ound like the problem could be in 1 of many things first thing to do is check the thermostat is working you can do this by taking it out and placing it into a cup of boiling water if its ok then leave it out and check that the water is flowing around the engine by reconnecting all the pipes and running the engine look in the water bottle to check the flow is ok.
If that is ok then it could be engine temp sensor or olling fan problem.
Good luck.
Joe
March 2008