99 punto radiator water boiling

hi,
little problem with punto S, hoping someone might be able to shead a bit of light on it.
when i start the car after around 5 minutes the water in the radiator pipes start to built up a lot of pressure and then the water starts boiling, and large amounts of steam come out along with water pushing itself out of the top of where you top up the water. i think it can be anyone of two things. but i do no its not the fan motor as in this weather a 5 minute journey it should not boil as i have driven it without a fan for over an hour before and still only warm.
1. the thermostat has gone. i am going to take the thermostat out tommorrow and run it without it to see if it stays cool. if it does ill leave it out.
2. the water pump has gone. not too sure about this one. but will try changing after trying the thermostat.

sorry for long winded one but any help would be great.
thanks

I think your thermostat has stuck shut. Is it just the top radiator hose that gets warm? That's what happened when a stat in a previous car failed in the shut position. The hose also swelled up due to the pressure.

thanks for the reply. Both the pipes are warming up yes and when i took it for a 5 minute drive arlier there is a lot of smoke coming out the exhaust constantly and it is using a lot of water. somthing makes me think it could be a head gasket.

any thoughts??