i dont know what all of you are on about, engine bay in any case should not be washed with water let alone with a pressure water......use a clean damp cloth and see it doing wonders followed by engine dresser of any good brand.....please DO NOT wash it with water.....specially from the pump wash service.
also by if you have been lucky so far does not mean the water washing wont ruin your stuff.....this theory is same as mein bohat red signal torta hoon aj tak masla nahi hoaa....
masla ik he dafa hona hai aur phir Pathetic PKDM quality ki posts lag rahi hon gi har jaga 
anyhow.....clean damp cloth do wonders 
dont mean any offence to anyone whatsoever