Safe and Effective Methods of Cleaning Your Engine Bay
When detailing an engine, it is important to use as little water was possible and avoid spraying in a single area for more than a second or two. While engine compartments have become more sophisticated (read: water resistant), there are always risks when introducing water to an electrical and mechanical compartment.
Given this, simply run the engine for 5-10 minutes with the hood closed, turn off and rinse the area with water (read disclaimer above). Following this, liberally spray an all purpose cleaner solution on everything. Use various brushes and a bucket of soapy solution to agitate all areas, then re-rinse the entire compartment.
Close the hood, run the engine for 10 minutes at idle and turn off. Dry everything off with towels, dress all plastic, rubber and vinyl with a water-based dressing such as Zaino Z16 or Armor All. Polish painted surfaces near the strut towers and on the bottom side of the hood. You can even protect it with a paint sealant to help repel dust and make subsequent cleaning as easy as wiping the area down.
As you can see, the after shots show a beautifully clean engine compartment that will show well and be much easier to maintain for the future.