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How to Wash an Engine Properly

Knowing how to wash an engine will leave you with a sparkling engine bay.

vehicle engine

You probably wash your car regularly. Some people wash and wax weekly — even do interior detailing — but many forget the engine. After all, it’s out of sight and out of mind. Before picking up a pressure washer and just blasting away at the engine bay, however, you need to know how to wash an engine the right way without destroying anything in the process.

Can you destroy anything this way? You absolutely can. The truth is, while there are many durable items under the hood, there are plenty of things that you could ruin by not using the proper tools, particularly electrical components and electronic sensors and controls. Here’s a look at how to wash an engine without damaging those things and get the job done right.

Engine Cleaning Steps

  1. Some covers can be removed by hand or by removing a couple of bolts, so you can clean under them, too. Use your fingers and a hand brush to remove dried leaves and other debris. The air gun works great for blowing this stuff away.
  2. Run the engine for a few minutes until it’s warm to the touch, but not to full operating temperature. This will help the degreaser work better.
  3. Cover the distributor, alternator, and fuse and relay boxes with plastic bags to prevent too much water from causing short circuits. True, they get wet on rainy days, but nothing like what comes next.
  4. Coat everything with a foaming engine degreaser. You can try to get at the engine from under the vehicle, as well, and ramps or jack stands will improve access. Let the degreaser soak for a few minutes and reapply it in dirtier spots.
  5. From the top down, use the garden hose or pressure washer to rinse the engine. Use the 40- or 25-degree pressure washer nozzle for cleaning and rinsing, but never the 15- or 0-degree nozzles. The latter won’t affect metal, but could strip the paint off parts or cut through plastic and rubber parts, wires, tubes or hoses.
  6. Remove the plastic bags, and use degreaser on a rag to surface clean the parts underneath. Use a damp rag to wipe degreaser residue from the surface.
  7. After thoroughly rinsing, use rags or compressed air to dry the engine. Remove fuse and relay box covers and use compressed air to blow water out of them.

Benefits of a Clean Engine

Keeping your engine clean comes with several benefits:

  • Lower engine temperatures: A clean engine runs cooler, improving engine performance and fuel economy.
  • Easier to work on: A clean engine is easier to work on. Diagnosing leaks is simpler and repairing a clean engine won’t leave you looking like a grease monkey.
  • Higher resale value: A clean engine also improves resale value if you sell it. A dirty engine bay says you don’t care for your car — a prospective buyer will assume the worst.

The next time you think of washing your car, pop the hood and see if the engine bay deserves a little of your attention.

Check out all the chemical products available on NAPA Online or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on how to wash an engine, chat with a knowledgeable expert at your local NAPA AUTO PARTS store.

Photo courtesy of Wikimedia Commons.

Benjamin Jerew View All

Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.

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