Not to get in Marcs way here, but it is dead dangerous to most motors to wash them when hot.... I don't think Marc is telling you that...
Wash it a little warm OK, but not after running hot, that can cause all kinds of very serious problems... Gaskets blown, exhaust manifolds cracking, and on conventional diesels even seizing up the injection pumps and such... Don't wash the engine hot... I spray on a little degreaser, when the engine is cold, and then hose off. My own engine is so clean I don't need to, but that is how I do it when I want to clean up a grubby engine. Just don't put cold water on a hot engine..
Best Regards, Lone Ranger...