[mr0077]

And test the coolant for combustion byproducts...a radiator shop can do it for you, I'm not sure if there is a kit (like test strips) available at an auto parts house. That would eliminate the head gasket.
Reason I'm thinking head gasket is, when combustion gases get blown into the radiator, it will heat up fast. Another way to check for this is to let the motor idle with the radiator cap off...if combustion gas is getting into the cooling system it will burp gas bubbles.