Many people have a lot of trepidation regarding cleaning their engine bay from fear of damaging engine components. Reality is most modern vehicles engines are very well protected & with a few simple precautions it is a very safe & easy detailing task.
The main reason most people clean their engine bay is cosmetic, but there are several other solid reasons to keep your engine clean. A very badly soiled engine can actually run hotter and keeping your engine bay clean can prevent corrosion as well.
In most modern cars, key electrical components and housings are tightly sealed. As long as you’re not directing a strong stream of water (or a pressure washer at close range) directly into these components, you should have no issues at all.
If you are working on a classic car or older model (mid-1990's or earlier) you should take extra precautions regarding electrical components. Try to use as little water as possible and make sure all exposed electrical components are covered.
Depending on your vehicle you may or not be able to see your alternator when you look into the engine bay. If you vehicle's alternator is exposed (if you can see it) cover it with either a plastic bag or tin foil. Tin foil is easy to mold and fit around the alternator without having to tightly secure it.
If you have an aftermarket intake system with an exposed air filter, cover it up with a plastic bag and secure it with a rubber band.
Although electrical components in newer vehicles are generally well covered and sealed just to be overly cautious avoid hitting visible electrical components with high pressure water at close range.
Do not detail your engine when it is hot.
What you need:
CLEANER: There are a number of great dedicated engine bay cleaners on the market (Sonax Engine Cleaner & Griot's Garage Engine Bay Cleaner are 2 great choices) but a good all purpose cleaner will also give you great results. If the engine has a lot of oil or grease buildup Griot's Garage Oil & Grease Cleaner is a great product for that.
BRUSH: Collapsible, bendable detailing brush. The brush will allow you to get into tight areas to agitate your cleaner. The 2 brushes below are great options. If you want to get really meticulous with your cleaning the SM Arnold 3 piece detailing brush set can come in handy as well.
TOWELS: For engine cleaning do not use any good quality towels. Any old towels you have will be fine.
On a cool engine you can either spray your cleaner directly on the dry surface or some detailers prefer to wet the engine before applying the cleaner. Giving the engine bay a quick rinse before applying your cleaner will get rid of any loose dust & dirt right away & if the engine is wet before applying your cleaner it can help save product. Spray the cleaner all over the engine bay (Don't forget to spray the raised hood as well).
Follow your cleaning products directions on how long to allow the cleaner to dwell.
Use your brush to agitate the cleaner and get into the tight areas.
4. Use an old towel to clean the flat areas and the raised hood.
5. Rinse the engine.
6. Dry the engine. If you have access to an air compressor, car dryer or leaf blower you can use any of those to remove any puddles of standing water. Use your towels to completely dry the engine bay.
7. Once the engine bay is dry look for any areas that are not totally clean and just spot clean those areas with some cleaner on a towel.
7. Once the engine bay is dry you are ready to apply your dressing. One benefit of using an aerosol type dressing is that you will get very even coverage. If using a trigger sprayer type dressing use a clean dry towel to distribute the dressing evenly over the surface.
That's it! Now your engine bay is looking great! Clean your engine about every 6 months to keep it looking like new!