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Avoiding a Flooded Engine: Keep Calm Driving In Wet Weather

Man pushes flooded car through deep water.

It’s the stuff of nightmares: You’re driving through a puddle that turns out to be much deeper than you thought. Before you know it, you find yourself running the risk of a flooded engine. Whether you’re caught by surprise in a sudden rainstorm that turns the street into a swimming pool or come across a washed-out section of road with a creek flowing across it, it’s never a good idea to expose your car to deep water. The best course of action is to avoid driving through water at all, but sometimes a situation may take you by surprise. A flooded road may hide a washed out hole that is much deeper than it looks. Here’s how to deal with an unexpected automotive aquatic experience.

Don’t Panic

These tips apply no matter if you are driving a subcompact or a massive SUV, as neither are immune to the force of water. If you find yourself driving through water past the point of no return, don’t panic. There are a few things you can do to avoid a flooded engine. The first, and most obvious, is to shut off the ignition, but only if it is absolutely safe to do so. If, for instance, you find yourself in the middle of a deep parking lot puddle of still water, you can switch the car off immediately and call a tow truck or push the vehicle out manually, if you’re particularly brave. Once the vehicle is out of the puddle you can check for any water intrusion in the interior and take any steps to dry it out.

A red wagon drives through a flooded street.If, on the other hand, you happen to be driving through water with a strong current on a roadway, it’s safer for you to forget about potential engine damage, put the car in reverse and attempt to back out of harm’s way immediately. Flowing water is powerful and all it takes is 12 inches of moving water to push your vehicle off the road. If the car stalls while still in the water, get out and climb on the roof to wait for help.

Regardless of whether you decide to back up or keep pushing forward, make sure you do so at a slow, steady speed. Driving quickly through standing water is a great way to generate a wave of liquid under your car that can enter into your engine bay and wreak havoc. A minor inconvenience puddle traversed at slow speed could turn into major engine destruction if too much water gets splashed up.

Determine If Water Entered Your Engine

The most common way water damages a car’s engine is when it gets sucked up through the air intake. The air intake is designed to draw in air from a protected location, but it is not a snorkel. Commonly the air enters from behind the headlights or above the radiator. Both are key locations that can get hit with water when driving through water. When too much water is introduced into your motor’s cylinders it results in hydrostatic lock, or “hydrolock,” an engine state in which the pistons freeze and the engine stalls. Water does not compress like air which is what causes the sudden stop. This sudden stoppage can irreversibly damage internal components (bend rods, shatters pistons) and turn your car’s motor into little more than a glorified paperweight. And it can happen in a flash.

Although it takes a fair amount of water to cause hydrolock, remember that even small amounts of moisture inside your motor can cause it to stall. The easiest way to quickly decide whether your engine sucked in any water or not is to locate the car’s air intake once you’ve reached safety. If there’s noticeable moisture high up in the engine bay, above the depth of the water, then you likely have nothing to worry about; if there’s evidence of moisture penetration down low, such as beneath or near the bumper, then you have cause for concern, especially if your vehicle was submerged significantly at any point. You can also check your air filter for signs of water damage.

Take It to a Mechanic

Is your car sputtering or acting funny after driving through water? Even if your engine is still running after your watery encounter, if you suspect that your intake might have sucked in any water, it’s a good idea to get things checked out by your local NAPA AutoCare Center. In doing so, you can also determine if any of your car’s electrical components, such as bulbs, wiring or sensors, need to be replaced after being waterlogged. Depending on the level of water encountered you may need to have the oil, transmission fluid, even axle oil checked for water contamination.

Check out all the tools & equipment available on NAPAOnline or trust one of our 17,000 NAPA AutoCare locations for routine maintenance and repairs. For more information on caring for flooded engines, chat with a knowledgeable expert at your local NAPA Auto Parts store.

Image courtesy of Wikimedia Commons.

Benjamin Hunting View All

Having been bitten by the car bug at a young age, I spent my formative years surrounded by Studebakers at car shows across Quebec and the northeastern United States. Over ten years of racing, restoring, and obsessing over automobiles lead me to balance science writing and automotive journalism full time.  I currently contribute as an editor to several online and print automotive publications, and I also write and consult for the pharmaceutical and medical device industry.

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