Hi and thank you in advance, I have a 2005 honda civic ex, everything stock. My engine temperature gauge has been fluctuating, mostly in city, on highway it stays in the middle range. Here is what I already did. 1.) Changed the thermostat, burped it. 2.) Changed the radiator cap, burped it. This worked for a while. 3.) Checked for leaks, but did not find anything.
After driving the fluid escapes from the radiator and the overflow tank overfills.
After letting it cool, when I open the radiator cap there is lots of air/pressure build up and while I open the cap the fluid gushes out of the overflow tank cap.
When I fill up the radiator the gauge stays normal for about a week of driving and after that it starts fluctuating again.
What would be the next logical thing to check? Radiator/headgasket. Or should I bring it to a mechanic at this point.