Boiling over

It could be your radiator cap but I think it may be new radiator time!

Get yourself an aussie built "twin cooler" from Flyin Miata, these crazy items cost us locals $1400 but only cost $500 or so once shipped to the states :shock:

When mine did that it was because my endtank on my radiator crapped out. . . and then took out my headgasket.

Pressuretest the radiator, and check for oil in your coolant and coolant in your oil would be my guesses.

theres also an exhaust leak dye tester available thru dealerships to test for these overheat probs.
the prob may simply lie in your head gasket. not so simple actually. if exhaust gasses bypasses into ur water system,it contaminates and overheats it, eventually blowing the head and destroying ur water system as well. a new radiator may not cure the problem if ur headgasket is leaking. best bet is to test this with that dye tester...its yellow and should turn blue if exhaust gasses are present in ur radiator system. don't waste ur money on something if the problem doesn't lie there. try to isolate it first, then go from there. i got a feeling on this, i hope i'm right but at the same time hoping for you that its not.

caldera has a point too, but oil in ur coolant... thats in the severe cases. aand at that point, ur headgasket already is gone and warpin things is just a matter of time. oil in coolant is a very bad sign at this point. but having exhaust gas in it is just as bad enough...

Well, first thing I'd suspect is the radiator cap, then check the bypass lines on the thermostat housing for blockages. Back flush the rad and coling system, and ut in some fresh antifreeze mix; only use a non-silicate HOAT antifreeze. Old fashioned silicate antifreezes tend to destroy the seals on japanese water pumps.