Tirebiter,
While I support your "let's debunk the urban myth" intent, at some level you have to say that both common sense and a basic understanding of physics suggest that taking certain risks are just not smart. As an example, lugging an engine is generally considered to be a bad thing to do (I'm assuming you'd be willing to take that as truth and not myth) and most of us would try not to lug our engines. That said, how many of us have ever had an engine hand grenade due to lugging? Probably none. Does that make it not true? I'm willing to support the theory that ether COULD ruin an engine and will refrain from using it. The satisfaction of proving the truth at the expense of destroying my engine is clearly not worth it. While I defer to your obviously greater knowledge and experience, I'd also suggest that it's possible you never saw this kind of damage because the next stop for these cars (the few there may have been) was the junkyard and not your shop.
Since I spoke to the cold water on a hot engine theory I'll address that. As a fan of very old cars I believe it is well beyond urban myth that many years ago engines could be damaged if the coolant in a hot engine was refilled rapidly with very cold water. Engines today are far better made so it is reasonable to assume that that problem may no longer exist. However, I can speak to one instance where a friend cracked his exhaust manifold when he went through a cold winter puddle too fast. Did the water crack it or was it mostly gone already? (I have to admit the car was a Lancia so the latter theory is very possible) It's hard to say for sure. One thing I do know is that there are a number of sensitive and precision parts on our cars that are expensive and I would prefer to treat them with some respect. If you want to volunteer, I'd be happy to accept the results of a test where you get your engine nice and hot then douse it with ice water to see what happens. Perhaps we can expel this urban myth once and for all.
