What are the Symptoms of a Blown Head Gasket?

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Failed cylinder-head gaskets send many cars to the classifieds as “mechanic’s specials” or even to the scrap yard. When a head gasket blows, many owners think it’s more trouble than it’s worth to repair and instead decide to rid themselves of the burden.

Is it that big of a deal? Could be. The thing about a cylinder-head gasket is that it serves a few purposes. If it’s blown, it might be linked to another, more serious issue or have caused a lot more damage.

Car Bibles is here to help. We’re going to talk about cylinder-head gaskets so that you know what to look for and how to handle the situation.

Ed. Note: This post was updated with all-new text and photos on 8/19/2023.

What Is a Head Gasket?

Although engines are produced with masterful engineering and carefully manufactured components, there will always be imperfections along the many mating surfaces of parts.Those imperfections might be deviations of only a couple thousandths of an inch, invisible to the naked eye. But those uneven mating surfaces create passages through which fluids and air pressure can leak. Gaskets, which can be made from a variety of materials such as fabric, rubber, or paper, are used to fill the gaps between those surfaces and help to better seal each component to each other.

A cylinder-head gasket is what comes between the engine block and the cylinder head. Its job is to aid in containing the many pressures in the engine cycle as well as the flow of fluids that travel between the block and the head. Things like oil and coolant need to stay in their respective passageways in order to keep the engine running efficiently.

As shown here, the gasket lives between the head and the block. Photo: Hank O’Hop
As shown here, the gasket lives between the head and the block. Photo: Hank O’Hop

Why Do Head Gaskets Fail?

The head gasket is trapped between two fastened components that work together to create tremendous forces and heat. Even on a good day, the head gasket is responsible for containing a rather violent cycle, but it’s still expected to last about 200,000 miles or so under normal circumstances. So, why do they fail?

Over time, fluctuating temperatures, vibrations, and general wear and tear can take quite a toll on the gasket. If there are any imperfections in the gasket or castings that the gasket can’t accommodate, it may fail prematurely. Improper installation will also shorten the life of the gasket.

The most likely cause for the gasket to fail is excessive heat. As things go through heat cycles, they will expand or contract. If the heat becomes too great, the tolerances between the head and block might change from what the gasket can handle. This leads to its inevitable failure.

What Are the Symptoms of a Blown Head Gasket?

Specialty equipment can go a long way when diagnosing a blown head gasket. Leak-down testers and compression testers can help you to determine quite a bit about the engine’s condition. If you use the tools properly, you can even find if the problems you’re experiencing are because of another issue altogether.

As great as that is, not everyone has access to these tools. We also know that the cost of repairs might not leave room in the budget for some fancy equipment. So, let’s talk about some of the obvious signs of a blown head gasket.

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Here are some of the top symptoms of a blown head gasket. Keep in mind that they can be linked to other issues, however, so you won’t know that the gasket is the problem for sure until you tear the engine down or perform additional tests.

Milky oil

The block and head have passages for water to flow through. They also have large openings for the cylinders and tiny passages for oil or water to pass through on many engines. If the gasket is compromised and fails to keep a seal between these passages, water may leak into the cylinders or the oil-feed holes. If this happens, your oil may become polluted with water.

When water and oil mix, a milky-brown color is created. If the oil is that color when you pull the dipstick or drain it, there is a good chance the head gasket has failed.

Overheating/bubbling radiator

A failed head gasket can create a leak in the cooling system. If it does, you may very well experience some overheating. Keep in mind that the leak doesn’t just need to let water out. The pressures and heat from the combustion chamber may pollute the cooling system, causing the fluid to bubble. The combination of these two issues can be linked together to pinpoint an issue with the head or its gasket.

Lack of power

Engine power is highly dependent on the pressures created during the combustion cycle. Any leaks will reduce pressure, therefore impacting power. Not only that, but water and oil entering the system will also take a toll on the fuel and air mixture and could reduce efficiency. In other words, a blown head gasket can leave your car feeling rather sluggish.

Washed spark plugs/oil deposits

Learning to read spark plugs is one of the best ways to monitor the running condition of your engine. What’s on the plug tells you if the engine is running too rich or lean or if the plugs are due for a change. The plugs can even tell you if there is oil in the cylinders, which can be linked to a head-gasket issue.

What if there’s nothing on the plug? Well, something’s been cleaning it up. Could be water that’s making its way into the cylinder because of a faulty head gasket.

White smoke from exhaust

Another troubleshooting trick you want to learn is how to read exhaust smoke, because its color can tell a lot about the engine’s condition. For example, when water and coolant from your radiator burns in the combustion chamber, white smoke is produced. It may be entering the chamber on account of a damaged head gasket.

On the left, there is no gasket, while the right photo shows a new gasket

Does a Blown Head Gasket Mean My Engine Is Dead in the Water?

People treat the phrase “blown head gasket” as a dirty word because of the implications. Often, a blown head gasket means other parts of the engine were already damaged, or the failed gasket led to severely damaged engine parts. That’s not always the case, but either way the job requires opening the engine up to inspect it yourself and assess the situation. How difficult can that be? We explain below.

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Is Fixing a Head Gasket Easy?

Theoretically, it could be, but don’t count on it. Replacing a cylinder-head gasket might be a simple nuts and bolts job where the level of difficulty is based more on the steps required to tear down your particular engine. You just might get lucky and have the old gasket to blame for all of your problems. That’s unlikely, however, and you never want to go into the repair assuming that’s the case.

There might be another, more serious issue that caused the gasket to blow in the first place. For example, the actual head might have warped after thousands of heating and cooling cycles. If it has, you’ll either need to have it resurfaced or replaced. Check the surface of the heads or have them checked because if you miss a warped head, the new gasket will fail in short order, and you’ll be back at square one.

There is also the chance that the engine is overheating on account of a faulty cooling system. Look over your radiator, water pump, thermostat, and all of your other cooling components to be safe.

A leaky cylinder head also might allow coolant to pollute your oil supply. You might not have much to worry about if you act fast, but if you let the issue go for too long, you just might end up needing to replace the bearings in your bottom end or send the entire engine into the machine shop for repairs.

In short, replacing a cylinder-head gasket warrants inspecting multiple systems and components along the way because the issues are typically not isolated to the gasket. If you don’t, you can miss a major detail that will necessitate tearing the engine down again or dealing with catastrophic failure. It might be extra work now, but it can save you from some major headaches later on.

After you remove the old gasket, you need to scrape the surface clean to prepare for a new gasket

Points of Failure With Similar Symptoms

A blown head gasket shares symptoms with some other issues. You might think the white smoke coming from the exhaust or milky oil is on account of a blown head gasket when in reality, something else has gone wrong. Perhaps the most concerning issue with similar symptoms is a cracked cylinder head. It’s more likely that the gasket blew, but you don’t want to take chances. This problem won’t just go away after throwing a new gasket in place.

Oil deposits on spark plugs can be on account of a blown head gasket as well, and it is something to keep an eye on. However, this issue is more likely linked to faulty valve-stem seals. A head gasket is far more likely to fail between the openings for the combustion chambers and water jackets. If you have the proper diagnostic tools on hand to check the valve-stem seal, you might even be able to perform a repair without removing the head.

Oil on the plugs can also be linked to an issue with the piston rings, since bad rings will let oil up from the crankcase, or possibly even a cracked cylinder head. In either case, a head gasket is the least of your worries.

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You don’t want to treat a head-gasket replacement as a simple job. If you tackle this on your own, make sure to take your time and know that you might need to ask for help from a professional. Ensure it is, in fact, a blown head gasket that you’re dealing with by inspecting everything along the way.

Car Bibles Glossary for Head Gaskets


A component used to create a seal between mating surfaces. The purpose of this component is to fill in any minor imperfections on these surfaces that would otherwise create gaps. A gasket is typically made of fabric, rubber, paper, cork, metal, or fiberglass.

Cylinder head

The top half of an engine housing your valvetrain components, spark plugs, and the compression chamber for the cylinders. The cylinder head also links to the induction and exhaust systems as it controls airflow to and from the combustion chambers.

Engine block

The lower half of the engine containing the combustion chamber, rotating assembly, and many other components. This is often viewed as the main component of the engine as it houses some of the most crucial parts.

A gasket creates a buffer and seal between two mating surfaces
A gasket creates a buffer and seal between two mating surfaces

FAQs on Blown Head Gaskets

You have questions, and Car Bibles has the answers.

Q: Can you still drive a car with a blown head gasket?

A: The car will probably run with a blown head gasket, but you definitely don’t want to keep driving it. If you’re letting water into the crankcase, are continuously overheating, or even running with a misfire, you’ll likely cause a lot more damage to your engine.

Q: What does a blown head gasket sound like?

A: A bad head gasket can allow compression to escape, and that might sound a lot like an exhaust leak. It can also cause misfiring, in which case the engine will run rough. These symptoms can be linked to other problems, so make sure to diagnose the appropriate areas before assuming you have a blown head gasket.

Q: Is it worth fixing a blown head gasket?

A: A blown head gasket isn’t necessarily an immediate death sentence to your vehicle, and you likely can fix the problem. However, the repair costs can be pretty high, and additional damage can beat the snot out of your wallet. Whether or not it’s worth fixing is dependent on what you’re willing to spend on your car.

Q: How do you fix a blown head gasket without replacing it?

A: You can’t. Some elixirs claim to work miracles, but take the time to repair the issue the right way. Those magic chemicals might get you by for a few miles, but they only mask the problem and don’t fix them.

Q: Can you fix a blown head gasket by yourself?

A: You can replace the gasket by yourself. You may even be able to perform some other repairs as long as you have the right equipment. Unless you have access to a machine shop, however, you will need a professional’s help with resurfacing and inspecting the heads for microscopic cracks.

Originally posted 2023-11-28 15:26:55.

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