Skip to main content
Skip to page content

Cleaning an engine

The engines of most modern cars or trucks generally don’t need much polishing, yet even minor debris in the wrong place can do damage. That doesn't mean that you need to build a home garage and get down and dirty working on the engine. It just means that you want to keep an eye on the engine – just as you do the gas gauge and warning lights on your dash.

How to clean your car engine

Why it’s important to clean your engine bay

"It’s always a good idea to open the hood of your vehicle to see what’s going on there," said Richard Reina, product training director at CARiD.com and veteran auto expert. "While it’s unlikely for a leaf or twig to enter the engine, a more likely scenario is that [debris] can block a drain or get stuck in the wiper mechanism. If it doesn’t belong there, remove it." Modern automobiles are built with the radiator positioned in such a way as to protect more delicate parts of the engine, but you should still take a look under the hood once in a while. A monthly check is ideal, but even twice a year can head off problems, auto experts say. That’s especially true for those who drive in dusty, sandy or unpaved roads or drive more than 25,000 miles a year.

"Most motorists are not going to have engines that are very dirty, but they may find coolant or oil leaks," said longtime industry expert Ed Kriston of Westminster, Maryland, and former territory manager of AAA Mid-Atlantic, noting that leaked fluid can attract dirt, dust and other contaminants that may damage the engine. "It’s good to catch those early."

But just how do you clean the engine if it has become greasy or attracted foreign matter? Consider this advice:

Ensure the engine is cold – Not only can you injure yourself if you work on a hot engine, but cleaners and water can cause severe damage. Make sure the engine is cold before you begin.

Choose your cleaner – Remove any stray branches, leaves and debris. You can buy a cleaner designed to degrease the engine compartment. However, Reina recommends checking your home cleaning supplies first. Simple Green® cleaner and a small amount of Dawn® dishwashing detergent work well to degrease. If you’re unsure what to use, it’s best to go to an auto store and choose an "engine cleaner/degreaser," said Reina. Reina also saves old toothbrushes to clean smaller areas. Kriston recommends using a clean cotton rag to remove the grease. Don’t use a heavy bristle or wire brush, because those can bend critical engine components.

Rinse with extreme care – "You always see people spraying their engines and then having electrical problems," said Kriston. "When you start rinsing the engine off with the hose, you have the possibility of getting water into connectors and electrical parts of the car. Then all of a sudden, the engine won’t start." The bottom line: Never spray water if it can get into the engine. And make sure the engine is cold if you do spray it or you can "cause the engine block to crack from the temperature differential," Reina said. If you do need to rinse the engine, he recommends taping plastic bags over electrical items.

Avoid pressure washers – Even at a low setting, pressure washers can wreak havoc. Reina recommends that only those very familiar with such tools and their engines attempt to use them.

Dry thoroughly – After rinsing the engine, towel-dry it. Remove as much water as possible. Then start the engine. The heat will dry residual water, Reina said.

Take proactive measures – Tires kick dirt, sand and salt into the underside of the car. Opt for underside spraying at a commercial car wash. If you wash your car at home, Reina recommends using a high-pressure garden hose to spray all four wheel wells. Reina jacks up one side of the car, sprays the wells and then repeats on the other side.

Remember the battery – Although battery maintenance is not part of engine cleaning, it’s important to clean it regularly. "At a minimum, both battery terminals should be disconnected, with battery posts and cable ends cleaned with a wire brush," said Reina, who explained that the top of the battery should also be wiped clean. "A good solution to use is a mixture of baking soda and water."


Nancy Dunham is based in Washington, D.C., and writes for Automotive News, National Automobile Dealers Association and other major publishers.

Energy lives here