What Exactly Is Head Gasket Sealer

Reviewed by

Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Written by CarParts.com Research Team - Updated on February 21st, 2024

Reading Time: 6 minutes
Summary
  • Head gasket sealer is a substance made specifically for sealing up cracks on the head gasket. You can follow the tips and tricks in our how-to section if you plan to use head gasket sealer yourself.
  • The benefits to using head gasket sealer mainly have to do with it being easy to use (although tedious and a bit more time consuming than you’d expect), and its drawbacks come with the fact that the sealer isn’t a permanent solution to a leaking head gasket.
  • When identifying a leak in your head gasket, keep a lookout for engine misfires, white smoke from your exhaust, and cooling system issues. The two common causes behind a damaged head gasket are overheating and deformed aluminum components.

Your vehicle’s head gasket is in charge of sealing your engine’s combustion chambers, preventing compression loss, as well as sealing passages that pass from the block into the head to prevent coolant and oil migration.

Head gaskets have several different failure modes, and head gasket sealer can’t help with some of the several ways head gaskets fail. 

Failures head gasket sealer can help with are as follows:

  • Coolant that enters the combustion chamber and temporarily fouls one or more spark plugs when starting the engine after a “hot soak.” This coolant disappears out the tailpipe while the engine is running.
  • Combustion that enters the coolant and causes overheating and very high pressure.

The failures head gasket sealer can NOT help with are as follows:

  • A leak from between the head and the engine block
  • A combustion leak from one cylinder to an adjacent cylinder
  • A leak that mixes oil and coolant (rare)

When you suspect that your head gasket is compromised, you’ll need to bring your vehicle to a trusted mechanic for a proper diagnosis because it’s easy to misdiagnose something else and blame it on the head gasket. If you’re a sharp enough DIY person to replace the head gasket on your own, feel free to proceed with caution. But for a quick head gasket patch in emergency cases, you might be able to postpone the inevitable with some head gasket sealer.

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: If you do decide to try some brand of head gasket sealer, make sure you follow the instructions on the container exactly or you’ll be wasting your time.

Usually, head gasket sealers require that the coolant needs to be completely drained and the cooling system needs to be filled with distilled water, displacing some of the water with the head gasket sealer liquid.

Then you’ll be instructed to run the engine for a certain amount of time, after which you let it cool down for several hours, and you drain the cooling system once more and refill with the 50/50 coolant mix.

How Does Head Gasket Sealer Work

Head gasket sealer is a substance made specifically for sealing up cracks on the head gasket. These cracks typically form between the engine block and the cylinder head. Because it closes any potential leaks, this type of head gasket seal allows you to continue driving your vehicle even with a damaged head gasket.

Products that seal a blown head gasket while the engine is running use chemicals that react with the combustion chamber heat and pressure to form a solid seal at the leak point. Again, these only work where the combustion chamber meets the water jacket. They won’t fix any other type of head gasket leak.

How long this fix will last depends on the type of sealer you use. There are temporary and permanent head gasket sealers on the market, most of which are made out of a mix of epoxy and different chemicals. Epoxy is an excellent choice of material for this job because it doesn’t dry up when exposed to the engine’s high temperatures. Temporary sealers last for a certain number of miles or months depending on the brand while permanent sealers can last for years.

Products that seal a blown head gasket while the engine is running use chemicals that react with the combustion chamber heat and pressure to form a solid seal at the leak point. Again, these only work where the combustion chamber meets the water jacket. They won’t fix any other type of head gasket leak.

Richard McCuistian, ASE Certified Master Automobile Technician

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Different brands may use different elements, such as sodium silicate, ceramic fibers, copper particles, or nanotechnology. But realize that while you have only time and a little cash invested in this process, it may not work at all, and sometimes that’s the case.

How To Use Head Gasket Sealer

When using head gasket sealer, it’s best to follow the instructions on the packaging. Here are a few tips and tricks to make the process smoother, but check the instructions that come with the product to make sure you’re doing it right.

  • Gather your materials ahead of time to avoid scrambling for them while working.
  • Lift your vehicle on a jack to make it easier to drain the coolant from your radiator.
  • Add water to the radiator.
  • Remove your thermostat before using the head gasket sealer to avoid getting sealer on it.
  • Turn on your vehicle and its heater to circulate the water and drain any remaining coolant. Drain the water as well in this step.
  • Add a fresh coolant-water mixture little by little until you reach capacity.
  • Slowly add the gasket sealer.
  • Drive your vehicle around for 30 minutes to let the sealer spread through the vehicle. Allow it to sit unused for two to three hours afterwards.
  • You can reinstall the thermostat once the sealant in the head gasket sealer is activated.

Head Gasket Sealer Benefits and Drawbacks

There are a number of benefits and drawbacks to using head gasket sealer.

Benefits

Head gasket sealers are generally easy to use and DIY-friendly. You don’t need to remove your engine from your vehicle when applying it, saving you a lot of time. They’re also fairly affordable, especially compared to a brand new engine. Head gasket sealers can be used to fix oil leaks in a pinch as well.

Drawbacks

Head gasket sealers, even permanent ones, are still only a temporary solution. It’s always best to have a trusted mechanic take care of your vehicle’s head gasket as soon as possible if it’s leaking. After all, using a head gasket sealer isn’t quite as reliable as having a new gasket. Some variants of head gasket sealer also don’t work for very long. It’s difficult to tell which of the variants on store shelves are good and which ones are bad.

How To Identify a Leaking Head Gasket

When your head gasket springs a leak, you’ll likely want to reach for some head gasket sealer. But what can tip you off to a leaking head gasket in the first place?

Well, for starters, you might notice your engine misfiring. Your vehicle will jerk about during acceleration in this case. Leaking head gaskets also lead to burning coolant as it leaks out, resulting in white smoke from your exhaust. The loss of coolant will also lead to cooling system issues and your vehicle overheating. These symptoms accompany other issues, but a blown head gasket is worth investigating if a number of them happen at the same time.

Common Causes Behind Leaking Head Gaskets

Of course, you’ll want to avoid having a leaking head gasket in the first place. Here are two common causes behind your leaking head gasket:

Overheating

Overheating can lead to the cylinder head and other metal engine parts warping, which in turn can tear the head gasket and cause a leak. To combat this, keep your vehicle’s cooling system well-maintained, and try to pull over as soon as you notice your vehicle suddenly heating up as you drive.

Aluminum Components

Certain engines are more prone to warped head gaskets. These engines often come equipped with aluminum block heads. Because aluminum alloys are more sensitive to changes in temperature, they expand and contract much more than traditional cast iron. Gasket punctures occur when the clamping force is low when the temperature is colder, so try to warm your engine up before driving if you can.

Now you know how to seal a head gasket leak with some sealer. While it does work, remember that head gasket sealer is only a temporary solution. While it’s good for getting you out of a tight bind, it’s still best to use the time the sealer buys you to get your head gasket properly repaired.

About The Authors
Reviewed By Richard McCuistian, ASE Certified Master Automobile Technician

Technical Reviewer at CarParts.com

Richard McCuistian has worked for nearly 50 years in the automotive field as a professional technician, an instructor, and a freelance automotive writer for Motor Age, ACtion magazine, Power Stroke Registry, and others. Richard is ASE certified for more than 30 years in 10 categories, including L1 Advanced Engine Performance and Light Vehicle Diesel.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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CarParts.com Research Team and Richard McCuistian, ASE Certified Master Automobile Technician