ok, to cut a long story short the engine seems to be running cold. The water pumps been changed as has the thermostat and the radiator switch. The cooling system has been flushed and the coolant renewed and i spent ages getting rid of airlocks. The reading comes up to normal after a VERY long time when the car is stationary but as soon as you drive it it cools right down until the temp. gauge practically reads zero. The temperature sensor itself was changed when I got the car about a year and a half ago, could this be the only possible explanation that it has went duff again?