OT: I did my good deed for the day.

Sounds like a blown head gasket, BTW.

WHAT? 250 degress is 250 degrees. How can 250 degrees be much hotter that 250 degrees?

When superheated water in a cooling system is depressurized, the water has to change state from liquid to water. It does this by rapidly absorbing heat from the surrounding material. When the resulting steam comes in contact with your skin, it changes state again back to water, releasing the energy it picked up when it turned to steam. This energy is what causes steam burns to be so severe.

I'll try to explain this...bear with me a little.

When water is heated in an open system, such as a pot on the stove, the temperature rises up to around 212 deg F. At that point any additional energy input to the water converts water to steam (which takes ~5X the amount of energy required to raise the temperature of water from 32 deg F (but still liquid) to 212 deg F (but still liquid).

HOWEVER, because the engine cooling system is pressurized, the temperature of the liquid water can be increased above the natural boiling temperature. When the pressure is released, some of the energy of that pressure is used to convert the liquid water to steam. When the steam condenses on an object (such as that young lady's arm) the steam/water "gives back" that energy very rapidly! That 5X energy required to convert liquid to steam is what makes a steam burn so much worse than a liquid burn.

I think MarkB_MI is using temperature as a proxy for energy - since we can physically measure temperature, but can't quite come up with an "energy gage".

I'll be glad to go into more detail is you would like,...but I don't want to get too nerdy! (grin)

Nathaniel