How to Clean an Engine The Right Way

Aside from bragging rights when you pop the hood, a clean engine will helpfully betray problems like leaks, making them easier to track down.

under the hood clean engine
Gear Patrol Studios
Editor's Note: In this limited series, Under the Hood, we'll share do-it-yourself tips for drivers who want to wrench their own cars, no matter their skill level.

Despite being protected by the hood and body panels, your engine routinely picks up debris from the outside world: leaves, twigs, dust, grime and other… stuff will always find their way inside. Cleaning your engine isn’t only about aesthetics; a clean engine will ultimately run and perform better and last longer without maintenance since all its components are contaminate-free.

Don't Clean a Hot Engine

To clean your engine compartment properly, after shutting off the car, wait at least 15 minutes for it to cool completely. To be absolutely safe, there's no harm in waiting half an hour or longer. Somewhat counterintuitively, it will be easier to clean your engine if the weather is warm since it will dry more readily after a good rinse.

Cover Up

When your engine has reached a workable temperature, first prep and protect every component that shouldn't get wet. Use cut-up plastic bags, plastic wrap or similar materials to cover any exposed wiring; remove any decorative plastic parts like engine covers; and either cover or carefully remove the battery. Cover electrical parts like the distributor, ignition wires, engine control unit (ECU) and basically anything else you wouldn't feel confident bringing into a bathtub with you.


(Purchase any supplies and tools mentioned below from eBay Motors or your retailer of choice.)

clean car engine

It’s important to use non-corrosive cleaning substances. Experts agree that most household degreasers, like Simple Green or Easy Off, are appropriate for engine clean-up, though myriad products are marketed specifically for cleaning engines. Whatever you use, first spray the entire engine bay, leaving no stone unturned–aside from everything you covered in the previous step, of course. Allow the degreaser to sit for about five minutes to really dig into the worst of any crud.

Rub and Rinse

clean car engine

Depending on how dirty your engine is, you may have to add little grease of the "elbow" variety. If so, use brushes with synthetic bristles (plastic, not metal) or sturdy shop towels to scrub problem areas. You may have to apply another round of degreaser and repeat the scrubbing step depending on how gnarly your situation is.

When you're confident that the gunk is gone, it’s time to rinse. Use a garden hose or a power washer (on its lowest setting) to slowly work your way from the rear of the bay to the front. Take care around anything you covered up, ideally avoiding them altogether, and focus on areas that took the most work to clean.

Time to Dry

If you have an air compressor, you can use it (again, on a low setting or by metering the air carefully) to remove any standing water on the engine or in the compartment. Again, be careful around those delicate covered areas. If you don’t have an air compressor, a leaf blower can work in a pinch, but it's probably less of a hassle to wipe down surfaces and sop up water and grime with shop towels.

clean car engine

After getting most of the moisture, leave your hood up for a while to let the engine dry off completely. Then, carefully remove any and all coverings you’ve placed on electrical components–you don't want a garbage bag getting caught in your fan belt or melting to the engine (which will happen VERY fast if you leave one in there and start the car). Reinstall any plastic covers you removed and replace/reconnect the battery.

That's it: a simple but somewhat tedious process that should take just a few hours to complete and one that should be done every year or so or after buying a used vehicle. Aside from bragging rights when you pop the hood, a clean engine will give away any leaks, drips or physical issues much more plainly than one with caked-on mud, oil and other… stuff.

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