This is a 2003 Honda Civic with about 140k on it.

I've had this car checked out by a mechianic and the thermostat was replaced had a pressure test to check for air pockets, nothing. Had a test for a bad head gasket with some sort of chemical test which came back negative. But the car still overheats. I was told by this mechanic that there is a pinhole-sized leak in the head gasket somewhere that leaks into the engine very slowly.

I have to drive about 60mi every day and as I drive at high speeds the car is fine it doesn't overheat. It's only when I am at idle or driving slowly that the gauge begins the rise. On these daily trips I have the heater blowing the entire time because I know it acts like another fan to take heat off the engine. But when I am at a red light all the sudden the air which is on the hot position will turn cold and then the gauge will start to climb. Is this normal for a blown head gasket? or when the coolant gets low. By the time I get to my destination is the coolant is basically gone and it's about the same time I am close to my destination that the air turns from hot to cold and overheats.

Also, this more after my 60mi drive it overheated and I looked under the hood and saw that coolant was sprayed all over the air intake and downwards below of the overflow could the overflow be spitting all the antifreeze out?

Thank you

  • How is your coolant cap? What is the pressure rating on it?
    – Zaid
    Jan 28 '15 at 15:04
  • The radiator cap? It's brand new nothing wrong with it.
    – AppleFix88
    Jan 28 '15 at 21:14