Hi lads iv just bought a ka for my mum an it was missing a core plug so iv replaced it an no leakes all was fine then it pressured up in the header tank so i tried to bleed it but no joy so iv done the headgasket an it still the same it just bubbling up could it be the water pump iv no idea now bin at it allday thanks.

 

when you replaced the gasket did you get the head skimmed. Maybe a cracked block or something similar