My son has a Honda Civic where the engine keeps wanting to overheat. There are no fluid leaks, and we replaced the thermostat. It keeps “blowing” the cap on the overflow.
The fan seems to be working fine, so I don’t think that is it. Once it warms up, if you squeeze the hose from the top of the radiator, it is not seem to be pushing much water through (water pump??). You cannot see into the radiator (to check for air bubbles), but popping the overflow cap makes me wonder if it the head gasket has blown, and we are getting exhaust into the coolant system.
Could be a bad water pump or clogged up cooling system. Check the manual to see if it is time for a timing belt water pump replacement. It may not have a belt. A timing belt breaking in some engines can ruin the engine, and typically timing belt and water pump are replaced at the same time.
It does have a timing belt, and we don’t know when it was last replaced. We were already planning to replace it and the water pump this summer, given it is an interference engine…