Can Water Enter the Engine Through the Spark Plug?

[VonAlexandra]

Under normal rainy conditions, water will not enter the spark plug of a car unless the rainfall is extremely heavy, reaching the level of the car's hood. In such cases, water can seep into the spark plug from under the hood. Spark plugs are installed on the side or top of the engine. In earlier models, spark plugs were connected to the distributor via ignition cables. However, over the past decade, most car engines have switched to direct connections between the ignition coil and the spark plug. Under high voltage, the air between the center electrode and the side electrode of the spark plug rapidly ionizes, forming positively charged ions and negatively charged free electrons. When the voltage between the electrodes reaches a certain level, the number of ions and electrons in the gas increases like an avalanche, causing the air to lose its insulating properties. A discharge channel forms in the gap, leading to a "breakdown" phenomenon. At this point, the gas becomes a luminous body, creating a "spark." Along with the heat expansion, a "crackling" sound is also produced. The temperature of this electrical spark can reach 2000–3000°C, which is sufficient to ignite the air-fuel mixture in the engine's combustion chamber.

[Faith]

I remember one time after it rained, I drove home and forgot to cover the engine hood when parking. Rainwater dripped onto the spark plugs. Later, when I tried to start the car, the engine wouldn't fire. The mechanic checked and said water had seeped into the combustion chamber through the spark plug holes due to aging spark plug seals. Water can indeed enter the engine interior, especially if the seals are not tight. During engine startup, piston compression can draw in water, potentially causing hydro-lock and damaging the piston or connecting rod in severe cases. This taught me a lesson: now I regularly check spark plug seals, avoid direct high-pressure water spray on the engine area during car washes, and recommend replacing spark plugs every two years or as per the manual to prevent accidental water ingress.

[OElaina]

From a professional perspective, water entering the spark plug may directly reach the engine combustion chamber. Spark plugs are installed on the cylinder head, with holes leading directly into the combustion chamber. Water infiltration can dilute the air-fuel mixture, causing starting difficulties, misfires, or knocking. Prolonged water exposure may also corrode piston rings or cylinder walls, affecting sealing and performance. During maintenance, focus on checking the spark plug installation torque and seal integrity; if water ingress occurs, do not start the engine—drain the water immediately and replace damaged components. Daily precautions such as avoiding deep water crossings and checking engine compartment dryness after rain can effectively reduce risks.

[EmmaLee]

As a car owner, I once accidentally splashed water onto the spark plugs at a car wash. Later, the mechanic told me that water can easily leak into the engine around the spark plugs. If the engine isn't running, it's not a big deal, but once started, the water can be sucked into the combustion chamber, potentially causing shaking or stalling. It's recommended to regularly check if the spark plugs are properly covered after parking, avoiding exposure to rain or high-pressure washing. If water gets in, don't start the engine—seek professional cleaning for safety.