How to Determine if the Engine Has Taken in Water When the Car Can Start
2 Answers
After a car has been submerged in water, it's necessary to determine whether the engine has taken in water. Here are the detailed steps: 1. Check the water submersion height: If the water level reached above half of the wheel, there is a possibility of engine water intake. 2. Inspect the air filter and intake pipe: Look for obvious signs of water ingress on the air filter and check if there are water traces in the intake pipe and intake manifold. 3. Examine the engine oil: Pull out the dipstick. Oil without water appears as a translucent, shiny liquid, while oil containing water will appear opaque with a brown or yellowish color. If the oil contains water, after the engine runs for a while, the oil will turn milky white and may have foam. 4. Check the spark plugs: Remove the spark plugs from each cylinder and inspect if they are wet. Wet spark plugs indicate signs of water in the engine. 5. Use diagnostic tools to check carbon deposits on the engine cylinder walls: Under normal conditions, all pistons reach the same top dead center position, and the cylinder walls show clear markings. When water enters the engine, since water is difficult to compress, the piston stroke shortens, causing the top dead center position to noticeably lower.
I remember once driving a car through water, and it still started afterward, but I always suspected the engine had taken in water. The key method is to check the oil: open the engine oil cap or pull out the dipstick—if the oil appears milky or foamy, that's a sign of water contamination. Also, inspect the air filter box—gently remove the filter element, and if you find it damp or with water marks, it means water has entered the air system. After starting the engine, observe the exhaust pipe; white smoke indicates water evaporating in the combustion chamber. Additionally, listen for unusual engine sounds, such as wheezing or knocking. Minor water ingress might not immediately affect startup, but don’t take it lightly—shut off the engine right away and have it towed to a professional repair shop for inspection. Otherwise, it could lead to internal rust or severe damage, affecting pistons or cylinders. Remember, safety first—don’t force the car to drive to avoid worsening the problem. I’ve personally experienced this, and timely action saved the engine from total failure.
