Water Damage in a Car: What to Do

What this guide covers

1. If the Car Has Been in Water
2. Not All Water Damage Is a Flood
3. Why the Damage Appears Later
4. What Proper Drying Involves
5. Buying a Used Car: Spotting It

If the Car Has Been in Water

1. Do not start the engine. Not to move it, not to check if it runs, not at all.
2. Disconnect the battery if it is safe to reach, which prevents short circuits through wet connectors.
3. Note how deep the water reached. Above the sills, above the seats, or into the engine bay all mean different things.
4. Get it recovered rather than driven.
5. Open it up to dry, doors, windows and boot, once it is somewhere safe.
6. Lift the carpets. Water sits in the underlay and under seats where nothing dries on its own.

See hydrolock and seized engines.

Not All Water Damage Is a Flood

Most water we find inside cars here did not come from driving through anything.

• Blocked sunroof drains. The most common by far. Water backs up and runs down inside the pillars into the headlining and carpets.
• Blocked door drains. Doors are designed to let water in and drain it out of the bottom. Blocked with dust, it sits inside.
• A blocked air conditioning condensate drain, which puts water on the passenger carpet instead of the road.
• Perished window or windscreen seals, often after a glass replacement that was not sealed properly.
• Scuttle drains at the base of the windscreen, packed with dust and leaves.

If you have damp carpet and no flood, the drains are the first place to look, and clearing them is inexpensive.

Why the Damage Appears Later

This is what owners underestimate. A car that got wet and then dried out can seem entirely fine for weeks.

Electrical connectors

Modern cars have a great many multi-pin connectors, many of them low down: under seats, in door sills, under the dashboard.

Water gets into them and corrosion begins on the pins. It does not cause an immediate failure, it causes a gradual increase in resistance.

Weeks later you get intermittent faults that make no sense together, because several unrelated circuits are all degrading at once.

Modules

Control units are frequently mounted low, under seats or behind kick panels. A wet module may work initially and fail later.

Corrosion under the carpet

The underlay holds water against the floor pan for a long time, and corrosion works from the inside outward where nobody looks.

Smell and air quality

Damp underlay and a wet ventilation system produce microbial growth. Once established it is difficult to remove without stripping the interior.

What Proper Drying Involves

Blowing warm air into the cabin is not drying a car out.

1. Remove the carpets and underlay. Underlay is a sponge and it will not dry in place.
2. Remove seats where water reached them, since the foam holds water and seat modules sit underneath.
3. Dry the floor pan and check for corrosion starting.
4. Inspect and clean connectors in affected areas before corrosion establishes.
5. Address the ventilation system, since a wet evaporator and ducting will smell.
6. Find and fix the source, if it was drains rather than a flood.

That last point matters: drying a car without clearing the blocked drain means doing it again after the next wash.

Buying a Used Car: Spotting It

Water damage is one of the things a pre-purchase inspection specifically looks for, because it is hidden and consequential.

• A musty smell, particularly with the ventilation running.
• Damp or stained carpet, especially in the footwells and boot.
• Silt or fine dirt in seat rails, under the spare wheel and in crevices.
• Corrosion on connectors or bolt heads under the carpet or seats.
• Interior electrical faults that seem unrelated to each other.
• Mismatched or newer carpet in an otherwise older car.

See the pre-purchase inspection checklist.

Exotic Auto Services in Musaffah will assess water-affected cars and, importantly, find where the water came in.