If it is boiling then it would still be boiling after you pop your hood, engine bay temps aren't going to cool off that quickly. I never saw my meth boil and I live in an area that was seeing ambient temps in excess of 110F. I guess it is possible but I'm sure it would pop the top off the windshield washer tank that the meth is in. If it was boiling pressure inside would be rising much faster than it would be able to escape around the cap. This is the same principle as a whistling tea pot; water boils, builds pressure, and comes out the oriface in the top making the wistle sound.