Our Mechanic Next Door runs down the top six reasons–and foolproof steps–for cleaning your vehicle’s engine.
If you’ve ever purchased a new or used vehicle from a dealer or prepped for a car show, you know just how clean an engine compartment can look. The metal gleams, the black hoses glisten, and you can touch any surface and not come away covered in dirt, grease or oil. Conversely, every driver knows that it doesn’t stay that way long as things get nasty under there in a hurry – a fact we’re reminded of every time the hood’s popped to check fluids, do some work, or investigate a disturbing new noise, vibration, or smell.
Drivers clean their vehicles’ interiors and exteriors, but by and large tend to ignore the engine compartment, allowing grit and grime to accumulate over the years and miles. Whether you don’t clean under there because you don’t know how and are afraid you’ll damage something, or you’re a seasoned do-it-yourselfer but just don’t think it’s important, consider these thoughts and tips on engine cleaning.
Why do it?
Sure, a clean engine looks great, but that’s just one of the reasons for tackling this project. Here are some reasons you may not have thought of for cleaning your engine and engine compartment:
- It’s easier to spot potential trouble before it becomes a major problem. If your engine is filthy, you’re not going to know if that small fluid leak has been there forever, or if it just appeared. Clean engines make leaks, cracks and other problems easier to spot.
- Remove road salt and debris that can lead to corrosion if they’re allowed to accumulate.
- Remove debris that can cause hot spots to form on the engine and its components, shortening their lives.
- Prevent the buildup of combustible materials, such as leaves or oil, that are fire hazards on the road and in the garage.
- A clean engine is more enjoyable to work on and look at.
- A vehicle with a clean engine and engine compartment has a higher resale value.
Make it shine.
Ask ten different DIYers how to clean an engine and you’ll get 10 different answers. It’s not rocket science, but it’s also not something you should dive into without possessing some knowledge. Back in the day, the preferred method of cleaning an engine was to steam clean it. Cheap, easy, and it got the job done. Times change, as do engines, and steam cleaning isn’t the best option any longer because of the sensitive electronics in the engine compartment. Fortunately, there’s an alternative today – engine cleaners.
First, browse the various engine cleaning and degreasing products available. There’s water-based, solvent-based, gel, foam, spray bottles, aerosol cans – you name it. I prefer a solvent-based cleaner because it cuts through grease and grime better than a water-based one, which translates to less effort and elbow grease for me trying to scrub away stubborn dirt. I also migrate toward gel-based engine cleaners because I like the way they stick better to vertical surfaces, giving the cleaner’s scrubbing action more time to work on the surface, and me more time to do something else.
How engine cleaners work is a mystery to me, mainly because I’m not a chemist. The Material Safety Data Sheet (MSDS) for Gunk Foamy Engine Brite Cleaner includes propane, 2-butoxyethanol, aromatic petroluem naptha, isobutene, and petroleum base oil as ingredients. I don’t know what they do, except work well, but I imagine the solvents and other ingredients break down the grease and grime and reduce its surface tension, making it easier to wash away.
In addition to choosing a cleaner/degreaser, you’ll also want to pick up a drip pan and some absorbent pads. Why? A lot of oil and other chemicals will be rolling off your engine when you clean it and this hazardous cocktail shouldn’t be going onto your driveway, into a storm water drain, or seeping throughout the ground. Instead, capture the dirty fluids on the pads and drip pan, allow the pads to sit in the sun until the water evaporates, and then find a local recycling center that accepts both the used pads and the oily water from the drip tray.
Once you have all your supplies, use an air compressor or can of compressed air to first blow away any loose debris that may have accumulated under the hood.
Next, start the vehicle and let the engine warm up – but just a little. You want it warm to help break up the grease when the cleaner is applied, but not so hot that you can’t touch it and that it presents a fire danger when sprayed with a solvent or when oil and grease start moving around. Also, a hot engine sprayed with cold water is a sure-fire way to damage an engine and other vehicle parts.
Once it’s warmed up and the engine is off, wrap all visible electronic connections and components in plastic wrap or plastic bags to prevent water from damaging them. Cover the alternator and all filters and the air intake as well.
Position the drip pan and absorbent pads under the engine, then apply the engine cleaner – following the manufacturer’s instructions – and wait for the magic to happen. While the cleaner is working, look for any areas that have a lot of grease or dirt and scrub those spots with a plastic-bristle brush or rag.
Once the cleaner has been on there for the recommended period of time, rinse it and the dirt off gently. Engine cleaning is not a job where you want to use a car wash hose or home pressure cleaner because the water pressure is too high and could force moisture into sensitive engine parts. Instead, use a gentle spray from a garden hose, being sure to avoid electronic components as much as possible. Once the rinse is complete, the compressed air will come in handy again to blow any water out of crevices where it may have accumulated.
When you’re satisfied with the appearance, remove the plastic coverings applied earlier, start the engine and let it reach operating temperature to help evaporate any remaining water.
When the engine has cooled, apply a rubber or vinyl protectant to hoses and plastic components. Then, step back and admire your very clean, very shiny, and very satisfying engine bay, and ask yourself why you waited so long to clean your engine.
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*Always consult your owner’s manual first. Follow the manufacturer’s recommendations to ensure warranties are not voided.