2016~2021 Cleaning and dressing the engine bay

sm1ke

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'18 CX-9 Signature
This is a DIY How-To that explains how I cleaned and dressed the engine bay of my 2018 Mazda CX-9. The guide should be applicable to all 2nd generation CX-9s. Hopefully this becomes a useful reference for anyone curious about this process.

This process was documented/photographed by myself, using my cellphone camera and my 2018 Mazda CX-9 Signature as the "demo" vehicle. This DIY is provided as a learning aid and reference guide. I assume no responsibility for any damages you may inflict on yourself or your vehicle.

What I used:

- A brush (I used a wheel brush to get into tight areas, but a baby bottle brush would be just as good)
- Aluminum foil and plastic bags
- Super Clean (some other kind of engine degreaser would work as well)
- A garden hose to rinse with
- Microfiber or terry cloth, or a leafblower
- 303 Aerospace Protectant


First thing's first - don't do this on a hot engine! It's really easy to accidentally burn yourself if you aren't familiar with what you're touching. Secondly, if you want to be as safe as possible, you can disconnect the negative terminal cable from the battery and move it out of the way.

1. You don't have to do this, but you can drive the car around the block if its been sitting for a while to get the engine bay warm, but not hot. This will soften up the existing dirt and grime under the hood and make it a little easier to brush off.

2. Remove the engine cover. You just have to give it a good pull straight up and it will come out. Set it aside.

3. Cover the battery with a plastic bag to avoid getting it wet.

4. Cover the alternator, the top of the engine and any exposed plugs with aluminum foil. I used foil for this part because it's easy to wrap it around certain parts and it will stay in place. These parts don't need to be covered up as tightly as possible, I just did this to prevent the majority of water from getting onto/into those parts. Pretty much everything under the engine bay is water resistant. NOTE: If you have an exposed engine air filter (like the CorkSport, K&N, AEM air filters), cover the air filter element.

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5. Spray the underside of the hood with Super Clean, then use the brush to agitate all surfaces. Rinse with a steady stream of water from the garden hose. NOTE: Avoid getting Super Clean on the exterior painted surfaces, as it can cause damage to the clear coat. Under the hood is fine because none of those surfaces are clear coated.

5. Spray the engine bay liberally with Super Clean, then use the wheel brush to agitate all surfaces. Be careful around plugs, sockets and wires, as you don't want to accidentally unplug a socket or damage a wire because you were brushing too hard. Rinse well with water.

6. Dry the underside of the hood and the engine bay with a microfiber cloth or a leaf blower.

7. Remove the aluminum foil and carefully remove the plastic bag from the battery.

8. Using a damp rag, carefully wipe down the battery, top of the engine, and any other spots you might have missed with the brush. Below is a photo of the engine bay with the engine cover off, and all areas wiped clean and dry. If you disconnected the negative battery terminal, you can reconnect it now.

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9. Spray the engine cover with Super Clean and brush it down, then rinse with water. Reinstall the engine cover by lining up the pins with the sockets. Below is a shot of the engine cover reinstalled.

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10. To dress the engine bay, spray a coat of 303 Aerospace Protectant on the entire engine bay (avoid the battery terminals). You want an even layer to ensure that it doesn't appear splotchy when it dries.

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11. Let the 303 sit for a couple of hours. Wipe up any excess 303 that may have pooled up, and you're done!

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NOTE: If you don't want the glossy look, instead of spraying the engine bay with 303, you can just spray some 303 into a clean, damp microfiber towel and do a hand wipe of all the parts you want to dress. It should leave a nice satin finish.


Hope that helped you guys out! If you have any questions, post them here and I'll do my best to answer them.

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