I don't think that is right at all. I had several different cars/engine types over the years and I have never seen this effect. I think you thermostat is faulty.rainbowcar said:then the temp guage will just pass the second line on the guage (the one between cold and normal) then next time i look it has gone down!?
Unless you have a completely old fashioned thermostat fitted, they are supposed to be a two stage device. That way it slowly bleeds the cold water from the radiator into the closed system. This is to hold normal temperature and prevent thermal shock. The way it is working at the moment sounds like the first stage is jammed so its flooding the cold water straight in.