Can a car engine be directly washed with water?

[Louise]

You can use a water gun to clean it, but the engine must be running during the cleaning process. Avoid pointing the water gun at any single component for an extended period. After cleaning, immediately use a high-pressure air gun to dry the engine to prevent water from entering the wiring harness connectors and causing vehicle malfunctions. Below is a detailed introduction about it: Working Principle: The cylinder injects gasoline and air through the intake and fuel injection ports, mixing them thoroughly inside the cylinder. When the spark plug ignites the mixture, it explodes violently, pushing the piston downward and generating power. Rear Engine: Rear engines are typically found in high-power, rear-wheel-drive vehicles, such as common city buses, highway coaches, and high-end sports cars.

[Barbara]

I've seen too many cases where cars were disabled due to washing the engine with water. The electrical connectors, fuse boxes, alternators, and air intakes in the engine bay are particularly prone to short circuits when wet, especially in older vehicles with aging wiring. Some cars have their ECU located on the side of the engine bay - spraying it directly with a high-pressure washer is practically suicidal. Even if nothing happens immediately, moisture trapped in connectors can slowly corrode metal contacts, causing all warning lights to come on months later. If you really want to clean the engine bay, wait until the engine cools down and use a damp cloth or purchase specialized foam cleaner - it's much safer than using water.

[MariaRose]

Last week, I helped a friend deal with a stalled car, which was caused by him washing the engine with water. Here are the key areas you should avoid washing: Water around the ignition coils can lead to misfiring and engine shaking, while getting the alternator and starter wet can reduce insulation performance. If the fuse box gets wet, it can directly cause a short circuit and burn out the controller. Nowadays, new car engine bays are packed with radars and sensors, making them even more delicate. It's recommended to go to a professional detailing shop for steam cleaning, as high-temperature steam dries quickly and removes oil sludge. If you wash it yourself, disconnect the negative terminal of the battery, let the foam sit for 5 minutes before rinsing with low-pressure water, and make sure to blow dry all connectors afterward—that's the correct approach.

[DePeyton]

As someone who handles cars daily, my advice is straightforward: You can rinse the car with low-pressure water when the engine is cold, but the key is to avoid sensitive areas. When the engine temperature is below 50°C, use a showerhead to wash (avoid high-pressure washers), with special attention to protecting the distributor, fuse box, and air filter intake—these three spots will definitely cause issues if water gets in. After rinsing, immediately use an air gun to dry out areas prone to water accumulation, such as the ignition coil grooves and wiring harness connectors. Remember, many Japanese cars have their ECU computer hidden under the windshield drainage channel, so be extra careful when rinsing. After washing, start the engine and let it idle for 10 minutes to evaporate any remaining moisture for added safety.