Rule 308 is right, there is a condition where the headgasket is "slightly" blown.

Here's what I did to check:

First start of the day, engine dead cold.
Open the hood and take off the coolant reservior cap. Set it aside.

Get in and prepare to start. First, however, position yourself to where you can see the open coolant reservior. Start the engine. If coolant (assuming it is at the correct level) wells up and overflows, the head gasket is failing. Be aware that this is like being a little bit pregnant.

With a cold engine, a small gap at the gasket can allow compression pressure to get into the cooling system. As the engine heats up that gap may become closed up. The gap will continue to worsen.

Good Luck,

Bob

:>)