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How to Clean Under the Hood of a Car? – 9 Detailed Steps

Written by Howell Crist / Fact checked by Sam Howard

FAQs

how to clean under the hood of a car

“It is necessary to wash under the hood of my car?” This is a common concern that most car owners raise. Not only do they not know how to clean under the hood of a car, but they’re also quite hesitant to do so.

After all, the engine bay contains wires, constructs, and mechanisms that can look far too complex for the average consumer.

But although you can get the entirety of your car cleaned at the carwash, including under the hood – it’s still better to know how to do it yourself. We’ll break the process down in detail.

What to Prepare

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  • Plastic bags
  • Tape
  • Toolbox (for removing battery cables and air intake filters)
  • Leaf blower or air compressor
  • Pressure washer or hose
  • Degreaser Spray
  • Stiff-bristled scrub brush
  • Dry rags, microfiber towels, and/or chamois

9 Steps to Clean Under the Hood of a Car

Step 1: Engine Prep: Cool Down

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Before cleaning under the hood, be sure your engine’s cooled down. Do not spray water under the hood while the engine is still hot!

Aside from the obvious risk of burns (to your person), sudden temperature variations can shatter parts of the engine or damage it as a whole. So if you just turned the engine off, wait a couple of hours.

Some experts recommend cleaning the engine while it’s still a little warm to help loosen the oil and grime build-up. However, it’s still too risky a step for beginners. For the sake of safety, always start with a completely cooled engine.

Step 2: Engine Prep: Cover Up

Once the engine has cooled down, cover vulnerable parts inside the hood of a car with plastic bags and tape. This will keep them safe and dry during the actual cleaning process.

Parts like the air intake, the alternator, exposed wires, electronics, sensors, the distributor cap, the fuse box, and other similarly susceptible areas should be protected.

Even if you choose to wash the engine without water, most Autocare and cleansing products that you’ll be using will leave moisture behind. It’s always best to err on caution when something as important as the car engine is involved!

Step 3: Remove Battery Cable & Filters

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Once you’ve secured all the exposed electrical parts, you’ll need to take out the air intake filter, the cabin air filter, and the battery cables. These three specific pieces are incredibly vulnerable, so spraying water under the hood while they’re still installed is too risky–even with a plastic covering.

After you’ve taken out both air filters, don’t forget to cover the exposed intakes with a plastic bag and tape.

Then, focus on taking out the battery cables.

If you’re confident you won’t let any of the cables – especially the positive cable – touch any metal car part, do it yourself.

If you aren’t comfortable with your skill, ask a professional or friend (who knows how it’s done) to help you.

Step 4: Clean Out Large & Loose Debris

The last thing you need to remove from the engine bay is large, loose debris. Dead leaves can easily get sucked into car engines, but even small pieces of rubble, twigs, and grass can find themselves all up in the fenders and grille.

If you can see them but can’t reach them, use a leaf blower or air compressor to clear them out. Be sure to hit the area below the windshield and surrounding the hood, too.

Step 5: Degrease Engine with Degreaser Spray

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If you want to use as little water as possible to wash your engine, a degreaser makes an excellent under the hood cleaner. Simply spray liberal amounts all over the engine bay, paying extra attention to the tougher, oilier areas prone to grease and grime buildup.

Try to avoid spraying uncovered electronics and gaps where the degreaser can drip, though.

If the engine is in serious need of cleaning, let the degreaser soak for 20 minutes. This will give it time to penetrate and break down tough oil and grease.

For regular cleaning, 10 minutes should be enough.

(Optional) Step 6: Scrub the Engine to Break Down Oil Buildup

If the engine’s not too dirty, some experts agree that scrubbing won’t be necessary. But if you need to let the degreaser sit for 20 minutes, chances are the engine bay needs a good scrub.

Use a stiff-bristled brush for stubborn, caked-on dirt. Alternatively, use a rag to rub off the grease and dirt. Make sure you’ve loosened and broken down as much grime as possible for rinsing it all off.

Step 7: Rinse Degreaser Off Thoroughly

Use a hose or power washer to rinse off the grease fully. Keep in mind that power washing should only be done on a light setting, or else you risk damaging the sensitive parts under the hood. You also don’t want to flood the engine bay.

If this is just routine under the hood detailing, you may only need to go through the degrease-scrub-and-rinse process once. But in the off-chance that the engine’s a little too grimed up, don’t be afraid to run through the process again.

Repeat steps 5 (degrease), 6 (scrub), and 7 (rinse) a couple more times until you’re certain all the dirt and oil have been removed.

Step 8: Dry Engine Bay Immediately with Microfiber Towels

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Leaving the engine compartment to air-dry is a viable option–especially if you’re working in a closed area with good ventilation and manageable temperature.

But air-drying depends on elements we can’t control, so it’s impossible to estimate how long you’d have to wait. Plus, you risk letting the water run and drip onto the sensitive parts in the compartment while waiting.

So it’s best to just take charge of the drying process yourself.

Use a leaf blower or air compressor to dry the engine bay–especially in areas where water can accumulate.

You can even run a dry rag, microfiber towel, or chamois over the whole compartment once you’re done to make sure there aren’t any damp spots left.

Step 9: Remove Plastic Bags and Restore Parts Under Hood

Once everything’s nice and dry, remove the plastic bags covering the sensitive parts and re-install the parts you took out earlier (i.e., filters and battery cables). Just to be on the safe side, go ahead and wipe the plastic bags with a dry cloth before removing them.

As for restoring the filters and cables, exercise the same care and caution you took when taking them out. Again, this will require some skill and knowledge. If you had someone else take the parts out, have them handle the re-installation process, too.

Close the hood when you’re done and, voila–you’ve successfully cleaned under your car’s hood.

Common Mistakes to Avoid When Clean Under the Hood of a Car

how-to-clean-under-the-hood

  • When you detail under the hood, it’s necessary to (1) pay attention to the temperature of the engine. One of the biggest mistakes people make when cleaning the engine bay is spraying a hot engine with a high-pressure stream of water.

You risk short-circuiting a cable, shattering parts of the engine, or accidentally disconnecting a sensor.

  • Another common cleaning mistake people make is (2) air-drying the engine bay using a high pressure setting.

If you’re using an air compressor or leaf blower to dry your engine, strong, persistent gusts of air can push water deeper into cracks and hard-to-reach crevices, forming little pools that can’t easily be detected. Light, consistent pressure is more than enough to dry the area.

  • Finally, the last common mistake people make when cleaning under the hood of a car is (3) they don’t do it often enough. Experts agree that the best way to keep an engine bay clean is to detail it at least twice a year.

Even if you can’t do it yourself (no time, no tools, no practice, etc.), you can still approach any under the hood cleaning service. Professional auto detailers are more than capable of polishing your engine to perfection every time!

Is It Safe to Wash Under the Hood of Your Car?

Generally speaking, yes, you can spray water under the hood of a car. However, you need to consider several factors:

  • The engine needs to be at a cool enough temperature to avoid shattering. S
  • ensitive parts in the compartment should be covered with plastic (fuse box, air intake, sensors, relays, etc.) or taken out completely (air filters and battery cable) to minimize risks.
  • There should also be tools to immediately dry the area under the hood on hand–like a leaf blower or dry microfiber towels.

Once all these are taken into consideration, you should be able to pressure wash under your car’s hood with no problem.

Conclusion

A clean engine – free of dust, dirt, and caked-on grime – will always look, sound, and perform better than one whose last detailing session was several years ago.

And hopefully, now that you know how to clean under the hood of a car, you won’t shy away from the process.

Yes, some steps can require much effort. But, in general, proper vehicle maintenance includes maintaining what’s under the hood of your car. This boosts its longevity and reliability by a considerable percentage.

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Our chief editor is Sam Howard. The vast market of car care necessitates extensive research. He entered the market, experienced the service, and reported customer feedback in order to provide the best advice and content to car owners. We have faith in him to turn our website into a reliable resource for all car owners.