Floodwater: How it Can Damage Your Vehicle

Everybody knows the saying; “If it’s flooded, forget it!” However, apart from the potentially life-threatening danger to driver & passenger/s by becoming trapped or washed away, there is also the very real possibility of damage to your vehicle. It is advised that to drive through floodwater, the level should be no higher than more than half the height of the tyre. However, looks can be deceiving when it comes to water levels, & even a relatively small amount of water can significantly damage your engine. Water can be sucked into your engine via the air intake system. Even if you think your vehicle can handle it & you’ve witnessed similar vehicles seemingly drive through unscathed, something unexpected & seemingly insignificant as a passing vehicle can cause a ‘wave’ of water that can be ‘swallowed’ into the engine. Nevertheless, if you do decide to take the risk to drive through floodwater, or your vehicle is affected by rising water levels, there are some things to consider before continuing to drive your vehicle.

Below are some components of your vehicle that can be affected, how damage can occur & signs to look for afterwards.

The Engine

Even if floodwater looks shallow enough to drive through, water can still be sucked up into the air intake system (as it is close to the ground) & enter into the engine cylinders. Inside these cylinders, pistons compress air. When they are filled with water, the water can’t compress & this causes the pistons to seize, instantly stalling the vehicle in what is called ‘hydro locking’. Sometimes, this is irreversible. The most important thing to remember is if your car ‘hydro-locks’, do not try to re-start your vehicle as that could cause more water to enter the engine, causing even further damage. In a life-threatening situation, your life is obviously more important than any potential damage to your engine, & you may need to try to re-start your car. However, if it is only standing water, it is best to wait until the water recedes & then call your local mobile mechanic or have your vehicle towed to their workshop when it is safe to do so.

Once water enters your engine it can also cause damage & rust, especially from typically salt-heavy flood waters. The water can also cause cracked rings, bent piston rods, or crack the engine block. If the water is at a high enough level that the exhaust pipe is flooded, the engine will not be able to ‘breathe’, thus also stalling the vehicle.

Even if your vehicle makes it through the water, if you feel your engine starts spluttering, making strange noises, is running ‘rough’, or you experience a sudden loss of power, these are signs of a flooded engine.  All of these factors are serious & can be potentially expensive issues.


If your vehicle has disc brakes they will most likely work immediately, but you should still test them as soon as possible after driving through flood water by ‘pumping’ them. Doing so will cause the brake pad to rub against the disc, helping to wipe off any excess water. However, dirt & residue in the brakes can inhibit optimal performance.

During normal driving conditions, brake rotors & disc pads can reach temperatures as high as 200 degrees Celsius. When driving through water, especially if it is colder water, the sudden change in temperature can cause your rotors to warp & disc pads to crack, resulting in them wearing out quicker. You will notice the brakes have been compromised if you feel a vibration or unusual sounds when applying the brakes when driving. Water in brake drums may also not be evident until much later.

Fluids (Engine Oil, Transmission oil and Differential fluid)

Driving through deep water can cause water to enter the engine compartment & contaminate the essential fluids such as engine oil. Driving with contaminated & watered-down fluids can cause serious damage to the engine. If you suspect water contamination, contact your mobile mechanic or get towed to their workshop for a vehicle inspection.

To check the condition of the fluids, pull out the dipsticks for the engine oil & transmission fluid. If the fluid looks milky, has changed colour, or there is a whitish substance under the oil filler cap (often referred to as ‘mayonnaise’) these are all signs the fluids have been tainted with floodwater & your vehicle needs to be examined by an experienced technician. Usually at the very least the oil & oil filters will need to be replaced.

Electronic Systems

Modern vehicles rely heavily on many electrical components & sensors, most of which are susceptible to short-circuiting when subjected to high water levels. Many manufacturers install automobile computers in the floor and under the seats, which are obviously lower to the ground & therefore more susceptible to flood water.

Electrical components on vehicles include; power steering, electrically powered windows & door locks, hand brakes, transmission control module, air conditioning, heated seats, rear camera, sunroof controls, windshield wipers, seat controls, parking sensors, headlights & indicators.

If any of these systems are not working properly, your engine is misfiring, or a warning light appears on your dash when the engine is running, it indicates water damage & your vehicle will need to be checked out by a mechanic.


Driving your vehicle though deep floodwaters can cause water to flow over the transmission & into the vent. Once water is inside, it can cause the gears to slip, & can dissolve the transmission’s lubricant, which can severely impact the transmission’s integrity.


Most modern vehicles’ suspension joints will not need to be re-lubricated after factory assembly. However, driving through deep water can strip this lubrication & cause early rusting, sometimes causing failure a long time after the initial incident. Because of this, it is highly recommended to have your suspension joints inspected and lubricated by a technician.


Driving through deep water can also cause corroding of your car’s battery terminals; thereby affecting the vehicle’s ability to start.


Even if you don’t think other components of your vehicle have been affected, one small way to tell that maybe water has indeed penetrated your car is to turn your heating on. Any water trapped in the heating & ventilation system will produce excess condensation on the windows inside the cabin.


When floodwater is deep enough, it can enter the cabin & ruin the carpet & upholstery. If floor carpets are damp, it’s a sign that other elements have probably also been exposed to flood water & need to be inspected by a professional. It is also worth checking the boot & spare tyre at this point.

Leaving the carpets & interior to air dry can cause mould & mildew to grow, which can be a health hazard & will also create an unpleasant smell. They usually require a professional clean which may require the use of a dehumidifier.

Apart from the risk of mould, components like seat brackets are prone to rust or malfunction if they are allowed to remain damp.

Underneath the Vehicle

After driving through floodwater, there is a strong possibility that there is mud, salt, dirt & debris stuck to the underside of your vehicle. These elements if left on for long periods of time can corrode the metal surfaces. It is recommended to hose off & clean as soon as possible.

When to contact your mechanic:

  • Your engine stalled when driving through water
  • You hear abnormal noises
  • Any of your electrical systems are not working properly
  • There is engine misfire
  • The engine sounds ‘rough’
  • The fuel warning light on the dash comes on
  • The vehicle is blowing white smoke
  • The engine warning light comes on
  • If you have any concerns after experiencing floodwaters

Remember, the damage caused by a flooded vehicle is not always immediately apparent. It is always better to be safe than sorry & contact a qualified technician to perform a vehicle inspection.

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If you notice any unusual symptoms or have any issues with your vehicle; contact one of our friendly, qualified technicians today on 0412 161 776 for a vehicle inspection. Don’t forget to like our  Facebook page for handy hints, information and special offers.