RACQ Motoring

Flood damaged vehicle – repairs

Flooded carThis is a guide to the type of repairs a flood affected vehicle is likely to require. It also outlines the possible longer term effects inundation can have on a motor vehicle.

It is not intended to be a comprehensive list of all vehicle components, rather it is intended to provide guidance about the most commonly affected parts.

Insured - If your vehicle is insured, we strongly recommend your first action should be contacting your insurer for specific advice about what you need to do next.

Uninsured - If your vehicle is uninsured or not insured for this type of damage, you will need to decide on the best course of action for your particular circumstance.  You may need professional advice / assistance.

Uneconomical repairs

It is important to note that many vehicles that have been substantially inundated will be uneconomical to repair. As a guide, vehicles that have been immersed to a point where water has entered the interior are likely to fall into this category, though each case needs to be judged on its own merits.

If water has reached or covered the dash, the vehicle will almost certainly be beyond economical repair. Be aware though that the full extent of damage and required repairs may only become evident over time.

Salt water is very aggressive and causes much greater damage, has more long term implications than fresh water and is very much harder to deal with. However silt, mud and other material carried by fresh water can be difficult to remove and will increase repair difficulty and costs.

If your car has been flooded

Never attempt to start or drive a flooded vehicle until a thorough inspection and cleaning has been performed and any necessary repairs have been carried out.

Before attempting to start or drive a flooded vehicle:

  • Always check for debris in the engine compartment and under body, even if the water doesn’t appear to have been very high.
  • Also be aware that animals, reptiles and insects may have taken refuge in vehicles.  
  • Silt and mud can also carry contaminants that can cause infection.


Many of the checks listed below require an advanced level of mechanical understanding and may well be beyond the scope of a motorist’s DIY skills. As with any maintenance work on a vehicle, it’s important for your safety to only undertake work within your capabilities.

Determining if a vehicle can be salvaged

Any vehicle can be repaired if enough time and money is spent on it. However for the average car there are some definite limitations on the extent of repairs that can be carried out before the task becomes uneconomical.

  • A realistic assessment of the vehicle’s value, condition and the likely cost of repairs therefore needs to be carried out.
  • In most cases, if the water level has exceeded the lower edges of the doors and has made its way into the interior, it’s questionable if the vehicle will be economical to repair.
  • If the inundation is due to salt water, and it’s reached any more than about floor height, it will almost certainly be unviable to repair.

However for many people, in the short term at least, a wet car that runs and is safe to drive will be better than no car at all.

  1. Start by checking oils for contamination
    If you find that the levels appear very high i.e. engines, transmissions and diffs appear to be over-full, there is a fair chance that water has entered. This is because oil floats on water. Note also that there may be no obvious sign of water in the oils.
  2. Check for debris and in the vehicle compartments
    If there is nothing to suggest that water has entered mechanical components, have a general look around for debris that may have become trapped in the engine compartment and under body, and remove it as required. Watch also for wildlife that may have taken refuge in the vehicle, particularly in the cam belt area, and remove as necessary.
  3. Test the engine and brakes 
    If the engine can safely be started, try a short drive, test the brakes (at low speed first) and look and listen for any abnormalities. If nothing is evident, it’s probably okay to drive, however we recommend that you have it checked over by a mechanic.

If there is evidence that water has entered any of the vehicle’s components, the following information will guide you through the steps necessary to resolve the problem.

Electrical components

Immediate issues

Starters, alternators, wiper, window and other motors will rarely work immediately after being submerged. Sometimes they will begin working after they have dried out, however dismantling and cleaning or replacement may be necessary.

Electronic units and computers may be damaged by fresh water immersion however in some cases the components will operate satisfactorily after drying. Engine and power train control computers located in engine compartments are usually sealed and are therefore less likely to be damaged than those located in the passenger compartment. Salt water affected components are likely to be unrecoverable.

Long term issues

Electrical connections are prone to corrosion after immersion. This may not produce immediate problems however longer term reliability issues may develop. If possible separate electrical connectors and spray with a good quality water dispersant to provide protection against corrosion.

Repair of electrical equipment immersed in salt water may be impractical.

Batteries

Unless the battery is sealed it’s unlikely to survive being immersed. A replacement battery will most probably be required.

Engines, transmissions and final drives

The likelihood of damage to mechanical components depends on the type of water involved, the length of time submerged and how quickly the components were treated afterwards.

Engines that have been immersed in fresh water and treated quickly afterwards are likely to survive fairly well.

  • Drain contaminated oil and replace.
  • It’s probably also worth replacing the oil filter at this point.
  • Remove spark plugs and turn engine by hand to remove any water from cylinders. For diesel engines, please refer to a mechanic.
  • Check manifolds, air cleaners and ducting for water and drain if necessary before attempting to start the engine.
  • For engines with timing belts check to ensure silt, debris and animals / reptiles haven’t found their way inside timing belt covers. This could derail a timing belt and cause extensive engine damage.
  • Reassemble, start and run the engine as soon as possible to assist in the drying out process. Warning: Attend to the transmission before starting the engine.
  • Clean mud and silt from mechanical components by hosing. High pressure water blasters are effective for this purpose however they should not be used to clean radiators, air conditioning condensers or other fragile components.


When checking oil levels and contamination with the engine’s dipstick be aware that oil floats on water. Very over-full readings indicate the possibility of water contamination, even if there is no evidence of water on the dip stick.

Salt water affected engines are unlikely to be salvageable.

Manual transmissions

  • Drain contaminated oil and refill as soon as possible. Manual gearboxes immersed in salt water may not be salvageable.


Warning: Do not start the engine before attending to the transmission.

Automatic transmissions

Water causes de-lamination of clutch plates and bands. This may not be evident immediately, however flooded automatic transmissions are likely to require overhaul. The timeframe will depend on the amount of water, the extent of the exposure and the type of water involved.

When checking oil levels and contamination with the transmission’s dipstick be aware that oil floats on water. Very over-full readings can indicate the possibility of water contamination, even if there is no evidence of water on the dip stick.

Note that some automatic transmissions have a filler plug in the side of the transmission rather than a dip stick. It could be very much harder to check these for water contamination.

Warning: Do not start the engine before attending to the transmission.

Clutches

Clutches can become rusted onto flywheels after being wet. The clutch pedal operation will feel normal but you will not be able to select or change gears with the engine running.

Bringing the engine to full operating temperature will sometimes free the clutch. However if it refuses to release you should seek professional assistance.

Final drives

Remove filler plugs and check for the presence of water. An overfull diff could be an indication of water contamination. Drain and refill with correct oil. Differentials immersed in salt water may not be salvageable.

Wheel bearings

Water entry into wheel bearings will severely shorten their lives. Some wheel bearings are sealed and therefore cannot be cleaned and dried.  Serviceable wheel bearings should be cleaned, inspected and repacked with appropriate grease. Replace hub seals as well as these are probably the cause of water entry.

Steering systems

Drain and refill power steering systems if contaminated.

Fuel systems

Water in fuel will damage in-tank pumps so no attempt should be made to start a vehicle until you can verify that there is no water in the tank.

  • If water is present, drain and replace the fuel. Avoid ethanol fuels where water may be present as only a small amount of water is needed to cause the ethanol to drop out of suspension.
  • Diesel fuel systems are very sensitive to water contamination so extra care is needed to ensure there is no water in the system. Check water traps (if fitted) regularly.
  • It would be wise to replace fuel filters in both petrol and diesel powered vehicles.
  • Check air cleaners, duct work and manifolds for water and drain if necessary. Dry air cleaner elements or replace if contaminated with mud or silt.

Brake systems

Car in mudBrake fluid is hygroscopic, meaning that it absorbs moisture. Water contaminated brake fluid has a low boiling point which can cause rapid and unexpected loss of brakes under normal operating conditions.

  • Water contaminated brake fluid will also increase the risk of internal corrosion. Brake fluid must be flushed and replaced after any level of immersion.
  • Surface rust may form on brake discs and drums. However this is not generally a serious problem and will be worn off during the first few applications of the brakes.
  • Brake linings / pads may rust onto drums / discs if the hand brake was applied during the immersion. This will feel like the hand brake is jammed on, though in most cases it will free itself once the vehicle is driven. If it will not free itself, dismantling will be required.

Body structure

Clean mud and silt from the body as far as possible. Ensure body drain holes are clear to allow any water trapped inside panels to escape. Be aware that water immersion may result in long term rust problems.

Interior fittings and trims

It may be necessary to remove seats, carpets and trims to facilitate proper cleaning and drying. Dry the interior by opening doors and allowing air circulation to evaporate the water.

Note that many pressed metal components used inside vehicle cabins are not painted or have only thin protective coatings. This is particularly true of seat and under dash components. These may begin to rust after exposure to water. A protective spray of water dispersant may help, though many of these components will be difficult to access.  

The wet smell may be almost impossible to totally remove from the vehicle’s interior, even after cleaning.

Safety systems

Safety systems such as airbags and seat belt pre-tensioners may be adversely affected by water immersion.

  • Before the vehicle is put back into service it is strongly recommended that such systems be checked and tested by a mechanic with the right test equipment.
  • This will usually mean a visit to the dealer for the make involved.


Seat belt latches and retractors may not operate after immersion.

  • Seat belts will need to be replaced as they are not repairable.
  • Also be aware that dirt in the webbing of seatbelts can eventually weaken the webbing.
  • These comments apply equally to child restraints.

Lighting systems

Check operation of all lights before using the vehicle. It may be necessary to clean water, dirt and mud from inside light assemblies.

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The information provided in this fact sheet is intended as a general guide only. You should carry out further research and investigations into the topics outlined above prior to implementing any actions or recommendations