Hydrolocked Motor? This Is What You Need to Understand

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Marc Skirvin

Quick Tip

A hydrolocked motor occurs when water enters the engine's cylinders, preventing the pistons from moving and causing severe engine damage. This can happen if you drive through deep water or have a coolant or injector leak. If your engine hydrolocks, immediate action is crucial to minimize damage. Repairs can be costly, often making it more economical to scrap the car. Understanding hydrolocking and taking preventative measures can save you from hefty repair bills or the loss of your vehicle. If your car is beyond repair, consider selling it to a salvage service for its remaining value.

Pop quiz: what happens when you combine metal, fire and water?

Answer: Disaster.

If you’re new to internal combustion (or know nothing about cars), you may be tempted to speed through a large puddles. Sure, it’s thrilling to create your own waves…until your engine dies.

Unless you want to destroy your vehicle or pay some hefty repair bills, we recommend protecting your car from serious engine problems at all costs. Hydrolocked motors can also occur if car owners unwittingly put their vehicles at risk through a cold air intake system.

Understanding how a hydrolocked motor happens and what the results may be is vital to protecting your vehicle. Here’s a breakdown of what to do to avoid this and other serious engine problems.

What is a Hydrolocked Motor?

In simple terms, a hydrolocked motor is when your car’s engine fails. The official term is a hydrostatic lock. This has much to do with the fact that car engines work on internal combustion.

Internal combustion engines have a moving piston and a static cylinder. As the expanding gases produced by the combustion inside the engine expand, they push the piston.

This rotates the crankshaft. This sets the gears of the power train in motion and gets the wheels turning.

Because of this, a hydrolocked motor is no regular failure. When your engine takes on a huge amount of water into those cylinders, it undergoes a fatal failure or seizure. 

If your motor hydrolocks, you will hear loud crashing or banging sounds shortly before it stalls.

An internal combustion engine is basically an air pump. This means it’s designed to compress air. When water enters the cylinders, it’s nearly impossible to compress.

Because the molecules in water attract each other, they stay closer together than other liquid molecules. This leaves little to no room for those molecules to get any closer together.

A tremendous amount of pressure would be needed to compress water. Even if that pressure existed inside your car’s engine, the water would barely move.

When water gets inside your engine’s combustion chamber, the crankshaft rotation forces the pistons upward as it tries to compress the water. Because water is incompressible, the reaction force is greater than what your engine can deal with.

Sadly, in this situation, something’s gotta give…

If you have a small-capacity engine, it will stall. The engine’s force during the attempted reciprocation isn’t enough to deal with the water and you hear a grinding halt. 

Unfortunately, the resulting damage to many internal components usually means the death of your car.

Hydrolocking While Idling

Unfortunately, a hydrolocked engine can even happen if you’re idling. Sitting in standing water or driving slowly through it still poses a risk. Your engine doesn’t have to be rotating quickly to hydrolock.

The good news is, this is the lesser of the worst results due to a hydrolocked engine. Typically, the method for dealing with this degree of hydrolocking is to remove the spark plugs. You or your mechanic will then turn the engine over and flush the water out.

If you’re a novice at car repairs, do not try this on your own.

An experienced mechanic will know that the engine should be checked thoroughly. They should remove the inlet manifold and cylinder head.

This allows the mechanic to check for any other damage and to make sure no water remains. Again, the expenses for repairing a hydrolocked engine add up quickly with all your engine needs to recover (if recovery is possible).

If you’ve hydrolocked while idling and you are able to repair it, changing your engine gaskets will be necessary as well. The faster you can remove the water, the less likely your engine will corrode. 

The quicker your response time in caring for your motor, the less likely the damage will be fatal to your car.

Hydrolocking With Speed

Did you speed through that puddle? This is the worst degree of hydrolocking. Especially, if you have a large-capacity engine and you were driving fast.

Again, it’s those reaction forces from the large volumes of water that will destroy your internal components. Most often, it’s the connection rods that break.

The least damaging scenario is if the connection rods bend. When this happens, they must be replaced and you’re looking at an engine rebuild. While expensive, there’s still hope to save the car.

On the other hand, if the connection rods snap, a large piece of metal can move through the cylinders on its way to the crankcase. This results in serious damage.

Large holes are blasted through the sump or cylinder head. When this happens, you have two options as a car owner: pay for an engine replacement, or scrap the car.

Avoiding Hydrolocking: Causes

The number one greatest cause of a hydrolocked motor is driving through deep puddles or flood waters. If you’ve never been warned against this, the reasons extend beyond hydrolocking your motor. Deep waters can also damage your electrical components or undercarriage.

Other components that can be hurt by water include:

  • CV joint boots
  • Tie rods
  • Ball joints
  • Airbag system
  • Wiring
  • Wheel bearings
  • Shocks
  • Brakes

While driving through very high water is the most common cause of a hydrolocked engine, there are other dangers that can cause engine problems.

Cold Air Intake Placement

Some inexperienced mechanics or car owners make vehicle modifications that place the intake system in a dangerous place.

They may try to find a different place for the cold air intake. Often, novices will install a cone air filter low in the corner of their bumper. With such a low location, the engine is in severe danger while driving through even bumper-height waters.

Large puddles or floods are no longer the only enemies; even small rain showers can be a potential threat to the engine.

Coolant Leaks

Another risk of hydrolocking comes in the form of coolant leaking into the pistons. This causes head gasket failure which leads to a hydrolocked motor.

Most of the time, head gaskets fail when thermal expansion occurs too quickly for the gasket to handle. This creates ruptures. The level of severity varies, but any time a head gasket separates the cylinders and coolant passages, your engine will hydrolock.

Injector Leaks

The last, and most rare, cause of a hydrolocked engine is an injector leak. If your injector becomes cracked or stuck, fuel can flood in. Adam LZ, the racer and used-car enthusiast, recently experienced this very thing.

Still, if it happens, the best repair method is to flush the fuel from your intercooler, cylinders, and intake manifold.

Suspect Hydrolocking? What to Do Next

The hard truth is, with a hydrolocked motor, you’re either looking at some painful expenses or having to scrap your car entirely. Most vehicles that undergo “flood damage” are totaled.

If the vehicle is salvageable, you’re looking at an average of around $2,500-$8,000 in repairs. For many car owners, this may be more than the value of the vehicle itself.

Understanding what causes these types of engine problems will empower you to make the most financially wise choice.

Research your car’s internal components. Knowledge is power, especially when it comes to extending the life of your vehicle.

If you suspect your motor is hydrolocked, the next step is to find an excellent mechanic. The problems arising from this issue can be complex and experience is key in selecting a mechanic who can properly diagnose the severity of the damage.

Avoid being taken advantage of by untrustworthy mechanics by reviewing this guide. Get a firm grasp on how hydrolocking affects the inner workings of your car’s engine.

Don’t be afraid to seek a second opinion. If you are in love with your car, it may be worth having more than one expert take a look.

The Worst Case Scenario: It’s Unsalvageable

Unfortunately, there is little that’s worse for your car than a hydrolocked motor. If you’re certain nothing can be done to restore your vehicle, all is not lost.

Our team of professionals is here to help you. Contact us today at Cash Auto Salvage for a quote on the value of your vehicle. No matter the condition of your car, we will buy it. 

Turn lemons (see what we did there), into lemonade, and don’t let your vehicle’s sale potential go unmet. While it’s never fun to lose a car to a hydrolocked motor, Cash Auto Salvage can help you find a silver lining.

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About the Author

Picture of Marc

Marc is the Co-Founder of Cash Auto Salvage and Director of daily operations. He retired from a leading Internet Marketing company in 2013 and has been involved in the automotive industry ever since.

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