I have a cluttered bedroom. To me, it’s a place where I lay down to check if there’s a new episode of Roadkill on my laptop and not much else. But my cars – they have to be damn near spotless. To help with that, here’s how to clean one of the most forgotten places on a car’s body without screwing it up. Honestly, we often forget a critical piece of maintaining our cars, and that is polishing using of course the best car polish.

Contrary to popular belief or whatever your crazy uncle says, engines don’t need dirt or oil on them to work properly. In fact, when an engine is clean aesthetically, it can cool more efficiently, there’s less wear on things like bearings and pulleys, you can single out leaks, and there’s less chance of you sucking in dirty particulates into your filter.

For today’s demonstration, I’m using my new-to-me 1995 Honda Accord EX with 171,000 miles of dirt and debris concentrated in its engine bay. Here’s the car as I got it, in all of its oil-soaked glory:

While not the worst that I’ve seen, the engine bay could use bit of tidying up, especially since the levels of various fluids aren’t able to be measured due to the dirt buildup around the markings. That’s kind of important.

The first thing to do is to make sure you do this on a warm day where water can adequately evaporate. You’ll be introducing water into places where it might not have been designed to go, so the ability to dry off is essential.

Remove the negative battery terminal.

Then grab a garden hose with a nozzle attachment, or if you’re fancy like me, a cheap pressure washer.

You’ll want to mask off all the sensitive electrical components – the main ones on this car being the alternator and distributor – with plastic bags and tape. Yes, these parts do get wet from time to time from rain, especially if your undercarriage was taken off in an impromptu fight with a curb, but it’s best not to spray them directly with water because water conducts electricity, and I assume you’d like your car to actually run afterwards.

Now you’ll want to take a degreaser like Simple Green or Purple Power, diluted with three parts water, and spray the engine bay down like you’re setting a world record for spray bottle trigger squeezing.

You can use a soft nylon brush to agitate the more stuck on areas, like around the valve cover and you can use an aluminum brush on metal parts like the heat shield and top of the intake manifold plenum. You’ll see dirt already lifting off. Make sure the degreaser doesn’t dry out.

Now you can start power washing or spraying down the engine bay. Work back to front, hitting the firewall first, and keeping your spray moving so you don’t force too much water into the nooks and crannies where it won’t easily come out.

You can now allow the engine to air dry and concentrate on other things, like dealing with the corrosion on the prominent heat shield. I removed the shield, held on by three 12mm bolts, I scrubbed the surface rust off the shield using a steel brush and used a can of high-temp exhaust paint to refurbish its look.

After wiping off any excess water and dirt with a clean cloth and giving all the rubber components a light coat of dressing and reinstalling the negative battery terminal, here’s what I was left with:

I know that the valve cover will need some painting since the years of heat have rendered the existing paint quite brittle, but that’s a project for another day. It’s by no means a show car finish, as many of the metal components can stand to be refurbished, but it looks loads better than the grotty mess that awaited me when I first got it.

The entire process took about an hour and didn’t cost anything other than some degreaser and a little bit of time. It’s possible with any car, and it would be a good bit of preventative maintenance. If you have some dirty-ass engine bays, show them in the comments for them to know more!