i YouTube a bunch of videos as far as cleaning the engine bay and like bfleming mentioned most of the electronics is shielded or covered. i use my pressure washer real quick across the entire bay. i try not to get too much in the alternator. than use a leaf blower to blow all the water out than use CG's Natural Shine to detail all the plastic pieces. for you i would use an engine degreaser around the coolant area that you're talking about to get some of that sludge out. or you could use Purple Power. i wash the engine bay everytime i wash the car so pretty much every week and no problems after doing this for 3 years.
