What are the Signs of a Blown Head Gasket?

The head gasket, which is located between the engine block and cylinder head, seals the combustion chambers to prevent compression loss. It also plays a role in sealing the coolant and oil passages running between the engine block and head.

Head gasket failure is almost always the result of engine overheating⁠—but there are some instances where a head gasket can deteriorate over time, or fail as the result of a manufacturing defect. Fortunately, there are signs of a blown head gasket that will warn you about any issues with the seal.

Is your head gasket in bad shape? Read on to find out what signs you should look out for.

7 Blown Head Gasket Symptoms

If you’re running with a blown head gasket, chances are you’ll experience one or more of these symptoms:

Continuously Depleting Coolant

In the middle of the head gasket, there are large-diameter openings for the engine’s combustion chambers. Also, because there are oil and coolant passages running between the engine block and cylinder head, there are openings to accommodate for these passages.

If the head gasket fails, the coolant passages and combustion chambers may no longer be separated from one another. As a result, the coolant can enter the combustion chambers, where it is burned during engine operation.

Thick White Exhaust Smoke

As was mentioned above, a blown head gasket can allow the coolant to be burned inside the engine. When this happens, the coolant often turns to white steam emanating from the car’s exhaust. The steam has a sweet smell and is often mistaken for smoke.

Although not nearly as common, it’s also possible for a blown head gasket to allow oil to enter the combustion chamber, resulting in gray-white or gray-blue smoke.

Higher Engine Temperature

An engine will overheat if there’s not enough coolant in the cooling system⁠—and a blown head gasket can result in a low coolant level. So, as you might guess, a bad head gasket can lead to overheating, which often results in significant engine damage.

Bubbles in the Radiator and/or Reservoir Overflow

A blown head gasket can allow combustion gases to enter the cooling system. Because of this, there may be visible bubbles in the radiator and/or coolant reservoir.

You may also notice that the cooling system is under extreme pressure.

Oil-Coolant Intermix

Remember how we mentioned the head gasket has openings for the engine’s oil and coolant passages? Well, if there’s a breach between those openings, you might end up with oil in the coolant or visa versa.

Sometimes this results in a foamy substance under the oil fill cap or on the oil dipstick.

Compression Loss/Engine Misfire

An engine needs three primary ingredients to run properly: a precise air/fuel mixture, adequate spark, and the right amount of compression. A disruption anywhere in that formula can result in incomplete combustion and an engine misfire.

And if you’ll recall, the head gasket prevents a loss of compression by sealing the combustion chambers. Therefore, a blown head gasket can result in a loss of compression and an engine misfire.

External Fluid Leaks

In some instances, the oil and coolant passages can breach at the outer perimeter of the head gasket. When that happens, you’ll have an external coolant and/or oil leak coming from the engine.

What Causes a Blown Head Gasket?

Now that you know the common signs of a blown head gasket, it’s time to learn about the possible reasons behind its failure. This knowledge will help you identify what caused the problem and determine how to fix it.

The head gasket may expand if the engine’s operating temperature exceeds the normal temperature range for its specification.

If the temperature becomes too hot, the cylinder head and other metal parts in the engine including the engine block will expand, stretching, or tearing the head gasket, which will be the cause of a leak.

Can You Drive with a Blown Head Gasket?

The short answer is no. A blown head gasket can cause damage to other parts of your vehicle, such as the engine, cooling system, and catalytic converter.

What you can do if you find your car still driveable is to bring it straight to the mechanic. If the problem gets worse before you are able to do this, have a tow truck bring it to the nearest service center.

Whatever happens, if you suspect a blown head gasket (which you should be able to detect once you observe any of the aforementioned symptoms), do not ignore it as it may lead to an even bigger headache. Thus, it’s recommended to familiarize yourself with the signs of a blown head gasket.