Tips on Washing Your Engine
Aside from keeping the outside of your vehicle looking like brand new you also want to make sure you periodically clean the engine compartment. There are many reasons for doing this, including helping prevent rust, to check for oil or fluid leaks and to detect belt wear. To soften the grease and grunge that collects in the engine compartment you should start the engine and let it run for a few minutes and then shut it off. If you can just hold your hand on engine without burning, then it is warm enough to clean. The proper temperature for cleaning the engine is warm but not hot.
While the engine is cooling down you will want to cover the openings on the motor where you do not want water to get in. These include the air intake/air filter, the distributor, the coil and the oil dip stick/breather. You can use plastic baggies and rubber bands to cover the openings. You will also want to check the tightness of the oil filter cap, power steering cap, windshield washer fluid cap, battery filler caps and all other caps.
Now that you have the engine warm and everything is sealed, spray the engine and engine compartment with a high quality non petroleum based degreaser. Start at the bottom and work up, that way you won't be getting your face covered with degreaser.
Allow the degreaser to set for about three to five minutes and then use a 100% cotton towel or a soft brush to start removing the heavily soiled areas. Then, re-spray and re-brush any areas that need additional cleaning. Once the entire engine and engine compartment have been cleaned, rinse it thoroughly with water. You don't have to use a high pressure sprayer, a gentle spray will work just as well and you won't have to worry about getting water in any sensitive spots.
Once the engine compartment is clean you can remove the plastic bags and rubber bands. Then dry any puddles and aluminum parts with a soft towel, but use paper towels to thoroughly dry the battery. At this point, start the engine and allow it to warm up. This will dry the rest of the engine and will evaporate any moisture that has collected.
Once everything is dry and completely cooled you should wax the painted areas of the engine compartment, but not the engine. If the undercoated aluminum areas are dull or have white corrosion, use a mild metal polish to help restore the finish. At this time check the battery terminals to make sure they are clean. If they are not clean you can disconnect the cables and clean both the cable terminals and the battery posts with a wire brush.
Next, check all hinges, throttle cables and shocks to see if they need a thin coating of non silicone lubricant. Finally, check all fluid levels and remove any stray baggies and you have completed cleaning your engine.