Temperature light came on whilst driving

[Rio and me]

I have not had my passat 95 1.8 petrol long, and noticed (from memory) the temp stayed at roughly 70 ? and this morning it shot up to 110 and the light started flashing, i let it cool at home and the water level seemed ok but i topped it up a bit with coolant. if it does it again what could be the problem?
thanks

[HorseOffaGypsy]

The coolant is not circulating round the engine (most probably). The easiest thing to check is that the water pump drive belt is still intact and in place (this possibly also drives the alternator so it its gone, the battery light would have also come on).

It this is there and OK then other reasons for a blockage of some description need investigating... a thermostat blocked shut, a clagged up radiator, ice (if you had a very cold night and you've no antifreeze...)

If there are no blockages other things could included - faulty water pump, thermo-switch for fan faulty (you didn't say but I'm assuming you weren't stuck in heavy traffic or towing a caravan up a mountain!!) or even a faulty gauge or gauge sender (i.e. it not over heating at all!)

You're right about 70° being the "normal" position - you need to get it back there too! Overheating can cause the cylinder head to distort which is a major rebuild job! Don't go driving round unnecessarily.