Why do cylinder heads crack?

[CompOrangeFox]

Just a general question and what damage does it do to the engine?

[StangerJon]

the heat expansion that they endure over the course of running, then cooling when turned off.

atleast thats what I think.

the damage is coolent leak, and possibly a loss of compression. (depending on the size of crack. and location.

[CompOrangeFox]

So if one were to buy a vehicle with a cracked head is this vehicle prone to more cracked heads or is it something that just happens? And once the coolant gets into oil does this damage any of the other engine internals?

[MINNESOTA 5.0]

coolant in the oil will wipe out the bearings.
if the oil looks like a milkshake, plan on tearing the engine down to inspect/rebuild.

alot of people will just change the oil and drive it, but if it has been run already with coolant in it, it will be trouble.

heads on some engine/makes are prone to cracking. some just do it once and never again.

what kind of car are we talking about? engine?
that would help alot for common problems with it.

[Fernanernie]

If you have the head(s)repaired, make sure you have it(them) decked too. No sense putting on a head that's warped