What Does It Mean to Hydrolock Your Motor?

You’ve been told that driving through puddles is a bad idea. In theory, you understand that many of a car’s systems don’t work well when water is introduced to the equation. Your car is susceptible to:

• Premature corrosion

• Electrical shorts

• Contaminated fluids

• Water entering the engine

But, when the situation presents itself, you might not always consider the ramifications. You see water in an underpass, but don’t realize it’s four feet deep. You’re splashing your truck through a creek when the hood dips below the surface. Hurricane floodwaters quickly rise as you’re making a mad dash to high ground, and you’re cornered.

Immediate Signs of a Hydrolocked Motor

What happens next is sickening, the hydrolocked engine sound. You might hear a slight sputter, then your engine comes to a jarring halt. When you try to restart the engine, there’s not even a tiny chance it’s going to turn over. Your engine is hydrolocked.

What is Hydrolock?

The technical name for it is hydrostatic lock. The term has been shortened to hydrolock, but the meaning is the same. Simply stated, it means a fluid is preventing the pistons from reaching the top of their stroke. For an engine to become hydrolocked requires fluid to enter one or more cylinders, and the fluid needs to be more volume than the combustion chamber allows when the piston is at its uppermost travel in the compression stroke. In other words your engine has locked up. 

Normally, the piston compresses an air/fuel vapor mixture in the cylinder. Fluid simply doesn’t compress like a gas does. When the piston reaches the fluid, it comes to an abrupt halt. And, when one piston stops, they all do. Your engine shuts down, and you’re left wading through water to get to safety.

What Damage is Done in a Hydrolocked Motor?

If you’re driving your car when a water hydrolock occurs, the extent of the damage usually depends on your engine speed.

• If your engine is at low RPMs, such as an idle, when water gets into your engine cylinders, you may escape with no damage at all. That is, aside from a stalled engine, a tow to a shop, and an immediate hydrolock engine repair. If quick action isn’t taken, the inner engine parts can corrode and pit, rendering them completely garbage.

• If your engine is running above an idle, like driving down the road, an engine hydrolock will have dire and extensive consequences. The force behind the pistons moving upward can bend the connecting rod, crack the crankshaft, cause fractures in the cylinder walls, blow oil seals in the cylinder head, and more. If the engine is running at full tilt, a connecting rod can break and bash right through the engine block.

Hydrolocking can also occur when the engine is not running. It’s the case with flood cars, for example. Fluid fills the cylinders while the engine is not running and the starter can’t crank the engine over. The only damage you’re likely to encounter in this scenario is in the event the fluid isn’t removed quickly, and the engine’s insides corrode.

Hydrolocked Engine Symptoms

Will a hydrolocked engine turnover? Well, when your engine first encounters a bit of extra liquid in the cylinders, a dead miss will happen. Your engine will run noticeably rough. If it’s just a bit of water, it might blow right through the exhaust, but if more water is drawn in, you’ll hear a loud knocking noise as the cylinder fills up. It could be just a second or two, and then your engine will shut off with a thud. At this point your engine will not turnover and you're stuck. So what are the causes and hydrolocked engine symptoms?

Causes of a Hydrolocked Engine

By and large, the most common cause of hydrolock engines is water entering the air intake. More specifically, a cold air intake system that is immersed in water is the typical cause. Air can enter the intake on any engine though, whether it’s from driving through water deeper than the intake or submerging a running engine’s air intake in water.

Flooding isn’t the only potential cause. Engine water, known as coolant, or oil from a badly leaking head gasket can fill a cylinder beyond the combustion chamber capacity. The consequences are virtually the same, except engine oil won’t corrode like water does.

In a small sampling, fuel is one of the liquids engine hydrolock can be caused by. If a carburetor jet is stuck or a fuel injector is leaking, more fuel can dump into the combustion chamber than the engine can burn. It’s more common in diesels, because the high pressure fuel injection pump can send immense amounts of fuel directly into the cylinder.

Regardless of the cause, the symptoms remain the same.

The Effects of a Hydrolocked Diesel Engine

Hydrolocking can happen much more easily on diesels. The engines are higher compression because the combustion chambers must be lower volume. That means a smaller amount of engine water is needed to cause the effects. And, because diesels are known for their torque, the potential for catastrophic engine damage is even greater than a gas engine.

How Do You Fix a Hydrolocked Engine?

It’s relatively easy to hydrolock car engines, but it’s not that simple to fix them, since water entering internal components in a combustion engine causes much unseen damage.

• First, the water must be removed from the cylinders. The spark plugs are removed and the engine is cranked over. In engines that were hydrolocked at idle or when the engine was not running, it may be all that’s required to clear the obstructing water, so removing the spark plugs isn't necessary. Cylinder walls won’t be corroded if the water is cleaned out soon after the occurrence. A new set of spark plugs, an oil change, and the car could potentially be running again.
• If the engine was well above idle when water entered the engine, you’re almost guaranteed to have damaged internal components. The internal combustion engine needs to be pulled out, stripped down, and every part inspected for damage. You’ll usually find bent connecting rods, scored bearings, and even cracked pistons. The cylinder head should be pressure tested, and the engine block checked for cracks. The crankshaft should also be measured to make sure it’s not bent.

Hydrolocked Engine Repair Costs 

Often, the least involved corrective action is an engine replacement for your car to start as normal. Whether a new or used engine is installed, your hydrolocked engine repair cost is going to be in the thousands of dollars. Typically, you can expect a labor-intensive hydrolocked engine fix to run anywhere from $3,000 to $8,000.

If you don’t want the headache of dealing with your hydrolocked engine, you have an option. CarBrain can get you out of your broken-down car without needing to fix the engine first. Just click the button below to get a guaranteed offer for your car in ‘as-is’ condition. Once you accept our offer, we’ll send a truck to collect your car, blown engine and all, and put a check in your hand.

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