The Garage Maintenance & Repair

What Causes a Blown Head Gasket

It's not just something Subaru owners need to worry about

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Nearly everyone has heard the words “head gasket” at some point in their life, but nowhere near that many people actually know what one is or what it does. The head gasket is a seal that lives between the engine block and cylinder heads. It creates a seal to contain the internal combustion processes taking place and prevents coolant and oil from mixing in the engine.

When a head gasket starts to go bad, it can cause all sorts of other problems with the engine and exhaust systems. Any number of things can cause the head gasket to fail, from age to an overheated engine, to even a poorly installed gasket itself! No matter the cause, the problem requires immediate attentionATTENTION, THIS IS NOT A DRILL.

The Drive’s researchers and editors have been through the ringer with blown head gaskets before. We can tell you that taking your vehicle to a professional is the best way to get your head gasket issue diagnosed and either have a new one installed the right way or, well, learning you need a new car. Even so, we’re excited to share details on what causes head gasket failure and what you can do when you have problems with yours.

Let’s get started!

Your engine has a variety of gaskets.
Your engine has a variety of gaskets., Depositphotos

What Can Cause a Blown Head Gasket?


One of the best ways to prevent a catastrophic head gasket failure is to keep your car at the proper coolant levels. But even when properly filled and maintained, an overheating engine can occur and blow your head gasket!

Warped or Cracked Block or Head

An engine that has overheated can warp or crack due to the way heat distorts and changes metals. This can change the way the head gasket seals, which can lead to leaks.


Over time, the head gasket’s seals can break down and not do their job as well to prevent leaking and other problems. It’s best to learn when the manufacturer prescribes it be replaced and do so either before or right when you hit that mileage.

Improper Installation

If the head gasket or coolant system has been installed or repaired improperly, leaks and problems with engine temperature can become big issues.

What Are The Symptoms Of A Blown Head Gasket? 

Oil or Coolant Leaking

If you notice coolant or oil leaking on or around your engine head and block, it could be an indication that your head gasket is no longer sealed. 


If a head gasket blows, even slightly, the engine might not be able to cool itself down to acceptable driving levels. Overheating could damage several components within your engine, so immediately turn your vehicle off until you can determine the source of the issue. One thing you should never do when your car is overheating: Remove the radiator cap and check the coolant. That’s how you get a one-way ticket to the ER for a scalded face.

Engine Misfiring

For an engine to work correctly, spark, air, and fuel have to consistently work together with the precision of a Japanese sand artist. It has to be the exact amount of air mixed with the exact amount of fuel ignited with a specific spark voltage at a specific time. If any of these factors are off by a theoretical grain of sand, you could get preignition, knock, or misfiring. More than one of these factors could be affected by a blown head gasket.

Water Vapor or White Smoke Coming From Exhaust

If your head gasket is bad, coolant might work its way into the engine. If this happens, you could see white smoke or water vapor coming out of your exhaust pipe as a result.

Milky Oil

If you notice tan or milky colors in your oil, you might have a blown gasket—the underside of your car’s oil reservoir cap will likely become splattered with the milky oil. This happens when coolant comes in contact with and contaminates the oil. 

Bubbling Inside Radiator 

If you notice bubbling inside the radiator or coolant reservoir, it’s an indication your system has air in it, which could be caused by a leaking or blown head gasket.

Fouled or Wet Spark Plugs

If the gasket is blown, it’s possible for coolant, oil, or gas to get into the cylinders. This could foul or flood the spark plugs.

This is not a service you can ignore.
This is not a service you can ignore., Depositphotos

Pro Tips To Fix A Blown Head Gasket

Like the Wu-Tang Clan, blown head gaskets ain’t nothin’ to mess with. The Drive’s researchers have come up with a few tips to help you avoid catastrophic engine failure.

  • Unless you’re an experienced home mechanic, you’ll want to flat-tow the car to a shop. 
  • Some of the symptoms of a blown head gasket are similar to the symptoms of other engine problems. That can make it hard to identify the problem, but a good rule of thumb is to get the car to a mechanic as soon as possible.
  • Products like head gasket sealer can help you limp the car to a mechanic, but don’t treat them like a fix. 

Get Help With Blown Head Gaskets From a Mechanic On JustAnswer

The Drive recognizes that while our guides are detailed and easily followed, a rusty bolt, an engine component not in the correct position, or oil leaking everywhere can derail a project. That’s why we’ve partnered with JustAnswer, which connects you to certified mechanics around the globe, to get you through even the toughest jobs. 

So if you have a question or are stuck, click here and talk to a mechanic near you.

FAQs About Head Gaskets and Head Gasket Repair

You’ve got questions, The Drive has answers!

Q. Can You Fix A Head Gasket Yourself?

A. Yes and no. Yes, you can try, but it’s unlikely you’ll succeed unless your garage resembles that of Jay Leno’s. 

Q. Why? How Hard Is A Head Gasket Repair?

A. Well, even though a new head gasket is relatively inexpensive, it’ll take even a DIY Garage Hero a few hours JUST to disassemble the engine and actually get access to the head gasket itself. Then, you’ll likely have to fix the problem that caused the gasket to fail, which if it’s a cracked or warped block, you aren’t going to fix at home. And even if you get that far, there’s the job of recreating the seal that was present in the engine when it rolled off the assembly line. That’s a tall order to fill.

Q. Can You Drive A Car With A Blown Head Gasket?

A. No, you can’t. A blown head gasket can cause all sorts of other problems. Coolant can enter the cylinders, which can cause major damage quickly. It can also allow coolant to leak from the engine, causing overheating. 

Q. Does A Blown Head Gasket Ruin An Engine? 

A. If you catch the problem early enough and actually take care of it instead of ignoring it, there’s a good chance that the engine can be repaired. The good news is that the symptoms of a blown head gasket are easy to identify. Head to a mechanic as soon as possible to get it fixed.

Q. How Much Does It Cost to Fix a Blown Head Gasket?

A. Repairing a blown head gasket is a serious business. Between the cost of parts and the labor time, you’ll be looking at a repair bill that can land upwards of $2,000 in some cases. Prices climb to the top end of that estimated range when there are additional issues that need repairs. In some cases, replacing a blown head gasket can feel like it costs more than the car is worth, but unless you’re planning on selling or scrapping the car you don’t have many other options to get it back on the road.

Q. Do Head Gasket Sealers Actually Work?

A. Opinions are split on how well quick fixes like head gasket sealers actually work. On one hand, they can provide a temporary solution to get you and your vehicle to the next service station. On the other hand, head gasket sealants can remain in your vehicle’s coolant system for quite some time and may require extra effort to drain and clean the system afterward.

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Chris Teague


After working in the technology and software industry for several years, Chris Teague began writing as a way to help people outside of that world understand the sometimes very technical work that goes on behind the scenes. With a lifelong love of all things automotive, he turned his attention to writing new vehicle reviews, detailing industry trends, and breaking news. Along the way, he earned an MBA with a focus on data analysis that has helped him gain a strong understanding of why the auto industry’s biggest companies make the decisions they do.