GTA gone :( Punto
Sporting Cheap Fun
Join Date: Mar 2009
Location: United Kingdom
Its does sound like your thermostat is stuck open, a common problem, that is easily cured, its even a DIY job if you fancy it. It wont harm driving the car with it like that, but get it done sooner rather than later, as a stuck thermostat causes a significant reduction in your MPG, so it will pay for its self after a while, especially at todays fuel prices!
Not an expert on radiators letting go, if you are not losing water, then I would not be too concerned, but keep on eye on it. I would expect there to be warning signs of dampness at the botton of the rad if it was starting to go. Changing the coolant maybe a good idea as suggested earlier.
I hope that helps, i am not an expert but have read of number of these types of threads before.
147 Ducati Corse
MiTo 1.3 JDTM-2 (95) Lusso