i am having the exact same problems . while driving at speed my temp gauge goes up and fans stay on its driving me crazy too . so far i have replaced water pump thermostat radiator coolant cap all with no success the last thing i have to do is cht sensor and im praying it helps but no banking on it . i am also not loosing coolant and had a pressure test the results were 190 psi on cylinder 1-3 and 180 on cylinder 4 so i am not convinced it is head gasket a few suggestions that have been made to me are bottom radiator hose getting vacumed at speed and possible catalytic converter issues i was hoping you may have solved yours and had an answer lol

my car is also a 1.8 2001 zetec