Do not wash the motor. You can have it steam cleaned by a professional. If it is so grimy it needs cleaning, there are oil leaks attracting and holding grime. Fix the leaks after you clean the engine so yo can seem where it's leaking from.

That'd make it REAL easy to find a vacuum leak, since water would get "sucked in", instantly turn into a much larger volume of steam, and the crack your engine block RIGHT where the leak was, LOL!

I clean my engine y hand with a rag and some spray cleaner. Once you put the hose under the hood, shits going to go wrong one day.

I wash my engine all the time and I shut mine off just use air (pressurized) to blow off electrical system and wires. "Do not get CPU , EMC ect. wet"