I have a fiesta turbo which has just been rebuilt. But is running very hot but dont know why, I have replaced the radiator the thermostat the fan switch and the interior rad also had a water pump. The temperature does not seem to drop below 100 degrees c. So i checked the obvious the thermostat is opening and all of the pipes are getting hot. But i have noticed that when the thermostat is in there is not much flow back through the return pipe to the header tank. When it is out its much better and runs cooler and the fan cuts in and out, is it safe to run like this or will it cause problems.