How to Properly Treat an Engine Damaged by Water

Every time you see a story on the news about a flooded parking lot full of cars, you thank your lucky star that it wasn’t your car. But here’s the thing about luck: if you wait long enough, it will eventually run out and your turn will come.

When it does, it’s best to be prepared. All isn’t necessarily lost when your engine gets water-damaged. If you follow the right steps, that is.

Here’s what to do in the event that your engine gets damaged by water.

Evaluate the situation

From the outside, the situation may look very grim. Your car could have been completely submerged in water. But don’t freak out just yet. Inside could be a different story. Modern engines are so tightly built that it’s possible that the engine didn’t take on any water at all. Seems like it would be a miracle, but it’s definitely possible, so don’t panic.

DO NOT try to start the engine before you do a thorough assessment. If there’s any water in the chamber, it’ll most likely damage a piston or connecting rod when you turn the ignition. This is called an hydrolock and it’s the kiss of death for your engine.

If you aren’t sure how flooded things got, look for a dirty water line on your car. If it seems that the flood water reached below the doors, your engine is probably fine. Just let the underside dry out before trying to star the engine.

If the water line reaches the top of the wheel rim, it’s possible that the engine is water damaged.

Now, if you happen to know that your car’s hood was completely submerged, things are pretty serious. Depending on your car model, water may have flooded the entire engine.

Where to look for water-damage

First, check the air filter and intake. If those are wet, it’s safe to assume for the worst. Look for other places where water could have leaked inside the engine.

Next, check the oil dipstick. If you see that there’s more oil than there should be, or if it looks milky, then you probably have water in the crankcase. The rear main seal wasn’t designed to keep water out (just oil in).

You can also check for water in other fluids, like coolant, power steering, and fuel systems. Disconnect the fuel line and drain it into a pan. If you’re seeing water, drain the tank and lines, and then replace the fuel filter.

If you really want to go the extra mile, and if you have the required equipment, send an inspection camera into the engine’s cylinders. You may see some humidity, and that’s okay. What’s not okay is standing water in the combustion chamber.

Getting water out of the engine

Now that the engine is on dry land, it’s time to dry it from the inside out. But there’s a right way and a wrong way to do this, so be sure to follow the steps in the right order.

Disconnect the battery (ground then positive cable) and set it aside. Remove plastic engine covers and dry all exposed areas of the engine with shop towels.

Method #1:

Remove the spark plugs and crank the engine by hand. Keep rotating the crank until the pistons are at Top-Dead-Center (when the piston #1 is as high as it can go in the cylinder). This way, you should either be able to reach the water with a towel or a shop vac. Do the same for all cylinders. Get as much of it as you can, but understand that it’s not possible to get every drop this way. Do your best and that should be enough. If you run the shop-vac over the plug holes, this may help get some extra water out.

Method #2:

Remove the spark plugs, disconnect the fuel injectors and turn the key to crank the engine. With just a few revolutions, you should be able to clear all the water through the spark plug holes. After that, change the oil and filters. Be sure to change the oil again in about 500 miles or so just to be safe.

Replace all fuses and check the air filter and intake ducting to look for signs of water.

Now, it’s time to take care of your transmission. It’s even more susceptible to water damage than the engine actually. Drop the pan and replace the oil and filter. Then, keep an eye on how it’s running to see whether there could be more damage. If the flood reached your differential, replace the differential fluid too.

When to call it quits

Some cases are simply beyond repair. Even the most skilled auto mechanics can’t save every water-damaged vehicle without it costing an arm and a leg. Classics are even more susceptible to water damage because there are more ways for the water to get into the engine and the replacement parts are significantly more expensive. Newer vehicles, on the other hand, are equipped with more wires and complex sensors that aren’t designed to get wet.

Still, if you have your heart set on fixing an extremely water-damaged car, know that it’s going to be a labor of love – that will also get quite expensive. In most cases, when the engine has been flooded, it’s time to start talking to your insurance company about the possibility of totaling the vehicle.

Even if you spend your life savings restoring a flooded engine, you’ll probably find that it will never run quite like it used to. This is pretty common among flooded vehicles because there are so many possibilities for failure. And, no matter how it’s done, you need to understand that maintenance is going to become more important than ever. Be sure to follow the recommended service intervals outlined in your car’s repair manual to keep it on the road for years to come.