
When an engine is seized from ingesting a substantial amount of liquid; it is said to be a hydrolocked engine.
So, with all internal combustion engines, the internals are all designed to deal with the compression of air.
Because, liquid is non-compressible, when ingested into the cylinders, it is said to be hydrolocked.
So, the amount of damage from a hydrolocked engine, depends on the engines speed when the liquid was ingested.
Also, the amount, type of liquid and how it got in, will have a major effect on what happens. So, when your engine first encounters a bit of extra liquid in the cylinders; your engine will begin to misfire. However, if it’s just a small amount of liquid, it might just blow it right out the exhaust. But, if more liquid is drawn in, you’ll hear a loud knocking noise as the cylinders fill up.
So, it could be just a second or two and then your engine will shut off with a thud.
Causes Of A Hydrolocked Engine
By and large, the most common cause of a hydrolocked engine is, water entering the air intake. Water can enter the intake on any engine, whether it’s from driving through water or an actual flood.

Also, engine coolant can enter the cylinders when a head gasket blows. A failure in the carburetor or injectors can introduce, liquid gasoline or diesel into the cylinders.
Damage From A Hydrolocked Engine
Big leak, fast engine speed
The real damage occurs when a large volume of liquid makes its way into the cylinders.
Also, with higher engine speed comes more engine damage. ( Almost sounds like a quote from Spiderman )

The reaction forces involved will almost certainly, break internal components like:
- Piston Damage
- Cylinder Walls Crack
- Connecting Rods Bend
- Connecting Rods Snap & Go through the oil pan
- Damage to the cooling system
- Cold Water Shock to Hot Engine
- Head Gasket Failure
- Catalytic Converter Damage
- Rod/Main Bearing Wash out
- Crankshaft Damage
Again, the amount of liquid ingested and where it came from, will reflect the amount of damage.
Small leak, slow engine speed

The hydrolocked engine was a symptom, not the cause. So, if the liquid was introduced to the cylinder through a failed component; typically the head gasket, this must be repaired.

So, coolant is corrosive to the internal parts of an engine. As a result, when you leave this standing for any length of time, the damage will only get worse. Also, remember engine coolant eats bearing material.
- Starter
- Flywheel
- Transmission
- Cause A Head Gasket Leak
- Engine Block
- Transmission Housing
- Connecting Rods
- Pistons
Consequently, a hydrolocked engine, can also occur when the engine is not running. Flood damage, for example. Fluid fills the cylinders while the engine is not running and the starter can’t crank the engine over.

Conclusion
So, the best thing to do is, avoid drive through any flooded streets. But, if you do, slow down.
So, the most disconcerting aspect of a hydrolocked engine is, that it can strike without warning. That’s why regular maintenance and inspections are the best way to keep on top of this issue. Preventative maintenance is a lot cheaper and much safer, than a hydrolocked engine.
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