I will be driving steadily along at say 60mph all is well. Then, suddenly, the STOP light flashes and the temperature gauge rises to the red zone, its like that for like a second and then returns back to normal. I then stop the car, there is nothing actually wrong (i.e. not overheating, water fine, oil fine). Turn the ignition off, restart and the car is back to normal.
Both of my previous Mk1 307s had this, and many other 307 owners have too. It IS the coolant temperature sensor.
You say you've had it replaced, but its possible the replacement was duff, or the wiring may be damaged.
Take another look. And also while you're in that part of the car, take out the battery and tray and give the earth points under it a good clean.
And do the same for the cooling fan relays under the plastics. between the engine and the grille.
And also if you've lost coolant when changing it you need to top up using the old pop bottle filler trick, and operate all three bleed screws to get air out of the system.
Edited by Gibbo_Wirral on 06/11/2018 at 12:35
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