Re: how to clean engine bay?
For the longest time I took my car once a year to the car wash, use the power washer and lightly sprayed the engine compartment with the engine degreaser. Only on sturdy metal parts minus the engine did I get the nozzle close. I also made sure the engine was just warm and not hot. After soaking a few minutes I lightly rinsed it off with water while not using the high pressure setting.
I look at the engine compartment as it's not water proof, but water resistant. A little understanding of the engine components and common sense will go a long way.