Cooling system boiler over again

[Josh@Renparts]

mk2 ph2 1.4 16v. second time ive been sat in the car not moving with the engine running. Mate was in his car his fan kept coming on, mine didn't come on once. Then next thing i know there is steam coming out from under the bonnet. I assume its a dodgy thermostat or something? What part needs to be replaced?
thanks
josh

 

[16v_jon]

when you stood does your temp sensor go all the way to the top? is water getting into the rad? (test this by sqeezing the hoses near the rad and looking if the header tank level changes)
Test the fan is working by getting 2 bits of wire attaching them to the battery and to the fan connector