Ask anyone about “car flood damage repair,” and most will say it’s impossible. Even car insurance companies, known to avoid spending money, tend to simply write off a flood-damaged car. Since cars are complex machines and flood water is harmful to all modern cars’ systems, the answer is usually not a simple one. Hydro-locked engines, short-circuiting electronics and water-logged transmissions are just a few potential results of water damage, not to mention mold, mildew and rust. Flood damage repair can fall into two categories, which can best be expressed as “economical” and “uneconomical.”
When cars get hit by a storm surge or river flooding, they may sit for days or weeks while water saturates everything. This can severely compromise your vehicle’s interior, electronics and powertrain. Salt water flooding, even light flooding, does the worst damage to cars. In fact, some experts consider a salt water flooded modern car to be unfixable at any level. Unless you are prepared to completely rebuild the car from the ground up, you should write off repairing a salt-water or long-term flooded car. Corrosive salt water can seep into chassis cavities causing rust that may never been seen until it is far too late. Even if you do get it running again, it is highly likely to have continuous issues that would likely far exceed the value of the vehicle over time. If your automobile spent a few days as a submarine, it is best to just write it off and move on.
Economical Car Flood Damage Repair
Your repair options depend on the extent of the flooding, water type, depth and duration of submersion. Fresh water isn’t as corrosive as salt water, so you might be able to repair a car caught in a river flood. If you drove into a flooded road and the engine died, you might be able to repair the damages. Here’s a list of tips and things to check in the event of flooding:
- Do not attempt to start an engine that has been flooded. A hydro-locked engine, if it even starts, will quickly destroy itself. If the oil level is abnormally high, water probably got into the crankcase because oil floats on water, making it useless as a lubricant. Disconnect the battery. Remove the spark plugs and turn the engine over by hand via the crankshaft balancer to force water out of the cylinders. Blowing compressed air into the spark plug holes and intake also helps (wear eye protection). Make sure to drain the oil and replace the oil filter, and then again around 500 miles after you get the vehicle back on the road.
- Check transmission fluid levels, as well as the transfer case and differentials, as these may also have been flooded. Often these components have breathers that allow air in and out, but will also let water enter when submerged. Automatic transmission discs and bands tend to delaminate in water. Manual transmission synchronizers can be ruined by lack of lubrication, and a soaked clutch may rust to the flywheel. Transmission problems may be allayed by completely draining fluids and refilling, and the clutch may release once you get the engine up to temperature. Differentials can hold a surprising amount of water if the axle tubes are also water logged. If there is water in the differential you will need to not only replace the gear oil but also re-pack all the bearings (included the wheel bearings).
- Paper filters like the engine air filter and cabin air filter will need to be replaced.
- Pay special attention to safety systems, such as water-contaminated brake fluid or power steering fluid. Water-logged brake fluid, for example, can vaporize leading to a loss of braking power. Flush the brake system and power steering system thoroughly using plenty of new fluid. Brake pads and shoes may spread rust to rotors and drums, but moving the car may free them.
- Dry out the car by removing the seats, carpets and insulation completely. Use a wet/dry vacuum to remove any remaining puddles while also checking nooks and crannies for water. Park the car outside on a sunny day, doors and windows open, and lay everything out in the sun — don’t forget the trunk. Mold is the enemy and can take hold nearly anywhere, so give everything a deep clean with mold/mildew remover. Disconnect all electrical connectors and dry them out with a hair dryer or heat gun. Any corrosion on the electrical connectors will need to be carefully removed with a wire brush.
- Depending on the level of flooding, you may need to drain the fuel tank to eliminate water contamination. Check with your local laws for the proper disposal procedure of contaminated fuel, never dump it out on the ground. You should also flush the entire fuel system and replace the fuel filter.
- Flood damage repair to electric vehicles can be summed up as: it depends. Luckily most automakers have designed their electric motors and battery packs to be waterproof. That’s good because the stuff inside those battery packs tends to burst into flame when exposed to water. But the electrical connections, wiring, modules, and other electrical components may not be as robust. Once past the drivetrain differences, problems with a flooded EV are similar to those of a flooded gas/diesel powered vehicle.
- After any flood damage repair of a 1996 or newer vehicle do a complete OBD scan. Check for pending faults and trouble codes. Sensors can be damaged by water and may need to be replaced.
In general, repairing flood damage is an uncertain venture. Be thorough and patient. Time is of the essence; drying your car out as quickly as possible will give you the best chance at successfully rescuing your ride.
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Ben has been taking things apart since he was 5, and putting them back together again since he was 8. After dabbling in DIY repairs at home and on the farm, he found his calling in the CGCC Automobile Repair program. After he held his ASE CMAT for 10 years, Ben decided he needed a change. Now, he writes on automotive topics across the web and around the world, including new automotive technology, transportation legislation, emissions, fuel economy and auto repair.