How to Spot a Flood Damaged Car Before You Buy

Flood damage hides in the places water could not drain from and in the trim that had to come out to dry the car. Lift the boot floor and look for silt in the spare wheel well, peel back a corner of the carpet and squeeze the underlay, run a hand along the bare metal seat rails feeling for rust, and get into a car that has been shut overnight and smell it before the seller opens a window.

Quick answer

Six signs give a flooded car away. Any one on its own can be innocent. Two or three together mean walk.

• Carpet or underlay that is damp, stained, oddly new or a slightly different shade to the rest of the interior.
• Fine dried silt or a mud tide line in the spare wheel well, along the seat rails, inside the seatbelt reel or under the boot side trim.
• Surface rust on unpainted metal that should never get wet, such as seat frames, bolt heads under the carpet, the pedal box and boot floor brackets.
• A musty cellar smell, or an interior soaked in air freshener to bury one.
• A tide mark, silt line or trapped moisture inside a headlight or tail light.
• Electrical faults that come and go, especially in things mounted low in the car.

Why flood damage is worse than it looks

A car is not sealed. Water that reaches the carpet also reaches wiring connectors, earth points, control modules and seat foam, and it carries silt with it. Once inside a loom, water wicks along the copper strands under the insulation and corrodes the wire where you cannot see it. Faults then appear weeks or months after the car looks and smells fine.

The expensive parts are usually mounted low. Airbag control modules sit under the centre console or beneath a seat, body control modules and fuse boxes live in footwells, and amplifiers are often bolted under seats or in the boot floor. Salt water and floodwater carrying sewage are far more destructive than clean rainwater, because the residue keeps attracting moisture long after the car has dried.

This is also a safety question rather than a comfort one. Corroded connectors in an airbag or seatbelt pretensioner circuit are not a fault you find out about on a test drive.

The write off marker is the reliable trail

When a flooded car is insured and claimed, the insurer's engineer assesses it and applies a salvage category, and that category is recorded against the registration for the rest of the car's life.

• Cat A: scrap only, nothing may be reused. Complete submersion, particularly in salt water, is one of the reasons a car ends up here.
• Cat B: the shell must be destroyed, although parts can be reclaimed. A common outcome for a properly flooded car.
• Cat S: structural damage that can be repaired. Water sitting long enough to attack structural members can land a car here.
• Cat N: non structural damage, which is where lighter water and electrical damage tends to sit. It can legally return to the road.

An accident history check returns any write off marker recorded against the registration, with the category and the date it was applied. A write off check covers the same ground, and if you want to understand what each letter allows before you view a car, read the guide to Cat A, B, S and N categories. A car advertised for the road with a Cat B marker against it should end the conversation.

Not every flood car carries a marker

Be realistic about what the record can do. A marker only exists if an insurer settled a claim, so plenty of flooded cars never get one.

• No claim was made: an older car on third party cover, or one worth less than the excess, gets dried out in a driveway and sold on.
• The claim was withdrawn: some owners take a look at the effect on their premium and repair privately instead.
• It arrived from abroad: a car flooded overseas and then imported does not always carry its foreign history with it. An import check at least tells you the car came in from another market, which is a reason to look much harder.
• It was never a flood at all: a leaking screen seal or a blocked bulkhead drain leaves the same damp carpet and corrosion, and it is just as expensive.

So run the check, then inspect the car anyway. The record tells you what was declared. The car tells you what happened.

Electrical gremlins are the giveaway

Test everything, and do it on a genuinely cold start rather than a car the seller has warmed up and left running.

Work every window, mirror, seat motor, heated seat, central locking button, interior light, wiper setting, indicator, sunroof, boot release and infotainment function. Watch the dashboard as the ignition comes on. Warning lights should all illuminate then go out, and an airbag light that never appears can mean the bulb was removed to hide a fault. Faults that appear once, clear themselves and return later in the drive are typical of corrosion rather than a single dead component.

Is a flood damaged car worth buying?

Sometimes, on three conditions. You know it is one, the price reflects it properly rather than shaving a few hundred pounds off the going rate, and the repair was done by someone who replaced the affected wiring and modules rather than shampooing the carpets.

Weigh the rest honestly. Some insurers refuse to cover a car with a salvage marker and others load the premium, some lenders will not finance one, and the next buyer will run the same check you did. Any manufacturer warranty is gone. Corrosion that started in a flood does not stop. A repaired Cat N with a full record of what was replaced and a genuinely low price can work as a cheap second car. A shell that should have been destroyed is a different matter, and it is worth reporting rather than passing on.