Why Should You Not Restart a Vehicle After Water Wading?

[OValentina]

Here are the reasons why a vehicle should not be restarted after water wading: 1. Specific reason: If water is sucked into the cylinders during engine water wading, it can cause the engine to stall. Forcing a restart at this point will cause the starter to turn the engine, forcing the pistons to compress the water. Since water is incompressible, the result is damage to the engine's crankshaft and connecting rods, requiring major engine disassembly for repairs. 2. Precautions: Increase the safe following distance because wet roads are slippery, visibility is reduced, and emergency braking can cause skidding. Drive at a steady, slow speed and avoid unnecessary lane changes. Rainwater accumulation on side mirrors and windows can obstruct the driver's view of the surroundings. Most accidents during rainy days involve minor collisions due to poor visibility when changing lanes.

[Zane]

Yesterday I saw a video where a guy drove through a puddle after rain, stalled, and then tried to restart the engine, which ended up completely destroyed. The principle is actually quite simple: when your car stalls due to water exposure, water can backflow from the exhaust pipe into the cylinders. But when the piston operates, the cylinder is a sealed space, and water is virtually incompressible. If you forcibly attempt a second ignition, the piston slams upward like a fist hitting an iron plate, resulting in bent connecting rods, shattered pistons, and even punctured cylinder walls. What's worse is that insurance will deny claims for damages caused by restarting the engine after water exposure. If you ever find yourself in a situation where the front wheels are half-submerged, the smartest move is to shift to neutral and call a tow truck.

[Gordon]

With twenty years of auto repair experience, I've seen countless cases like this. After stalling in water, the engine is still breathing, allowing water to seep into the cylinders through the intake. Unlike air, water can't be compressed—when you turn the key, the crankshaft drives the piston upward, and the resistance from the water forces metal to clash. Aluminum pistons smashing into steel valves can bend valve stems or even twist connecting rods like pretzels. The worst part? You'll foot the repair bill—insurance policies explicitly state 'damage from restarting after water ingress isn't covered.' My advice: maintain steady throttle through water, and if RPMs suddenly drop, shut off the AC and shift to neutral immediately.

[RiverMarie]

Let's do the math: A major engine overhaul for a regular family car starts at least at 20,000 RMB, and replacing the cylinder block assembly can easily exceed 35,000 RMB, none of which is covered by insurance. The critical point is that water backflow takes only ten seconds, with the air intake just about 40 cm off the ground—water half a wheel deep is enough to flood it. The moment you restart, the air-fuel mixture contaminated with water in the cylinder ignites, causing a sudden pressure surge that cracks the piston rings, and the fragments will score the cylinder walls. The most extreme case I've seen was an owner who forced a start three times, ending up with a repair bill high enough to buy a used Jetta.