How about a new old car

[Maengelito]

\bingo
look in the expansion tank for ring around the collar
in my car is was blackish
also same type of stuff around the gasket on the radiator cap.
get it good and warmed up, and give it the sniff test to see if you detect a faint coolant odor
look for bubbles in the expansion tank when it is running hard

after my last session at VIR-N, i was really low on gas so i came in early to not fuel starve the car. i drove it around for a little bit, but not nearly as much as a cool down lap. when i parked it and raised the hood to get some more air flow to cool down, i noticed the expansion tank was bubbling. i figured that was a combination of it being crazy hot that weekend, the miata's less than spectacular cooling system and not doing a full cool down lap. think its something more serious like a blown head gasket? i'm not low on coolant, so i dont think its goin anywhere. and for some reason (i guess its the iron blocks) you always get some nasty crap in the expansion tank no matter what. i think evan has the same problem.