I think there is air trapped in the system.it is running at around 80c untill you crack on the gass when you run at about 100mph for a mile or 2 the temp goes up to around 110c. If you slow down the temp falls to aroung 80/90c
the fans are working and there is new coolant in there (topped it up last week after water leak)
so i am at a loss really?
coould it be the termostat?