What Happens if Water Gets in Your Engine?

It doesn’t take a car expert to conclude that water doesn’t belong in your car engine. Water, fire, and electricity aren’t known to mix very well. Unfortunately, water does find its way into engines, especially in cars whose owners live in flood-prone areas.

If water gets in your engine, it can cause hydrolocking, which eventually leads to engine failure. Water in the engine can also cause oil, petrol, or transmission fluid contamination, electrical faults, or rust. These potential problems are very dangerous and can result in engine malfunctions.

Below, I’ll explain in detail how each spells disaster, and what you need to do to avoid engine damage if water gets in your motor.

What to do if water enters your engine.

Why Water in the Engine Causes Hydrolocking

Hydrolocking happens when water gets into the cylinders, causing engine failure.

Car engines burn fuel to generate the horsepower that drives the car forward. To optimize fuel combustion, pistons compress an air-fuel mixture inside the cylinders.

The air-fuel mixture is mostly gaseous, which pistons have little trouble compressing. Water, on the other hand, offers a stern resistance to compression.

If water gets in the cylinder, the crankshaft will turn the piston as usual, but the piston will find water instead of an air-fuel mixture. Manufacturers pack the pistons tightly in the cylinders to minimize energy wastage.

Therefore, the compressed water will have nowhere to go. However, the energy must go somewhere.

If you’re lucky, the engine will seize and stop. If you’re not so fortunate, parts of the combustion chamber may start flying off.

Powerful engines bend or break the connecting rods, causing them to blow holes in your engine.

Water gets in the cylinders through the car’s air intake. It can happen if you drive through a flooded section of road or if you wake up to find a river instead of your front street.

Therefore, if you’re unsure about the level of your air intake, avoid crossing a flooded section with your car. It doesn’t take a lot of water in your cylinders to hydrolock your engine.

A hydrolocked engine might resume operation after a lengthy and expensive rebuild. However, if the compression blew holes in your engine, start saving for another engine or car.

Water Can Contaminate Oil, Petrol, or Transmission Fluids

The sealants in your engine might let in water, especially if the car stays submerged in water for several hours.

Contaminated oil won’t cool or lubricate the car’s moving parts effectively if contaminated with water. You might not notice it immediately, but an engine with contaminated oil will cause damage to parts of the engine.

Before you ignite your car, check the oil dipstick. If you notice water droplets at the end, your oil needs draining and replacing.

To be safe, remove the oil pan and wash any mud that might have accumulated.

Contaminated transmission fluid can also destroy parts of your transmission. If you observe water on the transmission’s dipstick, have the fluid drained and replaced.

It’s rare to find a car built over the past couple of decades suffering from fuel contamination due to flooding. However, if your vehicle spent several hours submerged, it would be wise to check.

Simply drain the fuel from the tank and check for traces of water. If you find any, have the tank cleaned and replace the fuel filter.

Water Can Lead to Electrical Faults

Water and electricity rarely combine to good effect; therefore, flooding can cause significant damage to your engine’s electrical system. Car circuits are built to be water-tight, but the leads have to be bare.

Water-logged distributor caps won’t send electricity to the spark plugs. Water can also prevent electricity from reaching the spark plugs.

The engine’s fuse box is very susceptible to flooding. Fuses regulate the currents sent to various parts of the motor.

Water can damage the fuses leading to chaos inside your engine. It’s easy to tell when your fuse box gets contaminated with water as various engine functions will start malfunctioning.

Excessive Water Can Cause Your Engine To Rust

If water gets into your engine, the engine’s parts will likely start rusting. The effects of rusting vary depending on the location of water accumulation.

For instance, if you fail to remove the water in your fuel tank, a hole will develop in the fuel system due to rust.

The problem might come sooner if your car floods with salt water.

What To Do if Water Enters Your Engine

Water in your engine can cause serious problems, the worst of which is hydrolocking. If not looked after immediately, your engine and other systems may be irreparably damaged. Therefore, you need to know what to do if your engine floods with water.

At all costs, avoid driving through water if you believe that the water is too high but if at an unfortunate circumstance and water entered your engine, here’s what you should do:

  • Try to make it out of the water, and check if your car stalls immediately after. If it does, you have a hydrolocked engine. You’ll need a tow truck to get off the side of the road.
  • If you made it out of the water but the car hesitated before you crossed, find a place to park and let the engine’s temperature dry the vehicle. Check the brakes to ensure that they’re still working. After the car has cooled down, check if the oil, transmission fluid, or petrol are contaminated with water. If they are, drain and replace.

Don’t travel long distances without checking for water contamination. Refusing to check may cause more problems.

  • If you wake up to find your car flooded, start by checking the water level. Most experts state that if the water level reaches above your dashboard, call your insurance company to total the car. It likely means that your entire engine is flooded.

Correcting such damage requires a lot of time and a lot of money. The water level you observe might not be the maximum water level reached. Dirty water will leave a stain where it was highest.

  • If you are confident that water didn’t get into the cylinders, check whether the water contaminated the oil, transmission fluid, or petrol, and don’t start the engine. Begin by disconnecting the battery and check the oil and transmission fluid dipsticks. If they have water, drain the oil and transmission fluid and replace them with fresh fluids.

Drain the fuel tank and check for traces of water and have the fuel tank washed by a professional.

In the case of flooding, I recommend that you consult a professional before turning that car key. The next step is checking the electronics, and to do so, you might have to turn the engine on.

If the cylinders have water, the engine gets destroyed. So, before you proceed any further, consult a mechanic or insurance assessor, while waiting, dry any water that has gotten into your car. Water can cause rusting and encourage the growth of mold.

Use vacuum cleaners to get all the water out. Once confident that you’ve got all the water, open the doors and let the car aerate and dry. Be aware of any dampness you missed.


Water causes significant damage to your engine. In the worst cases, you might need a new engine due to hydrolocking.

In mild cases, you’ll contend with rust several years down the line so try as much as possible to avoid driving your car in water that might get into the air intake.

If flooding occurs, start by checking for signs of oil, petrol, and transmission fluid contamination, but wait for your mechanic before starting the car.

If flood water rises above the dashboard, pray that your insurance covers flood damage. It’s cheaper to call your insurance rather than a mechanic.



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