Use a pump-type garden sprayer and a STRONG solution of Trisodium Phosphate (concrete cleaner) Soak things down under the hood, let it sit for a few minutes and hit it with a high-pressure nozzle on a hose. Repeat as necessary.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!