What Is The Best Head Gasket Sealer?

Just want a quick answer? I choose Bar’s Leak HG-1 as the best head gasket sealer. It’s priced well, is a permanent fix, and you may not need to flush your coolant system unlike others.

After graduating college I was living in a house that I was renting. I had just moved in and the house owner called me one afternoon. He told me that my car was leaking oil onto his driveway and he didn’t like it.

I wouldn’t like it either if it was my driveway.

I took a look and sure enough, there were some oil spots on the concrete. I inspected the engine all over and finally determined the source of the problem. It was the head gasket in my beloved Mitsubishi Eclipse. I figured I needed to replace the gasket.

It took forever. An entire Saturday actually.

I was young then and didn’t know any better. If I had known there was a quicker fix, I would have chosen it then.

What’s the Benefit of a Head Gasket Sealer?

You Can Do It Yourself

The sealer comes in a bottle and you pour it in the radiator. It’s as simple as that. Run the engine and it will seal any leaks once the engine heats up to temperature. You don’t have to take it to a professional to check out the issue.

It Will Save You Time and Money

It is so much easier to use a sealer than completely replacing a head gasket. Pour the sealant in the vehicle’s radiator cap and it will flow through the vehicle’s entire system to plug leaks. It is a fast process and will seal any holes in few minutes.

The sealer itself is less expensive than having a mechanic replace the gasket. If you have a mechanic do it, the labor is the most expensive part. The actual gasket itself is not expensive at all. The sealer is an inexpensive alternative that is also a permanent solution.

It’s a Multi-purpose product

Not only will it help you fix the main problem, but you can also use it to fix other issues that can impact performance. Other uses include sealing radiators, engine blocks, freeze plugs, and heater cores.

What Else Should I Know?

It May Not Fix All Leaks

Sometimes engines and cooling systems can have large holes in places we can’t see. These products work on the molecular level and won’t plug every hole. You may try this fix and it won’t work.

So be prepared. But it’s a cheaper option than having a mechanic replace your head gaskets.

These products may also cause problems if your cooling system is dirty or contaminated. Some manufacturers recommend flushing the cooling system before adding the sealer. Others say you don’t have to flush it.

Just know that you may make a bigger problem if you stop up your radiator hose and clog the entire system.


The liquid is measured in ounces ranging in quantity from eight ounces to a few gallons. Make sure you get enough sealant that it will take care of your vehicle’s issues. If you have a small engine, a 8 ounce container can seal up to a 20 liter engine. This is enough to cover most situations. For older vehicles it may be good to keep a small container in your vehicle for emergencies.

You don’t wan to add too much either. This can cause clogging and other major issues like having to replace the radiator. Read the instructions to determine the right amount to add.

Working Time

Make sure the engine is cold before opening the radiator. Never open the radiator on a hot engine. You could injure yourself with hot liquid. Once you’ve poured in the sealant, start the engine and let it warm up. You can drive it slowly or just let it idle. Once it’s warmed up, the process is usually complete and you’ve got a permanent fix. Some products finish working once the engine warms up and others will need up to an hour.

Bar’s Leak HG-1

HG-1 uses a non-clogging formula for great performance. It’s made with a carbon fiber formula that can plug leaks without clogging the heater core. It’s affordable and you can use it to seal more than cracks and gaps.

This is an effective and easier solution than replacing your head gasket. It features a carbon fiber formula that can plug leaks without clogging the heater core. It’s compatible with diesel, gasoline, and racing engines. It also prevents water overheating thanks to its Xtreme Cool formula.

Add it directly into your coolant. The instructions say there isn’t any flushing or draining required. But if you think your cooling system may be blocked or contaminated, you’ll want to flush it first. You’ll make things worse if there’s stuff in your coolant that shouldn’t be there.

If you drain your cooling system refill it with a mixture of 50% water and 50% antifreeze. Then add HG-1 according to the instructions.


  • It meets ASTM D3147 (Standard Test Method for Testing Stop-Leak Additives for Engine Coolants).
  • This is a very affordable option.
  • It’s very thick and will seal any holes easily.


  • It may come out very slow and you’ll have to wait a bit.
  • Some people mention it clogs their cooling system after adding it. I suspect they already have some particles or fragments in the system.

BlueDevil Head Gasket Sealer

BlueDevil Head Gasket Sealer not only seals leaks but also binds cracks. This helps to prevent pressure from becoming trapped in the cooling system. This product doesn’t contain any harmful chemicals and won’t damage other parts of the car or engine. It will help prevent your engine from overheating and keep it’s temperature in range.

This is a good option for both 4-cylinder and V6 engines. This product doesn’t contain any particulates or fragments that can cause issues in a coolant system. It can also seal and repair freeze plus and heater cores. Safe and easy to use, it has a pour and go design.

The BlueDevil Head Gasket Sealer is a great alternative to costly repairs. You will need to pour the contents in 1 minute, no faster. Pour slowly.


  • It has no fragments, particulates, or solids that clog coolant system.
  • It works with both gas and diesel engines.


  • You need to flush your radiator first before adding this product.

Steel Seal Head Gasket Fix

Steel Seal is a good option if you want a product that lasts longer than others. Most other liquid head gasket products use a mixture of sodium silicate. People call it liquid glass.

This product is made with a proprietary mixture of chemicals. These chemicals bond to metal and create a molecular seal. This bond expands the same way metal does when heated. This bonding difference is what makes the repair last longer than other products.

This option comes with two bottles and is the right amount for six cylinder engines. The included instructions are easy to follow but it will help if you have a little automotive knowledge. There are no particles that could cause blockages or build up in other areas. It works with both gas and diesel engines.

The downside is that it’s a little pricier than other products. You’ll also need to flush the cooling system.

This is a good choice for larger engines, second-hand vehicles, and old trucks.


  • It comes with two bottles for 6 or 8 cylinder vehicles. You may have some left over.
  • The fix will last longer than others due to its proprietary formula.


  • It’s not compatible with antifreeze formulations.
  • You need to flush your cooling system before using it.
  • It’s more expensive than other options.

K&W FiberLock

This is a sodium silicate formula with nano-fibers added to it. It’s compatible with any type of antifreeze. K&W says the fibers are military strength. I’m unsure of how that’s measured and what qualifies as military strength. The fibers will create layers of webbing over the crack and interlock together.

It’s also a permanent fix that is easy to use. Pour in the repair formula. It will fix cylinder heads, cooling systems, engine blocks, and head gaskets.

There is no need to drain or flush your system with this formula.

Cool-X Conditioner lowers the coolant temperature when it circulates throughout the system.


  • The nano-fibers and particles will create a stronger bond.
  • It works with all antifreeze and coolant.
  • The instructions mention you don’t need to drain the coolant already in your system.


  • Some people pour in the entire bottle and cause more issues. You won’t need a whole bottle for a standard car.

K-SEAL Ultimate

K-Seal is an option if you don’t want to drain your cooling system. It uses a blend of chemicals made of copper particulates and ceramic microfibers. These fibers will bond to each other when forced through a hole. They’ll form a bond and block the liquid from escaping. Engine heat then cures the bond even further.

This is a multi-purpose formula that stops leaks in heater cores, radiators, cracked blocks, or head gaskets. It’s compatible with all antifreeze products and is intended to “pour and go.”

K-Seal states you are not required to flush the coolant system before adding it.

You don’t need special skills or knowledge to use this sealant, but keep in mind that it only works for minor leaks. The sealant works fast, is effective, and affordable.


  • This is a very affordable option.
  • It meets ASTM D3147 for leak tests.
  • Seals very small holes of 0.635mm diameter.
  • It’s good for both gas and diesel engines.


  • Some people say it doesn’t work for them. It’s possible the holes and leaks were too large.


I like Bar’s Leak HG-1 the best. It’s affordable and takes only one dose to stop most common leaks. You don’t have to flush the cooling system although I would recommend it just to be safe. It’s a permanent sealing solution and works fast.

If you’re in a situation where the gasket repair costs more than what your vehicle is worth, it’s time to take matters in to your own hands. This is one of those problems that you can fix yourself with a specific product.

Bar’s Leak HG-1 will save you time, save money, and you can do it yourself.

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