How to Identify and Fix a Head Gasket Leak

Head Gasket issues are not trivial. To put it simply, a head gasket leak can cause significant issues with a vehicle’s engine if left unchecked over time. One of the most critical effects of a leaking head gasket is that it can result in a gasket oil leak. This is not an ideal situation, and vehicle owners and drivers should be savvy toward detecting and correcting a head gasket leak before it turns into a blown head gasket, or worse.

In this article, we will explain what a head gasket leak is, how it differs from a blown head gasket, how to identify a leaky gasket, and what you can do about it. AutoZone carries a variety of head gasket sealants starting from just $15. This is much more cost effective, considering that a typical head gasket repair can cost upwards of $2,000 at a shop, not including the cost of vehicle downtime and required alternative commuting arrangements.

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What is a Head Gasket Leak?

A head gasket leak is when liquids and gases from the engine block leak into places where they are not meant to go. An engine block has a myriad of channels that carry coolant, engine oil, and the cylinders themselves which contain the fuel and air mixture. Typically, you do not want oil or coolant to leak into the cylinders, and the head gasket helps maintain separation.

However, head gaskets can deteriorate over time, as they are exposed to extremes of temperature and pressure, as well as natural aging and breaking down. This can result in a head gasket leak that, if unchecked, will result in total failure of the head gasket and extensive damage to the vehicle’s engine, necessitating expensive repairs and significant downtime of the vehicle.

What’s the difference between a Blown Head Gasket and a Leaking Head Gasket?

A leaking head gasket will definitely lead to a blown head gasket if unchecked. Typically, head gaskets do not blow in one go unless subjected to unusual operating and loading conditions such as excessive turbocharging or supercharging from aftermarket tuning, or a manufacturing defect in the head gasket.

A vehicle can be driven for some time on a leaky head gasket, however this is not possible with a blown head gasket, as the vehicle’s engine may be unable to generate significant compression, and extensively leak oil and coolant. Attempting to drive a vehicle with a blown head gasket will cause significant damage to the stressed engine, and it may overheat and seize up, or the engine block could be damaged by the pistons attempting to compress incompressible liquids such as coolant.

As well, a leaky head gasket can be repaired with head gasket repair products that will instill it with extra life, and these products can be administered by an owner or driver. In contrast, a blown head gasket cannot be repaired, and the only avenue to fix it is total replacement of the head gasket, which requires a visit to the workshop and can cost hundreds of dollars in parts and labor.

Signs of a Leaking Head Gasket

There are several signs of a bad head gasket. While a leaking head gasket itself may not result in an error code and Check Engine Light (CEL) illumination, there are telltale signs that a savvy owner or driver can identify, and these are some of the leaky head gasket symptoms.

  • Is the vehicle consuming more engine oil than usual? If you are finding that your vehicle is consuming oil between oil changes, there is a leak somewhere, and it could be in the head gasket. Even if there is no visible oil leak, an oil gasket leak can cause oil to leak into the cylinders and combust.

  • Typical automotive exhaust is colorless, while symptoms of leaking head gasket will enable coolant or oil to enter the cylinders and combust, with a resulting color tinge in the exhaust emissions. If smoke from the tailpipe is white, it signifies a coolant leak, while if it has a bluish tinge, the culprit is engine oil that is combusting.

  • Is the engine overheating? A leaky head gasket can cause coolant to leak out, reducing coolant pressure in the cooling system and decreasing effectiveness. Signs of a bad head gasket can also be observed as a reduced coolant level in the overflow bottle.

  • Is there an observed leak of oil or coolant on the engine’s head? Modern cars have engine covers to present a more aesthetically pleasing view when the hood is opened, but these can easily be removed to expose the engine and drivetrain, and a visual check performed.

  • Is the engine running rough or hesitating, and are the spark plugs fouled with oil? If they are, it is a typical sign of a leaky head gasket.

  • Observe the condition of engine oil when performing an oil change. If the oil appears milky or tinged with the color of coolant, there is a head gasket leak that is allowing oil and coolant to mix.

How to Repair a Head Gasket Leak

Repairing a head gasket leak can be surprisingly easy, as AutoZone carries products for this purpose, which are called Head Gasket Sealants. Using a head gasket sealant can be performed by a competent owner or driver who is mechanically knowledgeable, however one should first establish that any symptoms as described in the previous section are caused by a leaky head gasket, and not by a cooling system leak, for example. AutoZone has a comprehensive guide on how to use a head gasket sealant. Head gasket sealants are typically administered via the cooling system, which must first be flushed out to eliminate debris. Once a radiator and cooling system flush is performed, the radiator is filled with water and an appropriate amount of sealant is added, determined based on the cylinder count of the engine. The engine must be adequately warmed up as well to ensure maximum performance of the sealant. Proper utilization of head gasket sealant can extend the life of a head gasket for many more thousands of miles.

The alternative repair is a head gasket replacement. Typically, that involves around 10 hours of labor – perhaps more if you do it yourself – and hundreds of dollars in parts. The top end of the engine is removed, the surfaces cleaned and prepped, and the new gasket installed before reassembly. The average head gasket replacement can easily range around $1,500 and higher, depending on the type of vehicle you drive.

If you need to buy a head gasket sealant or parts to replace your blown head gasket, we have you covered. AutoZone can supply the parts, fluids, filters, and sealants to get the job done right the first time.

If you determine the job is too big to tackle, check out our list of Preferred Shops in your area to help you complete the job.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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