What is hydrolocking an engine

Aspiration is that coughing and choking feeling you get when food or liquid goes down “the wrong pipe.”

Something similar also occurs if too much water enters your engine, it’s called hydrolock, and it can cripple your car!

What is a hydrolocked engine, and how do you fix it?

Engine pistons are designed to compress a mixture of air and fuel – not water. Because of this, if enough water enters the cylinder, it may hydrolock, meaning they all stop moving at once.

Much of the resulting damage depends on how fast you were going when it happened.

Thankfully, this guide will explain everything you need to know about a hydrolocked engine. This also includes what prompts an engine to hydro lock, if it can cause damage, and how to fix it.

Are you ready to get started?

Let’s dive right in!

What Causes An Engine to Hydrolock?

The actual term is Hydrostatic Lock, which has been shortened to hydrolock. This happens when too much water enters the combustion chamber. When a piston reaches the top of its travel range, if the volume of water inside is more than the amount of space left, hydrolock will occur.

Why? Because water is less compressible than the air/fuel mixture inside. So, when the piston attempts to compress it, all of the cylinders will stop at once.

This will result in crashing or knocking sounds inside the engine that will last several seconds, followed by it shutting down.

What kind of situation can result in water entering the cylinders? There are many examples, like driving in a downpour or going through a deep puddle. This is one of the reasons that flood-damaged vehicles are often totaled afterward.

It’s also possible for the hydro lock to occur from other liquids, like oil or coolant. However, keep in mind that if this happens, it likely means you have a severe issue inside your engine, like a blown head gasket or a crack in the block.

Does Hydrolocking Harm An Engine?

Hydrolock can be very harmful to an engine and may require its replacement entirely. However, the speed you were going is what usually determines the extent of the damage.

While the RPMs are low, such as when you’re idling or moving slowly, only a small amount of water may enter. In this case, you need to act swiftly to remove it before it causes corrosion issues.

If you were going fast when the hydrolock occurred, where the RPMs were high, severe damage might occur.

Some of these include:

• A bent or broken connecting rod
• A breach in the head
• Crankcase damage
• A bent valve
• Damage in the bearings
• Piston ring damage
• Harm to the block

When associating the words “metal” and “water,” the first thing most of us think of is rust. This is precisely the case with hydrolock.

If you don’t act quickly to remove the water, your engine will rust, which will likely render it useless.

How To Fix A Hydrolocked Engine

Whether a fix is possible depends on the amount of water that has entered, as well as how long it’s been there.

If you were moving at a slow rate of speed when the RPMs were low, you might be able to clear the system of water by yourself.

This involves removing the spark plugs, starting the engine, and then revving it while it’s in park. You should notice water spewing out of one or more cylinders. You should also replace the spark plugs with new ones. Though, in an emergency situation, you should be able to just dry yours off.

It’s also important to wipe down the cylinder walls to remove moisture that might cause corrosion. Though, again, if you don’t have access to a safe space, you can always do this once you are.

The other possibility is that there’s a lot of water inside your engine. In this case, there’s really nothing you can do other than salvage what you can and replace the rest. In a worst-case scenario, a hydrolocked engine can cost anywhere between $3,000-$8,000.

It’s Probably Better To Go Around That Puddle – Not Through It

What’s the best course of action if you think you’ve hydrolocked your engine?

Don’t wait – because the longer you do, the better the chances you will end up with corrosion damage.

The worst case is that your engine is shot, and you need a new one. Don’t ignore this one. Your bank account will thank you later.

Last Updated on October 10, 2022

In a perfect world, every engine would run as intended for an indefinite period of time, free of significant issues. Unfortunately, mechanical devices of any type are prone to failure in time, with the internal combustion engine being no exception. Though unpleasant to think about, a vehicle’s engine can fail in several specific ways, leading to damage of varying degrees.

Of these conditions, few are as dreaded as hydrolock. Though generally rare, hydrolock can wreak havoc on an engine’s internal components, even damaging an engine beyond repair in the most severe cases. Luckily, most drivers will never encounter a true case of hydrolock. However, those that do will not soon forget it.

In any event, it certainly pays to understand the characteristics of hydrolock, as well as the root cause of this condition. Such knowledge has the potential to spare your engine from cataclysmic failure, preventing a series of hardships along the way.

Read on to learn more about hydrolock, as well as what to do, should you encounter this situation yourself.

What is a Hydrolocked Engine?

The term “hydrolocked”, describes an engine that’s internal movement is halted, due to the presence of fluid on top of one or more pistons.

Since fluid, in general, is largely incompressible, the piston found within the affected cylinder is prevented from reaching the top of its stroke. This effectively “locks” an engine’s rotating assembly in place, thereby preventing any further movement.

The most common culprit behind hydrolock is the inadvertent introduction of water into an engine’s cylinders. However, the escape of coolant into a cylinder, as the result of another mechanical issue, can also pose a risk of inducing a hydrolock condition.

Hydrolock can occur in engines that are both running and at rest, depending upon the exact situation at hand. In running engines, sudden hydrolock will lead to stalling, often at the expense of various internal components.

On the other hand, attempting to start a hydrolocked engine, that has previously gone unused, is generally a futile effort.

What Kind of Damage is Done When Hydrolocking?

When an engine hydrolocks, it is not uncommon for any number of internal components to become damaged. However, on rare occasions, an engine can also hydrolock without any discernible damage. 

By general rule, the amount of damage incurred from hydrolock is directly proportional to the speed of an engine when hydrolocking takes place. The faster an engine’s speed, the more devastating the results of hydrolock typically are.

Any damage observed when an engine hydrolocks, comes as the result of the sudden stoppage of mechanical components that had been operating at speed only moments earlier.

The momentum of an engine’s rotating assembly is often absorbed by the weakest associated component, as all comes to an abrupt stop. This is often enough to deform or destroy the individual component(s) in question.

The following are several of the most common kinds of damage observed during hydrolock.

• Bent or broken connecting rods
• Ejected piston/connecting rod
• Cracked cylinder head
• Cracked cylinder wall
• Damaged crankshaft
• Compromised bearings

Symptoms of a Hydrolocked Engine

The symptoms associated with hydrolock vary, based upon the exact operating conditions of an engine when such circumstances arise. However, a number of these symptoms are far more prevalent than others.

The following are several of the most common symptoms associated with engine hydrolocking.

Causes of a Hydrolocked Engine

#1 – Water

The most common cause of hydrolock is the intrusion of water from an outside source, into one or more of an engine’s cylinders. This situation often presents itself when a vehicle is exposed to flood waters of one degree or another.

When this occurs, water is allowed to enter through an engine’s intake manifold, before pooling within one or more individual cylinders. 

Some reports indicate that such issues are slightly more prominent in vehicles equipped with a cold air intake. This stems from the fact that cold air intakes feature an “open” air inlet, rather than an enclosed filter housing. Therefore, the introduction of even moderate amounts of water into the area surrounding a cold air intake has the potential to cause hydrolock.

Water intrusion of this type can occur in both running and non-running engines, though resulting damage tends to be far more severe when hydrolock occurs at full engine speed. In the event that an engine does hydrolock when in operation, no further attempts at starting should be made until all water has been manually expelled.

#2 – Coolant

Another common cause of hydrolock is the introduction of coolant into an engine’s cylinders, due to another form of mechanical failure. Issues of this nature are most prevalently associated with head gasket failure.

A failed head gasket often allows coolant from an engine’s water jackets to seep into one or more of an engine’s cylinders. Failure of this type presents the most significant risk when a moderate amount of coolant collects within a cylinder of a non-running engine.

Assuming that the affected cylinder does not fill to capacity, upward movement of the cylinder’s piston/connecting rod will still be possible until the intruding coolant reaches the bottom of the cylinder’s head. In many instances, enough momentum is gained prior to hydrolock, to cause significant internal engine damage. 

Can a Hydrolocked Motor Be Fixed?

Whether or not a hydrolocked engine can be fixed, is largely dependent upon a number of factors. These include the operational state of an engine when hydrolocking occurred, the number of cylinders that are affected, and the severity of damage incurred during hydrolock. 

In the case of severely damaged engines, such as those that have ejected a piston/connecting rod through the oil pan or block, the repair is highly unlikely. This is also often the case when a piston or connecting rod has distorted severely enough to cause significant damage to its corresponding cylinder wall.

On the other hand, engines that have simply “locked” due to the incompressibility of water, without incurring internal damage, can typically be restored to service. This is most often done by removing all spark plugs, before cranking an engine over. Water is purged through these spark plug holes, thereby remedying the hydrolock itself.

Additionally, one must also determine the source of the fluid intrusion, to prevent future episodes of hydrolock. This is fairly self explanatory in the case of a flood damaged vehicle. However, further diagnosis is required when the intrusion of coolant has led to a hydrolock condition.

In such cases, any mechanical issue leading to coolant intrusion should be remedied prior to returning a vehicle to service. This most often involves the replacement of an engine’s head gaskets. However, pressure testing should also be conducted to rule out the presence of a cracked engine block or cylinder head.