Car won't start after flood or water submersion damage

Symptoms

• Car was parked in or driven through significant floodwater
• Waterline visible on the body, seats, or dashboard
• Musty or damp smell inside the cabin
• Electronics may behave erratically if power is applied

Likely causes

• CommonWater in the engine cylinders (hydrolock)Attempting to crank an engine with water in the cylinders can bend rods and destroy the engine.
• CommonWater-damaged wiring harness and control modulesFloodwater, especially if it contained dirt or salt, is highly damaging to modern electronics.
• PossibleContaminated fuel system if water entered the tankWater in the fuel tank prevents proper combustion and can damage fuel system components.
• PossibleCorroded electrical connectors throughout the vehicleCorrosion can develop over days or weeks after a flood exposure.
• PossibleStructural or safety system damage (airbags, brakes)Deep flooding can compromise safety systems in ways that aren't obvious.

What to do

1. Do not attempt to start the engine if the vehicle was submerged past the bottom of the doors or the floorboards were wet inside.
2. Do not connect the battery or attempt to power up electronics until the vehicle has been assessed.
3. Photograph the visible water damage and waterline for insurance purposes before moving the vehicle if possible.
4. Contact your insurance company, since flood damage is often a total-loss situation depending on how high the water reached.
5. Have the vehicle towed to a shop rather than attempting any self-diagnosis of a flood-damaged car.
6. If the water exposure was minor (like light rain or a shallow puddle with no interior flooding), refer to general 'won't start after rain' troubleshooting instead.
7. Do not try to dry out and simply restart a vehicle that was significantly submerged, even if it seems to run, since compromised safety systems may not be obvious right away.
8. Keep all records of the incident and any inspection findings for insurance and future resale disclosure purposes.

When to call a pro

A vehicle with significant flood or submersion damage needs a full professional inspection, and often an insurance total-loss evaluation, before any consideration of repair.

Safety