How to Determine if Water Has Entered the Engine After a BMW Stalls in Water
2 Answers
Oil is a mineral oil, and theoretically, it can be of any color. Common oils are transparent, colorless, light yellow, brown, etc., but they will not be milky white. After pulling out the oil dipstick, wipe it and reinsert it. If the color appears white when taken out again, it may indicate the presence of water. At this point, the oil filter needs to be replaced. If obvious water marks are found in the air filter, it is possible that water has entered the engine. When the engine is working normally, each cylinder reaches the same top dead center position. If water enters the engine, since water cannot be compressed, it will cause the top dead center position to fail to reach its original position and move downward.
As a former professional automotive technician, I've handled multiple cases of BMW vehicles stalling after water exposure. If water enters the engine after wading, the risks are extremely high, especially given BMW engines' high precision. First step: Never restart the engine! Park and inspect immediately: Pull out the dipstick to check if the oil appears emulsified or shows water droplet marks; if the oil turns white or foamy, it indicates possible water intrusion. Second, remove the spark plugs for inspection: If the extracted spark plugs are soaking wet, that's definitive proof of water entry. BMW's air filter box sits relatively low, making it more prone to water intake; open the box cover to check if the filter is soaked. Finally, for safety, immediately call a tow truck to take the vehicle to a repair shop for thorough cylinder inspection using a borescope. Water compression inside the engine can cause piston deformation, potentially resulting in repair costs exceeding tens of thousands. Remember: When wading, never exceed half the wheel height as prevention is always wiser. Don't move the vehicle before professional assessment - this could save you from major repair expenses.
