then rip the radiator out and flush it ....... and with the head ive done those heaps takes at the most say about 1 1/2 on and off , and the headgasket is about ..k cant remember lol , but suounds like your headgasket aye take the radi cap off and run the thing , OR run the car from cold for 2 mins then take the cap off , if it pops off then well yea heagsket or cracked head