What Happens When an Engine Is Submerged in Water?

[DanteRose]

Effects of a submerged engine: The engine connecting rod deforms, leading to shortened piston stroke and insufficient gas compression. The piston rings lose elasticity or fail to seal, causing gas leakage. Compressed gas leaks into the crankcase. The intake and exhaust valves do not seal properly when closed, resulting in compressed gas leaking into the intake and exhaust manifolds. Below is an introduction to flood-damaged vehicles: 1. Definition of flood-damaged vehicles: Flood-damaged vehicles refer to cars that have been submerged in water, typically involving the engine and transmission being soaked, with water depth exceeding the wheels and body seats. These are vehicles where the underbody components have been in prolonged contact with water. Such vehicles pose significant risks, as the electrical systems are prone to short circuits and fires. 2. Hazards of flood-damaged vehicles: (1) Components are prone to damage. (2) The engine may suddenly stall. (3) Airbags may fail to deploy in critical moments or deploy unexpectedly. (4) They are highly likely to cause rusting of body components, reducing service life and compromising safety performance.

[JaceFitz]

I've encountered many cases where cars got flooded during heavy rains, and once the engine takes in water, the problems can be severe. Water can enter the cylinders, and if you attempt to start the vehicle under such conditions, the connecting rods may bend or even break, leading to a major overhaul. If water seeps into the oil pan through the intake pipe, the engine oil will emulsify and deteriorate, losing its lubrication function entirely. The most dangerous part is the electronic components—for instance, the ECU circuit board could short-circuit or catch fire if submerged. Therefore, if you discover your car has been flooded, never attempt to start it. Call a tow truck immediately to take it to a repair shop. A thorough inspection is necessary, including changing the oil, cleaning the cylinder block, and drying out the wiring. In the worst-case scenario, you might need to replace the entire engine, which can be extremely costly.

[LeviAnn]

Last year, my friend's car got submerged in a heavy rainstorm, and the engine was completely destroyed. The mechanic said that when water enters the cylinders, it obstructs piston movement, and forcing a start can bend the connecting rods, making repairs both complicated and expensive. Additionally, spark plugs short-circuit when wet, and the electronic systems are prone to failure. Even if repaired, various issues may arise later, such as engine knocking or sudden increases in fuel consumption, because water can corrode internal components. Now, I always avoid parking in low-lying areas. If caught in a flood, I turn off the engine, cut the power, open the windows to escape—safety comes first.

[GabrielRose]

The worst thing after engine flooding is the owner forcing ignition. I've seen too many people panic and turn the key, only to double their losses. Water in the cylinders is like pouring in concrete—the crankshaft can't rotate and ends up bending the connecting rods. Spark plugs and oxygen sensors are ruined upon contact with water, and repairs can cost thousands just for parts. The bigger issue is the hidden dangers afterward: flooded fuel lines and electrical circuits are prone to oxidation and short circuits, potentially causing sudden failures months later. So if flooding occurs, stop immediately and wait for professionals to disassemble and clean everything, from the air filter to the oil pan, for a thorough inspection.