Is There Any Impact If the Engine Is Washed with a Water Gun?

[AdrianaFitz]

It is not recommended to use water to wash the engine compartment, as it may cause certain damages and safety hazards. Here are the relevant details: You can use cleaning agents: If there is oil sludge on the engine's exterior, you can use cleaning agents for washing, then dry it with an air gun or a cloth. Do not use water to wash the engine, as the engine contains many electrical components and cable connectors. Each of these connectors has a sealing ring that provides simple waterproofing. Using a car water gun for washing risks breaking the sealing rings of the connectors, leading to water ingress. Precautions: Additionally, if there is oil sludge on the engine casing, it is not easy to clean it thoroughly with water. Lastly, it is important to note that when cleaning the engine, always wait until the engine temperature returns to normal. Cleaning the engine while it is still hot can easily cause damage to engine components or reduce their lifespan.

[ManuelDella]

Last time I went to wash my car, I did exactly that, and the next day the engine malfunction light came on. The mechanic said nowadays the engine bay is full of delicate electronic components, and that square engine control unit is most afraid of water. If water gets into the sensor connectors, they can rust. High-pressure water jets can force mud and debris into wiring harness connectors. The most dangerous spot is the air filter box area - water pouring in there can flow directly into the cylinders! For proper cleaning, you should use low-pressure mist when the engine is cold, scrubbing with a brush while washing, and finally use an air gun to dry all connectors and interfaces. Now I always disconnect the negative battery terminal before cleaning to be safe.

[MatteoFitz]

Once I enthusiastically sprayed the engine at a self-service car wash, and on the way home, I felt the acceleration was sluggish. When it was taken apart at the repair shop, it was found that the spark plug sockets were filled with water, and the coils were soaked white. The mechanic said these high-voltage coils could short-circuit if they got wet, and the fuel injector connectors would rust if submerged for too long. The most troublesome part was the wiring harness clips near the power steering pump—once water got in, it couldn’t get out. Now, I have them use special foam spray and a fine brush for cleaning, wiping the throttle body with a damp cloth. The car factory’s pipe design has waterproofing, but it really can’t withstand a direct high-pressure water jet.

[GenevieveMarie]

Don't ever imitate those TikTok videos of spraying water guns at the engine! After our family car got sprayed, moisture got into the fuse box, causing the power windows to malfunction. The oxidized and broken copper wires in the wiring harness cost over 800 yuan to repair. Now we only use dedicated engine bay cleaning foam for washing. Spray it on, wait five minutes for the grease to dissolve, then slowly wipe it off with a damp towel. Remember to especially avoid the fuse box, alternator, and ignition coils. There's usually a drainage hole at the bottom right of the engine bay—it's more practical to clear it with a wire occasionally.

[MargaretDella]

Last summer, I used a garden hose to wash the engine, and water seeped into the cabin through the hood gaps, soaking the foot mat under the passenger seat. The dealership said the engine wiring harness assembly needed a full replacement due to water damage, quoting over 5,000 RMB. They taught me the correct method: wait for the engine to cool, then use a spray bottle to moisten specific areas, and for stubborn grease, apply WD40 on an old toothbrush to scrub. Key points are to cover the alternator and air intake, avoid starting the engine immediately after washing, leave the hood open to dry for two hours, and ideally use compressed air to blow dry the wiring harness connectors at the rear of the engine.

[LouisLee]

I've seen too many tragedies of engine washing in modification shops. The most extreme case was when a high-pressure water jet displaced the crankshaft position sensor, causing the engine to immediately throw a fault code. Water pressure exceeding 8 kg can flush out the waterproof plugs of wiring harnesses. Nowadays, the engine control units of BMW and Mercedes are all located in the engine bay, and repairs can cost upwards of 20,000. If you really want to clean it, buy bottled engine bay cleaner and use it with a detailing brush and a tornado gun (note: it's pneumatic, not water). After washing, remember to dry the ECU connectors with a heat gun—don't make do with a hairdryer.