Understanding the Telltale Signs of a Blown Head Gasket

Understanding the Telltale Signs of a Blown Head Gasket

February 21, 2024 0 By CarGuy

A blown head gasket can mean the hell broke loose in your engine, if this problem is left unaddressed, it can result in some really costly repairs. So, understanding the signs of a blown head gasket is really important.

For those who don’t know what a head gasket is, this is a component made from multi-layered steel. This piece is mounted between the engine block and the cylinder head.

The head gasket has only one role, which is keeping a good seal in the engine and preventing oil and coolant to leak or come into contact with one another and mix.

This is something you don’t want to happen. Since it can be very pricey to get the problem fixed. But this is why we are here to help you out.

Signs Of a Blown Head Gasket

Now let’s elaborate on all of the signs of a blown head gasket and learn more about what can you expect if a head gasket is blown inside your engine.

We will elaborate everything in great detail, so you get a really good perspective of what to expect.

1. Overheating Engine

One of the telltale signs of a blown head gasket is the overheating engine. If the gasket fails, the engine will tend to overheat.

Usually, the gasket fails precisely because of overheating and the overheating continues after the gasket has failed.

Having a blown head gasket will allow fluids to move in places where they shouldn’t and also cause compression loss in some cases.

The cooling process is disrupted and the temperatures will rise. The needle will slowly creep into the red zone and the engine will not be happy at all.

The performance will be very poor and you will eventually have to stop until the engine cools off in order to resume driving.

An important note is to never open the cap of the radiator or the expansion tank when the engine is warm. You could seriously burn yourself in the process because the coolant is boiling hot.

2. White Smoke from the Exhaust

White smoke from the exhaust is another telltale sign of a blown head gasket. So, why is this the case?

Well, white smoke usually appears if the engine consumes coolant. Coolant is leaking into the combustion chamber.

Then this fluid is ignited with the air and fuel mixture and white smoke is produced.

So, if you notice that the exhaust produces white smoke and there is a sweet odor, this is a strong indication that the head gasket has failed and needs to be replaced.

3. Milky Oil

Another common sign of a blown head gasket is a milky engine oil. Milky engine oil is basically oil that is mixed with coolant.

Many people think that if they notice such a thing on the oil cap the head gasket is bad. Which is not the case in many situations.

In order to be sure, pull out the dipstick and if the dipstick is covered in milky residue, then you have a blown head gasket.

If the oil on the dipstick is clean, you should not worry. The milky residue on the oil cap is only condensation.

4. Loss of Coolant without Visible Leaks

If the engine starts losing coolant without any visible leaks, then you might have a coolant leak or a blown head gasket.

This is why in this case, we advise inspecting the cooling system and if there are white stains on the coolant hoses, this could mean that there is a leak.

And if the hoses are good and there is no visible leak anywhere, the head gasket is probably blown and the car is burning the coolant.

Sometimes these coolant leaks can also be external and coolant can leak from the sides of the block.

This is also often accompanied by white stains. So, a thorough visual inspection is needed in order for you to determine where the coolant is going.

5. Engine Misfires or Loss of Power

A blown head gasket can also disrupt the combustion process and cause misfires and power loss.

This is the case because whenever you have a blown head gasket, you basically have a compression leak.

Your engine has a hole and this is causing the engine to lose compression. No compression means no power.

So, if you experience engine hesitation, rough idle, and poor performance. This can mean one thing, that the engine has a problem and this needs to be addressed as soon as possible.

If not, you risk potential permanent damage to the engine in the process. So, that’s why you shouldn’t ignore this problem.

6. Pressurized Coolant System

The cooling system of the engine will also be too pressurized in some cases. Which is another telltale sign of a blown head gasket.

This is often the case because of a compression leak. There will be air that will go into the cooling system.

This will create bubbles in the coolant expansion tank and overpressurize the system.

If the expansion tank has a bad valve and is not releasing the pressure, the tank could simply explode.

So, if you notice such a thing, you should definitely address the blown head gasket.

7. External Coolant Leaks

External coolant leaks are another clear sign that you have a blown head gasket.

Coolant can also leak from the external side of the engine block. Whenever you have such leaks, there could be evaporation and a sweet smell.

Also, there will be white stainage around the head gasket where the leaks come from.

This is the case because coolant quickly evaporates when in contact with the hot engine block.

How To Fix The Blown Head Gasket?

Fixing this problem is not a simple thing. For this purpose, you need to visit a shop.

This is the case because the cylinder head has to be resurfaced. In 99% of the cases, the cylinder head is bent because the engine was overheating.

So, the cylinder head has to be perfectly straight in order for the new gasket to be placed in and then bolted onto the block.

All this is somewhat expensive but it has to be done in order for the engine to run smoothly once again.


Recognizing the signs of a blown head gasket is really important if you want to preserve the engine.

If you delay the replacement, the engine could become irreparable and you will need a new engine in the process.

So, if your engine has milky oil, bubbles in the expansion tank, coolant loss, and white smoke from the exhaust, this means that you have a blown head gasket.

That’s why you should be proactive and find a solution to this problem as quickly as possible and avoid paying thousands of dollars in the long run.


What are the signs of a blown head gasket?

Signs of a blown head gasket include: milky engine oil, loss of coolant, overheating engine, white smoke from the exhaust, bubbles in the expansion tank, and external leaks.

How much it costs to fix a blown head gasket?

The cost to fix the problem really depends on the sitaution. But in general, about $1,000 in the best case scenario. Sometimes it can cost a lot more if you need a new cylinder head.

If you want to read more about head gaskets, you can check our article on the 7 main symptoms of a blown head gasket.