Hi guys its running a 4x4 saff cossie, stage 3 head, camed etc loads of other bits buuuuuuuuuuuut... a standard ic

Ive only got a standard fan on the rad which ive put on a switch. The car has never done this before till it over heated once a couple of weeks ago and burst a water hose which i replaced so i think it may be an air lock. How would i go about sorting it out ?
btw ad4m rst i saw your car last night mate its fucking amazing !!! I was the white s2 with polished roll cage parked infront to the left of you.
Cheers
Sam