car was shut off, after that if I tried to turn the car back on shortly after I would get the low coolant buzzer.

For no real reason other than "just because" I did the fan mod yesterday. Now operating temp is at 85-87c even when pulling hard.
To my suprise the puking stopped, the buzzer stopped screaming after a shutdown and restart, coolant levels are normal after checking several hours later after shutdown. I can beat the **** out of the car and the coolant stays in except for the normal amount for expansion. I haven't checked the HC count yet... but what the hell is going on?

Next thing you know a fan mod will cure cancer.