I changed my 3rd blown head gasket this week. This one on a 03 civic ex. I've changed one on a 01 civic ex last october, and one on a 03 civic ex last june. All had the same symptoms.

They lost heat at a stop light or at an idle. The coolant tank overflowed and spit all over the transmission. I also found when I used a hose from a compression tester and added 40psi of pressure from my air compressor i had bubbles come out of the radiator.

All the head gaskets blew in the same way. The black gasket material was eaten away and cylinder gasses leaked into the coolant system. I also noticed the spark plug for the bad cylinder was clean and white compared to the rest.

With the head off I noticed the valves were a rust color in the problem cylinder.

I hope my pictures display..........

 

Yep.... that tends to be how headgaskets blow...