Wet Wash Engine Detailing – How to Clean and Detail your Engine Compartment – 9 Easy Steps | 3D Car Care

Clean engines run cooler and are easier to diagnose when there’s problems

Keeping your engine and engine compartment clean is important because it helps to keep the engine and engine compartment cooler as heat is one of the top enemies to your engine and drivetrain.  Keeping the engine and engine compartment clean also helps to identify and locate problems like leaks or broken components simply because it’s easier to see problems when the engine is clean versus covered in a layer of oily grime and sludge.

Wet Wash Engine Detail versus Cosmetic Engine Detail

There are two different ways to clean and engine and engine compartment.

Wet Wash Engine Detailing

This is where after covering and protecting all the electrical and water sensitive components, you’ll spray in an engine degreaser, allow it to penetrate, then agitate with a variety of brushes and the spray the engine and engine compartment down with either a pressure washer or a water sprayer and water hose.

Cosmetic Engine Detailing

Now days when you open the hood of a modern car for the most part you don’t see the engine, just gobs of plastic covers and cladding with some body matching paint for the inner portion of the fender and the underneath of the hood.  For engines and engine compartments like this instead of using the traditional wet wash approach you use the cosmetic approach, which is to simply spray the engine compartment down with an all-purpose-cleaner, agitate with a brush, wipe-off the cleaner and all the dirt, dust and grime that’s been loosened and then dress all the plastic surface with a dressing.

This article will cover Wet Wash Engine Detailing.

Supplies needed

  • Compressed air to blow out debris
  • Masking tape, plastic bags, microfiber towels, kitchen plastic wrap aluminum tinfoil
  • An assortment of quality cleaning brushes to scrub various components and surfaces.
  • Engine degreaser
  • Microfiber towels suitable for dirty work.
  • Spray on dressing for plastic, rubber, and vinyl
  • Water hose and sprayer with shower setting
  • Optional – Gas or Electric Pressure washer
  • Microfiber towels for drying engine compartment

Pressure Washer versus Water Hose and Water Sprayer

Before we get to the step-by-step instructions, first a comment about pressure washers versus a normal water hose and simple garden water sprayer.  Using the Wet Wash technique works best for really dirty, oily, grimy engines and engine compartment that have been neglected and are in dire need of a strong engine degreaser to restore the factory new appearance.  

While a pressure washer is a great tool in the hands of an experienced professional, the approach shared in this article is to use a water sprayer with a SHOWER setting available at most hardware stores.  The reason why is because with the shower setting, you’re never FORCING water into places you don’t want water like is possible with a high-power pressure washer.  

The key to getting an engine and engine compartment clean without a pressure washer comes from using a high quality, super safe degreaser like 3D Grand Blast.  Then instead of using the combination of the degreaser and high-pressure water spray to clean the engine compartment – you use a brush with old fashioned elbow grease to AGITATE the degreaser and thus you don’t need high pressure spray of water you only need a soft, gentle shower spray of water to do the job and do it without risking any damage to electrical components.  Make sense?

It's your choice but my recommendation based upon years of experience, if you’re new to engine detailing, start out using the safe approach of using an everyday garden water sprayer with a shower setting.  With a quality degreaser and an assortment of quality brushes and a little muscle behind the brush – you can loosen all the oily grime and sludge via the degreaser and agitation enabling the shower setting on the spray to simply rinse the engine clean.  No risk, super safe and for the most part just as fast and just as effective.

Step 1:  Blow out all leaves, sticks, pine needles, dead bugs, loose dirt, and debris.

It’s faster and more efficient to use compressed air to simply blow out all the junk that accumulates under the hood around the firewall and wiper arms.  Trying to blast these things out with water tends to get them wet and soggy and fall into the engine compartment where you’ll still have to remove them.  You can do this using a variety of ways including using a leaf blower, a MetroVac Blaster Sidekick and some Wet/Dry Shop Vac have the option to blow air by switching the hose attachment from extraction to blowing.

Step 2: Cover and protect any water sensitive components

Car manufacturers design the engine and the engine compartment to get wet without problems, this is primarily from water on the road when driving in rainy weather that splashes up into the engine compartment.  

Most electrical sensors and components are either protected by plastic covers or cladding and/or have compression gaskets in-between electrical connections.  That said, an ounce of protection is worth a pound of cure.  Simply open the hood of your car and inspect closely for any components or areas that common sense tells you shouldn’t be flooded with water or cleaning chemicals and cover these areas or components to keep them from getting wet.

Here's some examples of common components and areas to cover and protect.

  • Fresh intake openings – Stuff a microfiber towel into the opening then cover with plastic.
  • Distributor
  • Alternator
  • Coil Packs
  • Sensors
  • ECU – Engine Control Unit
  • Fuse Box if not already sealed in compartment
  • Electrical relays – older cars
  • Solenoids – older cars
  • Alarm systems
  • Exposed aftermarket air filters

To cover these areas, you can use a combination of:

  • Plastic bags like from convenience stores
  • Masking tape
  • Microfiber towels
  • Any type of plastic film like Saran wrap
  • Tinfoil – as long as the tin foil is not touching any open electrical parts

Professional Technique Tip

When cleaning the engine bay, it’s possible to get the engine degreaser onto the outside of the body panels surrounding the engine bay like the fenders and doors.  A quality degreaser shouldn’t cause any problems but if you want to take extra precautions to avoid any possible staining of the paint you can do one of two things.

1: Mix up some car wash soap and water and lather this solution onto nearby body panels.  By keeping these adjacent body panels wet with car wash solution any degreaser that lands on these panels will be diluted and thus prevent staining.

2: Use a painter’s plastic drop cloth and cover these panels before you start while everything is still dry so masking tape can stick to the car.

Step 3: Clean the underneath of the hood first

Always start at the top and work your way down.  Spray 3D Grand Blast onto the painted portions of the underneath of the hood.  Careful to avoid getting any on the insulation mat.  Agitate the degreaser with a quality brush and then rinse.  After rinsing, wipe the painted sections dry using a microfiber towel dampened with water.

Common mistakes to avoid

One of the most common mistakes people make when they are new to cleaning the engine compartment is to clean the engine first and then as an afterthought, clean the underneath of the hood.  The problem with this is if you clean the underneath of the hood first after cleaning the engine and engine compartment, you will have dirty engine degreaser and all the grime it dissolves and removes dripping down onto your clean engine.  If you’re going to clean the underneath of the hood, start here first, not after you’ve cleaned and rinsed the engine and engine compartment.

Unique design features common to the underneath of a car hoods

Color matching paint on the underneath of the hood

The perimeter of the underneath of the hood is often painted with the same color of paint as the exterior of the car.  These painted portions often have a film of oily grime covering them.  This grime is easily removed by spraying your engine degreaser onto these areas, agitating with a brush, and then rinsing.

Sound deadening and heat absorbing insulation

The center potion of the underneath side of the hood often times has a fiber insulation material to trap heat below the hood and absorb and engine and road noise to make your ride more quiet.  This material is easily torn and ripped if you get it wet with water and then scrub it with some type of brush.  To prevent damaging this material it’s best to avoid getting it wet and do not spray degreaser onto it and then scrub with a brush.  Instead, dampen a clean microfiber towel and gently dab and wipe to remove any surface dirt and dust.

Professional Technique Tip

For larger cars and longer hood, it can be too far of a reach to get to the painted sections of the back of the hood with short, handled brushes.  This is where a wheel well brush with its longer handle comes in real handy.

After agitating the degreaser and before it can dry, use the shower setting of your water sprayer to rinse the degreaser and all the oily grime it has loosened off of the inside of the hood.  This dirty rinse water will be falling down onto the engine and engine compartment, but this is okay because you’re going to be cleaning this area next.  

Wipe dry the painted sections of the underneath of the hood with clean microfiber towels and at the same time, gently wipe the insulation mat with a water-dampened, clean microfiber towel.  Later if you like, you can come back and use a surface protectant like 3D Bead It Up on the painted portions to create shine while adding protection and making future cleaning faster and easier.

Step 4:  Clean the engine and engine compartment

Spray 3D Grand Blast over the entire engine and surrounding area inside the engine compartment and allow the degreaser to penetrate and work for 45 seconds to a minute.  Don’t let the degreaser dry.  Agitate the engine and everything in the engine compartment using a variety of brushes that best fit the shape of the component you want to clean.

Professional Technique Tip

For engine compartments that are severely neglected and heavily soiled, divide up the engine compartment into smaller, natural sections and only spray the cleaner and work one section at a time.  This way while you’re working in one section you won’t have cleaner drying in the other sections of the engine compartment.

After agitating the degreaser, using the shower setting on your water sprayer, rinse the engine and engine compartment to remove all the degreaser and with it all the oily, dirty grime it has loosened.

Step 5: Dry the engine and engine compartment

Starting with compressed air, blow out all electrical connections, any areas or components that are covered and taped-off.  Also blow out any areas that will be hard to reach by hand with a microfiber towel.  After blowing out as much rinse water as possible, next hand dry the engine and engine compartment using clean, wheel and tire microfiber towels.

Step 6:  Remove any plastic covering, towels and/or tape.

It’s vitally important to remove any plastic, tape and then re-dry these areas with compressed air.  Also, if you place any microfiber towels into air intakes to absorb or stop water from getting into the fuel induction system – REMOVE THESE ITEMS BEFORE STARTING THE ENGINE.  After removing any tape or plastic bags, or other things used to cover and protect various components or electrical connections, take a few minutes to re-dry these areas with compressed air first followed by wiping with a clean microfiber towel.

Step 7: Start the engine and run for 5-10 minutes

Once your 100% sure all tape, plastic, other coverings, and towels are removed out of the engine bay, start the engine to warm it up and finish the drying process.  After starting the engine, look to see and make sure there are no forgot items causing problems and then close the hood.  By closing the hood you’ll trap the engine heat into the engine compartment to speed up the drying process plus the engine cooling fan will circulate air in and around the engine and engine compartment to further assist in drying via evaporation.

Step 8: Dress the engine compartment to restore a factory new appearance.

For all the plastic, vinyl and rubber surfaces use 3D Instant Shine or 3D Ultra Protectant or 3D LVP Conditioner.

3D Instant Shine is an aerosol spray-on dressing and because it’s an aerosol, it makes it easy to spray the dressing into areas that would be hard to reach as the dressing is aerosolized and pressurized.

3D Ultra Protectant is a pump spray dressing that works great on just about any surface and material.  After spraying the engine compartment down, use a clean, soft brush to spread the dressing and work it into hard-to-reach areas like corrugated housings, intricate areas, etc.

3D LVP Conditioner is a liquid dressing with a skin lotion-like consistency and can be applied using a foam or microfiber applicator pad and then worked in using a clean brush.

After applying your choice of dressing and working over the engine and engine compartment, using some clean microfiber towels, thoroughly wipe down the engine and engine compartment to remove any excess dressing.


Apply 3D Bead It Up to painted sections in the engine compartment.

For any painted section of the engine compartment, you can apply the 3D Bead It Up to add shine and protection while making future cleaning faster and easier.

Professional Technique Tip

After wiping down the engine as best as you can with microfiber towels, use compressed air to blow out any intricate hard to reach areas and/or electrical connectors and after blowing these areas out, if needed, re-wipe for a uniform appearance.

Step 9:  Close hood and run engine a second time

After applying the dressing and wiping and blowing out the engine and engine compartment, restart and run the engine again for 5-10 minutes to burn off any dressing that landed on the exhaust manifold or headers.


Using the wet wash technique for cleaning an engine and engine compartment is the best option for severely neglected and older cars.  It helps to have experience but if you have never used this approach then the only way to get experience is to take the first step and start.

The most important thing it to look for, cover and protect anything electrical or any fresh air intake for the fuel system.  Some vehicles have a fresh air intake, usually in the front of the engine compartment and sometimes these are openly exposed. 

If you discover this type of exposed air intake for the vehicle you’re working detailing, what I like to do is stuff a microfiber towel into the opening and then cover the opening by covering it with plastic and tape.  If by chance any water gets past the plastic and tape, the microfiber towel will absorb it, preventing the water from getting into the fuel delivery system.  The key is to remember to remove the towel before starting the engine.  As a reminder and a safety measure – I tape a note on the steering wheel that reads,

Remove towel from air intake

And just like that, problem solved, no risk involved.  Take your time, use common sense and if you need any help at all, reach out to me via email or phone and always happy to help others with their detailing projects.


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