How To Clean Your Car’s Engine Bay The Right Way

We may receive a commission on purchases made from links.

We can’t blame you for selecting the DIY route in cleaning the engine bay. Professional work can cost $100 to $400, which is quite a chunk of change for something you can do in your driveway or garage. But as with most things related to car cleaning and detailing, there are things that you shouldn’t do when washing, and you don’t need to be an expert to wax the finish to perfection and keep it protected all year long. It’s essentially the same when cleaning the engine bay: There are things worth knowing to do it right, and you can expertly do so without spending big money on expensive cleaning products.

The engine bay of a modern car, or even older models equipped with OBDII computers is home to an array of electrical wires and components that don’t mesh well with water. Underhood parts, such as engine sensors, the alternator, ignition coils, or the distributor, could malfunction or break down inadvertently if left soaking in water.

Don’t get us wrong, though, since it’s relatively fine for the engine bay to get wet from time to time. However, enthusiastic DIYers could accidentally flood the engine bay with a strong stream of water, such as when using a pressure washer or garden hose at full force. Doing this without heeding the necessary precautions may cause a no-start condition after washing or cause unnecessary wear on hoses and other plastic parts.

The right way to clean an engine is to start with one that is cool to the touch. Never wash a hot engine, allow it to cool for at least two to three hours. If the engine bay is warm, open the hood and keep it open to facilitate the cooling process. In addition, ensure the transmission is in Neutral (N) or Park (P) and engage the parking brake. You don’t want the car rolling forward or backward accidentally while working under the hood, especially if the vehicle is on a slope or inclined driveway. Furthermore, it’s best to remove the battery or to disconnect the negative terminal whenever convenient to prevent shorts.

While the engine is cooling down, that’s the best time to rid the engine bay of leaves, pine needles, seeds, dust, and other debris. Remove by hand, or grab a vacuum cleaner to suck out all loose dirt and contaminants around the engine bay, particularly near the bottom of the windshield, on the plastic engine cover (if so equipped), and around the firewall. The gist is to remove as much loose dirt as possible.

When the engine cools, you can begin covering the parts with a large plastic bag. Lay a plastic cover over the entire engine, and you should do the same with the alternator and CPUs (if applicable) by wrapping them in plastic, in order to protect those parts from water splashes when cleaning the underside of the hood. When we say underside, we mean the non-shiny part of the hood that typically receives the most neglect.

However, washing the bottom of the hood is only necessary if it doesn’t have a foam insulating panel. Otherwise, you’re better off just wiping the sides clean with a damp cloth. If the panel is extremely dirty, damaged, or is beginning to warp or fall apart, it’s better to remove it altogether and replace it with a new one. But if the insulator panel is fine, don’t wet it with water.

You’re now ready to proceed to the actual washing part of the engine bay. Begin by rinsing or wetting all surfaces with a light spray of water to remove standing dirt while consciously avoiding the parts covered in plastic. You can use a hose or pressure washer while doing this, but make sure to do so at the lowest or lightest possible setting.

Washing is the most fun step. The safest and most economical way is to use a pump sprayer such as the Chemical Guys Mr. Sprayer, filled with ordinary car shampoo and water, to dispense the cleaning solution more efficiently. The best car wash soaps are mild on paint, rubber, and plastic, yet it has the necessary cleaning power to lift off grime, dust, and dirt. Spray some cleaning foam and gently agitate the surface with a cleaning brush, sponge, or old microfiber towel, working on one area at a time. You may need a toothbrush or a dedicated cleaning brush for hard-to-reach places.

Once done, grab the hose and pressure washer and give everything a final rinse using a fine mist or light water pressure. At this point, more than half of the dirty work is over, but you’ll still need to clean what’s hiding under the plastic covers.

Those plastic covers that you installed before cleaning? Now is the time to remove them. Grab some cleaning wipes to begin wiping the engine cover, the valve covers, and any areas with grime, sludge, or dirt. If the engine is filthy, grab your pump sprayer and give it a blast of foam before wiping it clean. In some cases, you may need a stronger cleaner, such as the CRC Heavy-Duty Pro-Strength Degreaser, to break down thicker slabs of dirt, sludge, and grime.

Drying is necessary after washing, cleaning, and degreasing. Use a separate cloth or microfiber towel to wipe all areas dry. The night-and-day difference of a dirty or clean engine bay would be pretty evident at this point, and you can essentially close the hood, pop open some brewskies, and call it a day. However, the final detailing step will make the difference between a clean and a professionally cleaned engine.

The absolute final, yet optional step to cleaning your car’s engine is to apply a restorer to all the plastic and rubber parts under the hood. Products like the Car Guys Plastic Restorer and Meguiar’s Ultimate Black Plastic Restorer are economical, easy to use, provide a like-new appearance, and offer a layer of protection against heat and wear.

Pour a small amount of the product on a foam applicator and wipe over the plastic and rubber parts, including the plastic engine cover, hoses, and other trim. Allow to dwell for about 10 minutes before giving everything a final wipe with a clean towel. This optional step will make your engine bay stand out and give it a professionally detailed look.

The excellent news is you don’t need to clean the engine bay every time you wash the car. Once or twice a year is sufficient, but wiping everything down occasionally with a damp towel will help keep it looking clean in between the changing seasons.