B3 Water temp gone through the roof!

[mifkif]

It snowed again here today, so my usual 20 minute dash to work, took me an hour longer. When I was near to work I realised that the temp had gone right up to over 100, and the little red light was flashing.

I am not sure how long it had been flashing.

As a panick measure I popped the bonnet to aid extra airflow, as we cued in the traffic.

When I got to work I lifted the bonnet and carefully opened the expansion tank. It hissed but no steam.....

Tonight as soon as I started the car the temp went right up and the light started to flash. All the way home but interittantley, the light flashed.

Any ideas where to start to look. I am thinking it is some sort of temp sender somewhere.

All/any help appreciated.

Thanks,

Matt