Further, the anti-freeze solution reportedly can remove anodized colors. If you like the color anodized on your engine, you may do better with another source for cleaning it than the crock-pot method. Of course, if you simmer it too hot, that can make it worse...

Also, the fumes can be harmful to your health - if you do crock-pot an engine, make sure there's plenty of fresh air ventilation.

Final thought, mostly no longer a problem, but some earlier automotive engine anti-freeze mixtures were very bad for aluminum. Less problem today since so many car engines use plenty of aluminum exposed to the coolant...