• There are already an estimated 400,000 cars being driven today that are damaged from past flooding.
• Floodwaters can destroy electronics, lubricants and mechanical systems in vehicles, problems that aren't apparent now but can show up down the road.
• Be sure to research the car's history, as well as search for signs of water damage in the vehicle itself.

If you're planning to shop for a used car in the next few months, be sure to check for flood damage before signing on the dotted line.

In the wake of widespread flooding across Florida, North Carolina and South Carolina last month due to Hurricane Ian, vehicle history report website Carfax now estimates that up to 358,000 autos were damaged by floodwaters. Some of these vehicles will end up being resold, as an estimated 400,000 water-damaged cars are currently on the road from past flooding events.

"Floodwaters cause all sorts of hidden damage, which can surface months later," said Teresa Murray, consumer watchdog with the U.S. Public Interest Research Group Education Fund. 

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"You don't want anything to do with a flooded vehicle, no matter whether the damage is disclosed and no matter what assurances you get from a seller," Murray said.

Flooded cars are 'rotting from the inside out'

Floodwaters can destroy — sometimes slowly — electronics, lubricants and mechanical systems in vehicles. Corrosion can eventually find its way to the car's vital electronics, including airbag controllers.

"The bottom line on these flood-damaged vehicles is they are literally rotting from the inside out," said Emilie Voss, spokesperson for Carfax.

"They might look fine cosmetically, but there can be mechanical, electrical, safety and health issues that will show up down the road," Voss said.

Buyers should research a used car's vehicle history report to make sure they know what they are buying, regardless of when or where they make the purchase, because flooded cars often end up for sale in places far from where they originally were damaged.

Through services like Carfax or the National Insurance Crime Bureau's VINCheck, you can input a car's vehicle identification number, or VIN, and see if there's anything in its history that's a red flag. However, those efforts alone may not be conclusive. 

Not all titles will reflect flood damage

That's because not all flooded cars are recorded as such unless an insurance company is involved. When an insurer receives a claim and the vehicle is totaled — meaning the repairs would cost more than the car's worth — the car's title generally is changed to reflect its status.

Those ruined cars are typically sold at salvage auctions to junkyards and vehicle rebuilders. Reselling them to consumers can get on the right side of the law if the title discloses the flood damage.

But not all car owners file an insurance claim. If they don't have comprehensive coverage — the part of car insurance that flooding would fall under — they're generally out of luck when it comes to coverage. So, with no insurance company involvement there may not be any official record of the flood damage.

"If you suspect a vehicle may have sustained flood damage, move on," Murray said.

There are things you can look for in a used vehicle for that could suggest flood damage, according to Carfax:

• A musty odor in the interior, which sellers sometimes try to cover with a strong air-freshener;
• Upholstery or carpeting that may be loose, new, stained or that doesn't match the rest of the interior;
• Damp carpets;
• Rust around doors, under the dashboard, on the pedals or inside the hood and trunk latches;
• Mud or silt in the glove compartment or under the seats;
• Brittle wires under the dashboard;
• Fog or moisture beads in the interior lights, exterior lights or instrument panel.