hi folks.....only got my mk1 leon cupra 2 weeks ago and noticed water boiling in reservoir !!!,now i know the worst case scenario ...but its not over heating and blows hot air int car, previous owner had an empty bottle of rad weld in boot and i mentioned this but thot ok maybe just needs new radiator etc....its not losing water so cld it just b thermostat or radiator cap faulty ??,its a 52 reg with 140k ,plz help guys ....