[expatpat]

We're talking about 2 different things. The cracked block et al are due the water cooling only one part of the block, which sets up large stresses from differential thermal expansion/contraction.

The boiler issue, OTOH, is due to the expansion of water when it undergoes a phase change from liquid to vapor -- pipes bursting due to freezing in the winter is much the same thing, except that here the phase transition is to the solid state.

[blackdog]

Water to ice however does not generate a 1,600 times increase in volume like water to steam does.