coolant can't evaporate
it's a sealed system

either you've got a leak, or you've blown the head gasket between the cooling channels and one of the cylinders.

EDIT - it's not a Fiat is it? If so, you've probably blown one of the coils and taken the ECU with it. Really common. You can GAZ me if you want any advice
( the mighty badger Aphrodite, on a bar stool, by your side, Fri 19 Jun 2009, 10:00, archived)

either that
or car AIDS
( WormuIus, Fri 19 Jun 2009, 10:02, archived)

sounds expensive :o( it's only a 51 plate too
Serves me right for buying a Clio I guess

EDIT: yeah cheers will send you a gaz
( h3donist tryin' to play me out as if my name is Sega.., Fri 19 Jun 2009, 10:04, archived)