While a pressure washer would work just fine on the tough metal parts of your engine, there is a lot going on under your hood than just the engine itself. There are wires, hoses, clips, and other important parts that aren’t as strong and can be damaged by a pressure washer. Water is safe to use under your hood, but a pressure washer is too powerful. A simple garden hose works just fine for rinsing off an engine bay that has just been cleaned.