cleaning engine bay with water from hose

How to Wash, Clean, and Detail Your Engine Bay

Maintaining the cleanliness of your engine and engine compartment is essential for several reasons. First, it helps to keep the engine running cooler. Heat is one of the primary enemies of your engine and drivetrain, so keeping it cool will help it last longer. Second, a clean engine is easier to diagnose when there are problems. If there is a leak or a broken component, it will be much easier to see and fix if the engine is clean. Finally, a clean engine simply looks better! It will make your car look more polished and well-maintained.

Unfortunately, the engine bay is also one of the most neglected parts of your car. Many people never clean their engine bay, and as a result, it can become a haven for dirt and grime. This can lead to corrosion and, ultimately, component failure.

Table of Contents

Engine Bay Cleaning and Detailing Techniques

There are two ways to properly clean a vehicle’s engine compartment. The first method is to wet wash the engine and engine bay. The second, is detailing the engine and engine bay. Both achieve similar results, but require different approaches.

Wet Washing

Wet washing an engine compartment is when all of the electrical and water-sensitive components are covered, followed by spraying the engine bay with an engine degreaser. After allowing the degreaser to thoroughly penetrate, the next step would be to agitate the degreaser with a brush. After brushing away all the loosened build-up and gunk, the engine bay then gets rinsed with either a pressure washer or a hose, typically one with a ‘shower’ setting.


Today, when you open the hood of a modern car, you will mostly see plastic covers and cladding with some body-matching paint on the inner portion of the fender and the underside of the hood, rather than the engine itself. For engines and engine compartments like this, you should use the detailing approach instead of the traditional wet wash approach. This involves spraying the engine compartment with an all-purpose cleaner, scrubbing it with a brush, wiping away the cleaner and any loosened dirt, dust, and grime, and then dressing all the plastic surfaces with a dressing.

In this how to clean an engine bay article, we’ll be covering the wet washing method. So, how do you clean your car’s engine bay?

Supplies Needed

  • Compressed air, to blow out debris
  • Masking tape, plastic bags, towels, or anything else that can be used to cover sensitive components
  • Cleaning brushes
  • Engine degreaser
  • Microfiber towels, both clean ones and ones suitable for dirty surfaces
  • Spray-on engine dressing
  • Pressure washer, hose, or water spray

Before Pictures

before cleaning dirty engine bay


before cleaning dirty engine bay


before cleaning dirty engine bay


before cleaning dirty engine bay

Step 1: Remove Debris

It is faster and more efficient to simply remove the large debris by hand and then use compressed air to blow out the remaining debris that accumulates under the hood, around the firewall, and wiper arms. Attempting to blast these things out with water will cause them to become wet and soggy, and they will fall into the engine compartment where they will still need to be removed. This can be done using a variety of methods, including a leaf blower, or professional-grade shop vacuum if available. After removing the large debris, blow out the tight, hard-to-reach areas to get the rest of whatever is left.

Step 2: Cover and Protect Sensitive and Electrical Components

Car manufacturers design engines and engine compartments to withstand water exposure, primarily from road spray during wet weather. Most electrical sensors and components are protected by plastic covers, cladding, or compression gaskets. However, it is always best to take extra precautions. Simply open the hood of your car and inspect closely for any components or areas that should not be exposed to water or cleaning chemicals. Cover these areas or components to keep them dry.

Pro Tip: If your vehicle’s battery is located in the engine compartment, it is highly suggested to disconnect it before starting the engine bay cleaning process.

Areas to Check and Protect

  • Intake openings
  • Distributor
  • Alternator
  • Coil packs
  • Sensors
  • ECU (Engine Control Unit)
  • Fuse box (if it isn't already covered)
  • Electrical relays (typically found in older cars)
  • Solenoids (typically found in older cars)
  • Alarm systems
  • Intake air filters (typically found on aftermarket systems)

What to Use

  • Microfiber towels
  • Plastic bags
  • Masking tape

Step 3: Cleaning Under the Hood

As with any car cleaning job, start from the top and work your way down. Spray an engine degreaser onto the painted portions on the underside of the hood. Take note to avoid getting degreaser on the insulation mat. Agitate the degreaser with high-quality brush. 3D Car Care detailing experts recommend dipping your brush into a solution of car wash soap before scrubbing. While doing this, it is a good idea to also clean all the plastic bits around the windshield wipers at the same time. After rinsing, wipe the painted sections of the hood dry using a clean microfiber towel dampened with water.

Step 4: Clean the Engine and the Engine Bay

Start by spraying an engine degreaser over the entirety of the engine and its surrounding area. Allow the degreaser to penetrate and work itself in for about 45 seconds to a minute. It’s important to not let the degreaser dry, however. Once the solution has worked itself in, begin agitating the engine and everything around it using a high-quality detailing brush. Don’t be afraid to use an assortment of different brush types to clean hard-to-reach areas. Finally, rinse the engine compartment down using your choice of water source.

Pro Tip: For engine compartments that are severely neglected and heavily soiled, it is advisable to divide the compartment into smaller, natural sections and only spray the cleaner on one section at a time. This will prevent the cleaner from drying in the other sections of the engine compartment while you are working on one section.

Step 5: Drying

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

Step 6: Remove Protection and Coverings

As mentioned in step 2, some engine components needed to be protected, masked, and covered in order to avoid any water damage. It is equally imperative to remove all plastic, tape, and other materials from the engine compartment before starting the engine. If you have placed microfiber towels in the air intakes to absorb or stop water from getting into the fuel induction system, remove them before starting the engine. After removing all tape, plastic bags, and other materials, use compressed air to dry these areas thoroughly. Finally, wipe the areas with a clean microfiber towel.

Step 7: Run the Engine

Once you are 100% sure that all tape, plastic, other coverings, and towels have been removed from the engine bay, start the engine to warm it up and finish the drying process. After starting the engine, check to make sure that there are no forgotten items that could cause problems, and then close the hood. By closing the hood, you will trap the engine heat in the engine compartment, which will speed up the drying process. Additionally, the engine cooling fan will circulate air in and around the engine and engine compartment, which will further assist in drying via evaporation. Run the engine for around 5 to 10 minutes.

Step 8: Engine Dressing and Detailing

To complete the project, finish up with detailing dressing on all the plastic bits and pieces, including the plastic engine cover if applicable. 3D Instant Shine, 3D Ultra Protectant, and 3D LVP Conditioner all work great and will get your engine looking brand new.

Step 9: Wrapping Up

Once the engine has been cleaned, washed, detailed, and dressed up it’s time to run the engine again one last time. Again, you want to run the car for around 5 to 10 minutes to burn off any of the excess dressing that may have gotten onto the metal pieces, such as the exhaust manifold, headers, etc.

After Pictures

after cleaning engine bay


after cleaning engine bay


after cleaning engine bay


after cleaning engine bay


The wet wash technique is the best option for cleaning the engine and engine compartment of severely neglected or older cars. It is helpful to have experience, but if you have never used this approach before, the only way to gain experience is to start. Let’s get detailing!

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