Does and don't for a wash under the hood. I work near a quarry and hate the gray silt that covers my engine.

 

spray it down with simple green or any good degreaser, let it soak for a minute than hose it off with a garden hose. i avoid the intake, alternator and ECU thats in the firewall. be sure the engine is cool when you wash it.

 

I also use simple green, but I use a pressure washer. I hose everything down, except I blew the under hood decal off once, but the dealer got me another.

 

I use DP Engine Degreaser and a nylon brush. The cleaner is especially efficient and doesn't require a ton of product to be used to get excellent results. It is safe for use on plastics, rubber, metal, paint, and even clear coat.

I've never had a problem with spraying the engine down, however, do this at your own risk. Make sure the engine is cool and use a regular water hose. There are a lot of electrical components under the hood. These components were designed to survive in the harsh underhood environment, but I don't think they were designed to survive repeated blasts with a jet stream of water. Just use common sense and know what you're spraying. If in doubt, cover it up.

 

Any foaming engine degreaser will work wonders :)
make sure your engine is cool first

 

I did on my Grand Marquis with simple green and one of those garden veggy sprayers but found out I got some water under the plug connectors at the coil packs.
Thakns...