Driving through flooded roads can be very dangerous, and unless you have no choice, we highly recommend that you avoid driving during torrential downpours. If you are already driving, park wherever possible to avoid the water. In light of the flood that took place in Orchard on the 16th of June 2010, we feel it is always good to know what precautions to take when driving through a flooded road, and what damage it may cause your car.

First of all, muddy flood waters can hide obstacles such as curbs, holes, or any foreign objects that were swept away by the current, all of which can damage your car or get you stuck in the middle of the water. Try to drive in the centre of the road, as the water level will be the lowest there (roads are always slightly lower on the sides and higher in the middle to help rain water exit by the side drains)

Know that 15 centimetres of water reaches the bottom of most passenger cars, which can cause loss of control of the vehicle since it will start to float, and may also stall your engine, damaging it. In any case, do not drive in water levels higher than 25 centimetres (an easy way of measuring this is to notice if the water level reaches the centre of the wheels) as the chances of drowning the air intake will increase dramatically, causing major damage to your engine internals. Water might also reach the electronics, further increasing the repair bills.

The best way to drive through a drowned road is to stay in low gear (1st or 2nd), and move slowly, as increased speed will create a bow wave that risks backwashing in the air intake. For the same reason, don’t drive against approaching moving vehicles as the ripple wave they will cause will drown your engine.

The best way to avoid stalling and damaging your engine is, with manual cars, to slip the clutch and keep the RPMs high. On an automatic car, stay on the accelerator to maintain high revs, and keep a foot on the brake to control your speed. This method will also allow for the engine to keep running if the electronics are drowned. In any case, if the engine stalls, do not try to restart it; when cutting, the engine will cause a depression in the exhaust, sucking water into the engine. Shifting gears when the exhaust is submerged will have the same result, so if you are driving a manual, stick to the gear you are in until you drive out of the flood. After driving out of the water, make sure you test your brakes, as being submerged will make them slippery and less efficient.

When it comes to the engine, water getting in the combustion chambers, either through the drowned air intake or because of a backwash in the exhaust, will cause extensive damage. Whatever you do, do not try to restart the engine. It is safer and cheaper to have the car hauled to a mechanic shop where the spark plugs and injectors will be removed to let the water drain out of the engine block.

Another expensive item that can be added to your bill is the catalytic converter (also known as “cat”). This part of the exhaust operates at high temperature to block carbon monoxide and other environmentally unfriendly gasses from being released in the atmosphere. The difference in temperature between the cold flood water and the cat causes it to crack at the welds, and this can only be fixed by being replaced, at a high price.

On a last note, if the flood hits your car when it was parked, don’t start the engine, and follow the same procedures as when you stall while driving through water: let a professional drain the engine, it will save you an expensive repair bill.