My 2004 Honda Civic LX overheats at high speeds. I have replaced the thermostat twice and the shop says that the radiator is fine as well as the water pump. They cannot figure it out. It only happens at high speeds after driving for about 45 minutes. It will fluctuate between hot and cold and then will finally stay hot and I have to slow down or pull off before it gets to the red.
Thanks for any advice!!