The Best Radiator Stop Leaks For 2023

Imagine you parked your car near a shopping mall and discover a pool of liquid beneath your vehicle after you get back from shopping. No denying that’s going to be the worst and most frustrating discovery for you. The leakage can turn out to be expensive, especially if the radiator needs repair or replacement. In such cases, you have two options. First, you call a professional automobile repair agency and have your radiator replaced. Second, you fix it on your own.

Replacing your radiator is not an ideal solution when you have all those shopping bags in your hand. Moreover, it can be a time-consuming and expensive job. So, the best option is to seal the leak on your own. To do that, you will need the radiator stop leak sealant. It is available in both liquid and tablet form. Radiator stop leak sealant is used to seal the part that’s leaking. It also forms a robust layer around the seal so that the radiator does not face further damage.

What Is Radiator Stop Leak Sealant?

Radiator stop leak sealant is one of the easiest leak repairing solutions. You could apply it straight to your car’s cooling system to stop the leakage and form a protective layer that keeps the radiator safe from possible leakage.

Some radiator stop leaks sealant can be applied directly into the cooling system, while others require the system flush before the sealant is poured into the radiator.

Another important thing to note here is that radiator stop leaks sealants are advertised as the 100% permanent solution for your car leakages and radiator problems. Well, that’s not true. Though the radiator stop leak sealant is an effective option to seal the leak on your radiator, you will have to address the main leakage problem later. This is because if you don’t look into the root cause of leakage and the main problem persists, there is a good chance the leakage will return at some point. The size of the leak also matters. If you notice a significant amount of water leakage under your vehicle, then this indicates a bigger problem.

So, before we go ahead, make sure that the radiator stop leak is going to be a cheap and quick fix to your leaking radiator. However, you must not consider it as a permanent solution to the issue. Now, selecting the best sealant can be an overwhelming choice considering an extensive range of sealants available in the market. So, in this post, we will mention some effective leakage sealants that can offer durable and quick repairing services. Let’s have a look.

1. AlumAseal ASD Radiator Sealer Tuber Dispenser

AlumAseal ASD Radiator Sealer Tuber Dispenser is sold in the powder form. It offers one of the fastest and easiest seals around the radiator. The manufacturer has guaranteed that the sealant will not clog the radiator. You don’t need to drain the existing coolant. Being compatible with anti-freeze solutions, it can be poured directly into the radiator.

It is a perfect choice for most vehicles as the chemical compounds this sealant is made of are compatible with plastic, metal, and even tuber radiators. This USA-made sealant works wonders in a matter of minutes. Remember that you remove the radiator cap only when the engine has turned cold. It prevents corrosion, leakage, and other radiator damage. It even lubricates the water pump. Ease of use is probably the first thing car owners look for in a radiator stop leak sealant. AlumAseal ASD Radiator Sealer Tuber Dispenser is an ultimate solution if the application is your main concern.


  • Prevents leakage
  • It doesn’t clog the system
  • Compatible with coolants
  • It works with metal, plastic, and rubber systems

The Pros

  • Easy to apply
  • Quick solution
  • Compatible with different materials

The Cons

  • Offers temporary solution

2. Bar’s Leak Liquid Aluminum Stop Leak

Bar’s Leak Liquid Aluminum Stop Leak is an effective and the strongest radiator stop leak sealants on the market. It can seal gasket, radiator, and heater core efficiently. The sealant uses Xtreme Cool as well as aluminium (liquid) to adjust the temperature of the coolant. Not only is it known for forming a strong seal around the cracks and pinholes, but Bar’s Leak Liquid Aluminum Stop Leak can condition the radiator. It repairs all sorts of leakages and keeps your radiator from rust.

The best part about this sealant is its compatibility with coolants and anti-freeze solution. You don’t need to drain the radiator before applying Bar’s Leak Liquid Aluminum Stop Leak chemical. You could also use this formula with water, but you will need to pour an additional bottle of aluminium. The compound is compatible with all kinds of anti-freeze and coolant solutions. Usually, the leak is sealed almost instantly after the application. But, in some cases, you may need to drive the vehicle for 20 minutes for the compound to circulate around the radiator seamlessly.


  • Seals gasket, heater core, radiator, and freeze plug leaks
  • Condition the radiator
  • Compatible with antifreeze and coolants

The Pros

  • Easy application
  • Durable
  • Faster results

The Cons

  • Only 1 bottle is available in the package

3. Ironite All Weather Seal

Ironite All Weather Seal is one of the easy-to-use and high-quality radiator stop leak sealants. The application process is super simple. You only need to pour the formula into the radiator, without having to drain the coolant. Compatible with gasoline and diesel engines, you can use this sealant on all types of cars and radiators. The compounds are dissolved in the radiator, avoiding the risk of unwanted clogging in the system.

As the name implies, the solution is quite effective regardless of the weather. Even though it is a little expensive than the other compounds mentioned on this list, the convenience and quality results are worth every penny you spend. Ironite All Weather Seal is a reliable and versatile radiator stop leak sealant. Whether you are a professional mechanic or a car owner, Ironite All Weather Seal can help fix all types of radiator leaking issues in no time.


  • Universal compatibility
  • Mixes with anti-freeze
  • It doesn’t clog the radiator

The Pros

  • All-weather design
  • Works well with diesel, propane, and gasoline engines
  • Compatible with coolants and anti-freeze
  • Easy application

The Cons

  • Expensive

4. K-Seal ST5501

It blends well with the anti-freeze and coolant solution to offer a long-lasting seal. K-Seal ST5501 Multi-Purpose Permanent Radiator Stop Leak Sealant is a tried and tested product. The product is made of microfibers that build a strong mesh around the pinholes and cracks that cause leakages.

What sets this product apart from its counterparts is the strong mesh that gives permanent results. It has the ability to repair the leakage of 0.635 mm. Though it is a strong solution containing microfibers, rest assured the K-Seal ST5501 Multi-Purpose Permanent Radiator Stop Leak Sealant won’t clog your system.

This 9.6-ounce bottle can be poured directly into the radiators. You don’t have to drain or empty the coolant. Plus, you only need to shake the bottle and it is ready to use. It is quite portable. But, it is extremely important for car owners to read the manufacturer’s instructions properly and ensure that the product is compatible with your specific radiator and engine.


  • Blend of ceramic fibres and copper particles
  • Scientifically tested
  • Permanent seal guaranteed
  • Fixes different types of leaks

The Pros

  • Offers permanent seal
  • Compatible with antifreeze and coolants
  • Easy application; no need to drain the coolant
  • Inexpensive
  • Multiple applications
  • Strong compounds

The Cons

  • No cons that we know of

5. Zerex Super Radiator Sealer

Zerex Super Radiator Sealer is the best option for car owners who want to stay prepared for unpredictable radiator damage or leakage out of nowhere. The product can be used for multiple applications. The water-based solution is 100% compatible with different materials. The company claims that the product seals all sorts of cracks and holes in less than an hour. It may not offer the fastest results. But, performance-wise, it is an ideal radiator stop leak sealant.

Though it isn’t one of the renowned brands on the radiator stop leak sealant market, Zerex Super Radiator Sealer does a fantastic job when it comes to repairing the radiator leakages.


  • 12 case bottles option
  • Compatible with natural materials
  • Offers quick fix
  • Authorized for professional automotive repair

The Pros

  • Decent performance
  • Can be used on multiple radiators
  • An effective option for urgent sealing requirements
  • Durable
  • Versatile

The Cons

  • In rare cases, it can clog the heater core
  • Slow performance

6. ATP AT-205 Re-Seal Stops Leaks

Do you want a sealant that offers quick radiator repair services? ATP AT-205 Re-Seal Stops Leaks repairs the rubber gaskets, radiator, and leakage in different parts seamlessly. No need to worry about flushing out the radiator. It can be used with hydraulic and synthetic oils, gear oil, and power steering fluids. The sealant is hard enough to repair dry and leaking areas in your radiator. The best part is that it doesn’t clog the components. Rest assured that ATP AT-205 Re-Seal Stops Leaks cause no damage to the radiator’s interior components.

The application of the product is quite simple. You only need to pour the solution into the radiator. The formula will easily blend with all the above-mentioned oils. You need to run the vehicle so that it blends faster and circulates around the radiator for efficient results. AT-205 is specially used in the manufacturing of rubber. It makes it harder while adding the required level of flexibility. The worn or dried gasket needs a chemical solution that could rejuvenate it. ATP AT-205 Re-Seal Stops Leaks does the same. Given that the gasket isn’t damaged severely, it will be resealed in 5 hours.


  • Restores the seal and flexibility of the gasket
  • Compatible with different oils
  • Professional strength
  • Works well for worn and dried gasket seals

The Pros

  • Easy application
  • Rejuvenates gasket seals
  • Seals severe leaks
  • Universal compatibility
  • Conditions the radiator

The Cons

  • The results can take up to 5 hours

7. Blue Devil Radiator and Block Sealer

Car owners looking for a permanent solution to their radiator leakage can opt for Blue Devil Radiator and Block Sealer. The sealant is available in liquid form. Now that it doesn’t contain any fibrous substance, you don’t have to worry about the radiator or the components getting clogged. Compatible with plastic, rubber, metal, and aluminium, Blue Devil Radiator, and Block Sealer is an ultimate option for all types of radiators.

Its permanent repair ability justifies the high price tag. Whether you have gasoline or diesel engine, rest assured Blue Devil Radiator and Block Sealer will seal the leakage in the radiators, gasket, and other areas for good. It is better to spend a few extra bucks for premium products than buying multiple bottles of low-quality sealant that won’t work. This sealant is one of the most impressive products for all types of engines and radiators. No need to flush out the system before application. Just pour the solution into the radiator and expect the best results.


  • Permanent repair solution
  • Guaranteed satisfaction
  • Free of fibrous materials
  • Compatible with plastic, metal, and other materials

The Pros

  • Easy application
  • Safe
  • Universal compatibility
  • Permanent seal
  • Doesn’t clog the radiator

The Cons

  • Expensive

8. Presone AS120 Radiator Sealer – 11oz

Presone AS120 Radiator Sealer – 11oz is designed to help solve the radiator problems in no time. The strong compounds form a robust mesh in the radiator, sealing all the pinholes and cracks effectively. Though its leak sealing capacity is up to 0.5 inches, it can be used for larger holes as well.

The product causes no harm to the internal component of the radiator. Rest assured the Presone AS120 Radiator Sealer – 11oz will do its job without clogging the radiator. It has multiple applications ranging from the heater core to the water pump. Made of premium synthetic materials, the formula can form strong seals that last forever. In addition to treating the leaks, the compound fixes corrosion and worn components in the radiator. It delivers quick and effective results. It restores the flexibility and strength of the radiator by sealing all types of cracks and leakages in a matter of minutes.


  • Seals leakages in the heater core, water pumps, and car radiators
  • It doesn’t clog the internal components
  • Made of the combination of synthetic and natural compounds
  • Effective on 0.016 x 0.5 inches leaks

The Pros

  • Treats large cracks and leakage holes
  • Treats corrosion
  • Permanent seal solution
  • Quick results
  • Multiple applications

The Cons

  • Expensive

9. J-B Weld DS-114 PERM-O-Seal Radiator

An ultimate option for mechanics and car owners, J-B Weld DS-114 PERM-O-Seal Radiator features 2 bottles of radiators and plastic repairs. The instructions are clearly mentioned in the package. Moreover, the application is quite simple. If you are a DIY person, you will find it super simple to use. It can be used in fluid tanks, storage tanks, radiators, and water tanks.

The USP of the brand is its permanent repair solution. It works on all types of water tanks and radiators, except for the aluminium radiators. It is a viable option for car owners searching for a quick repair kit for the leaking radiator. It is considered the go-to repair kit for car radiators. Should you observe the pool of liquid beneath the car, pour this solution into the radiator and get instant results.


  • Permanent seal solution
  • Used for multiple purposes
  • 2 containers
  • Durable

The Pros

  • Speedy solution
  • Easy to pour
  • Versatile
  • Nontoxic compound
  • Offers 2 containers
  • Compatible with different applications

The Cons

  • It doesn’t work on aluminium radiators

10. Genuine GM Fluid 3634621 Seal Tablet

Genuine GM Fluid 3634621 Seal Tablet is another effective leakage repair solution. It is available in tablet form. It is an ideal option for car owners or automobile store owners looking for an affordable radiator stop leak sealant.

The formula is specially designed for different types of radiators and engines. We highly recommend you check its compatibility with your model before making a purchase. In addition to forming a strong mesh around the cracks and pinholes, Genuine GM Fluid 3634621 Seal Tablet has the ability to fix all types of leakages in a matter of minutes. Not only does it work for leakages, but the formula is strong enough to fight corrosion.

As far as the safety of the radiator is concerned, the formula is made of 100% non-toxic materials. It doesn’t clog your system.


  • Made of non-toxic materials
  • It doesn’t clog your system
  • Compatible with DEX-COOL
  • Made specifically for automotive application
  • Can be used for all vehicles

The Pros

  • Non-toxic product
  • Universal compatibility
  • Automotive application
  • Seal minor and major leaks

The Cons

  • No cons that we know of

Guide to Buying an Effective and Quality Radiator Stop Leaks Sealant

For your car to run smoothly, there are certain components in your vehicle that are supposed to work properly. If the radiator acts up or leaks, your car engine will break down and it won’t function until the radiator is replaced. The job of the radiator is to cool your car’s engine with the help of a quality liquid coolant.

The common reason for the engine break-down is overheating. Coolant protects the engine from overheating issues. But, a leakage in the radiator could empty the liquid coolant from the radiator and damage your car engine. To avoid this leakage and prevent corrosion, you will need to invest in a high-quality radiator sealant for your car. 

As mentioned above, the market is full of a wide range of radiator stop leak sealants offered by different brands. Choosing the best one could be a daunting task, especially if you have never used a sealant before. But, fret not! Here, we have mentioned some important factors to take into consideration when shopping for a radiator stop leak. Let’s have a look:

Can You Do it On Your Own?

Fixing the radiator with a sealant is as simple as pouring the solution into your car radiator. Still, it is best to consider whether you will be able to do it on your own or you want professional help. If you do not know about the gasket or vehicle’s radiator, then it is best to leave the job to professionals.


The sealant for leakages can vary by price. You are going to have to compare the price of different sealants before buying the product. Not everyone has the budget to buy the most expensive and permanent radiator sealant solution. Sure, there are low-priced sealants available, but it may compromise the quality of the repair. The best thing you could do is check the features, read customer reviews, and invest in the sealant that offers the best services at a reasonable price.

While price does matter, it is absolutely fine to spend a few extra bucks for a quality sealant that offers a secure seal. It is the quality that matters. Low-quality and cheap products may help fix the cracks temporarily. But, you will eventually need to replace the radiator if the leak persists.


As mentioned earlier, the sealant can be applied directly to the radiator and mixed with the remaining coolant solution. However, some sealants require you to flush the radiator thoroughly and drain the existing fluid before pouring the sealant solution into the radiator. If you plan on investing in an easy-to-use and convenient sealant, then the one that doesn’t need radiator flushing will be an ideal option. Make sure you double-check the application process before buying the solution.

When the sealant is poured into the radiator, it blocks the small pinholes in the system that causes coolant leakage. The chemicals in the sealant are strong enough to seal these tiny holes in the radiator for good. However, if you buy the sealant that needs to be drained after a short while, there is a high possibility the pinholes that were blocked will return. In short, the problem is going to persist if the sealant is emptied from the radiator.


Not every sealant that claims to offer 100% permanent and effective solution will be compatible with your model. If you don’t check the compatibility of the sealant and pour an incompatible solution into the radiator, then it will damage the radiator as well the engine.

Usually, the manufacturers mention the model the particular sealant is compatible with. So, it is your responsibility to check this information beforehand.

Speed of Performance

You purchase the radiator stop leak sealant to fix the leakage as quickly as possible. Of course, you will want to invest in a sealant that stops the leakage as soon as the solution is poured into the radiator so that it doesn’t drain coolant anymore.

A quality sealant is the one that not only saves you some bucks on a replacement but is saves the repair time by speeding up the process. Check how much time the sealant needs to function and repair the cracks and holes in the radiator after the application. If you purchase a trusted brand, there is a good chance the sealant will repair the leakage faster than usual. Pick a product that gets you out of this mess as soon as possible.

Trusted Brand

Buying the cheapest radiator stop leaks sealant is going to be a waste of money and your efforts. It could even lead to further damage to your radiator. So, the price shouldn’t be the only factor to consider when buying a sealant.

It is equally important for car owners to check customer reviews and make sure you are buying the sealant from a brand that has a stellar reputation in the market.


Of course, there must be leakage and a pool of liquid underneath your vehicle. That’s the reason you are buying a radiator leak stop sealant. But, are you certain the leakage is from the radiator? It is best to be 100% sure before you purchase a sealant. So, double-check the radiator before making a purchase.

Another important factor to consider is the size of the leakage. If there is a significant amount of liquid draining from your radiator, then there is a severe leakage in your radiator. Now that the problem is bigger, you will need to pour twice the amount of liquid to seal the radiator. We highly recommend you get professional help with heavy leakages to get it repaired properly.

For small leakages, one bottle of the sealant will suffice.

Steps to Apply the Radiator Stop Leak Sealant

You can save some bucks by applying the sealant on your own. Here is the step-by-step guide to repairing your car radiator with the radiator stop leak sealant.

  • Check the Size of the Leak – Do you observe the puddle under your vehicle? Well, that is the first sign indicating a problem in your radiator. The engine is overheated when the coolant does not function properly. To confirm the leak, remove the radiator cap and see if there is any uncommon change in the coolant level. Open the cap only when the engine cools down. Visual inspection of the radiator is necessary before you look for the repair options.
  • Opt for a Reliable Sealant – Remember that the product you pick has a great impact on the repair of the radiator. In order to solve the problem, you must choose a high-quality radiator stop leak sealant that forms a hard bound. We recommend you buy the tried and tested solution for the best results. Go for a trusted brand only (even if you need to pay extra).
  • Read the Application Instruction – The radiator stop leak sealant compound is made of different chemicals. That said, the application of these sealants will vary depending on the product you choose and the compounds it is made of. The product comes with a clean manufacture guide on how to pour the solution into your car radiator. It is extremely important to read the instructions before applying it.
  • Pour the Solution into the Radiator – Check the recommended dosage and pour the solution into the radiator accordingly. Depending on the intensity of the leakage or damage, you may need to pour one, full bottle of the sealant. You may or may not need to empty the coolant from the radiator first. The instructions will be mentioned in the product package.
  • Start the Engine – Running the car will ensure that the sealant has circulated around the leakages. It is important to warm up the engine to test the radiator.
  • Fill it with Water – Once you are done with the process, the next step is to fill the system with 50% of both water and coolant. This cools down the radiator. Allow it some time to sit (probably 12-15 hours).

Final Words

The radiator stop leaks can vary by compounds and types. You will also find certain brands that have established a great reputation for offering high-quality and sturdy sealant. These companies claim to offer products that fix your car radiator in a matter of minutes. The sealants also vary by the application process.

The sealants can seal all types of radiator leakages. You only need to pour the solution into the radiator and the leakage will be fixed. However, if you still notice a puddle under your car, then there is more leakage to fix. This will also imply that the application did not work. If that happens, you need to take your vehicle to a professional.

Common Questions & Answers

  1. Is it Possible to Fix the Car Radiator with Sealant?

    Yes, a premium radiator sealant is capable of sealing the cracks or pinholes in the radiator that causes leakage. There are many brands offering premium sealant that claims to treat the leaking radiator. Usually, car radiators are prone to natural wear and tear. If the radiator acts up or forms crack, then the coolant solution you had poured into the system will leak. As a result, it will break down your engine.

    The stop leaks are sold in liquid, tablet, and powder form. It is one of the cheapest ways to repair the leaking radiator. The replacement is also an option, but it is only recommended for radiators that are damaged so much that repair doesn’t even seem an option. Note that the replacement of your car radiator is expensive.

  2. How Does the Radiator Stop Leak Sealant Work?

    As soon as the solution is poured into the system, the ceramic particles present in the compound travel across the radiator. When the radiator is under pressure, the filler ceramic particles travel around the pinholes and cracks that leak. The pressure in the cooling system combined with the ceramic particles plugs these cracks and gaps. That is how it seals the leak.

    In rare cases, the sealant forms a permanent seal that doesn’t need to be emptied and refilled. So, make sure that you flush down the coolant every now and then and pour fresh sealant compound into it. However, some companies have started to use nanotechnology that offers tiny fibres. These fibres are similar to the ceramic fillers. The only difference is that the tiny fibres develop a net around the leaks that is strong enough to cure the overheating issue for good.

    Some sealants, made of sodium silicate, work by melting the particles to create a mesh. The sodium silicate keeps melting and re-melting to produce a hard net around the cracks and holes. This seal is permanent. That’s the reason why companies have started manufacturing radiator stop leaks sealant with the combination of metallic ceramic fillers and sodium silicate.

  3. What Leads to Leakage in the Car Radiator?

    Radiators tend to face wear and tear over time. So, one of the most common causes of this leakage in the radiator and other damages is the owner's negligence. You are supposed to change the coolant according to the manufacturer's instructions. If you do not follow the radiator coolant instructions, the system will start to corrode over time.

    In most cases, the leakage problem isn’t because of some small crack in the radiator. In fact, it is a bigger problem that can’t be fixed with the sealant. As mentioned above, most sealants form temporary seals around the cracks. However, if you look into the matter as soon as possible and fix it with the sealant, there is a good chance the chemicals will form a hard seal.

    To avoid the leakage and any sort of damage to the radiator, it is important for car owners to change the coolant occasionally or as recommended by the manufacturer.

  4. What is the Cost of Repairing Radiator Leakage?

    The actual cost will depend on the brand you choose and the level of damage in your radiator. If the radiator needs higher maintenance, then the mechanic will add a few extra bucks to your repair bill. You can save this cost by fixing the leakage on your own.

    You only need to pour the coolant solution into the radiator. In some cases, the existing coolant compound needs to be drained before the sealant is applied. But, the application process is straightforward. You don’t need to take the radiator to the automobile shop unless you have zero knowledge of repairing the radiator. If you do it yourself, the total cost you will incur is the cost of the repair kit only. It will be around $45 to $100.

  5. How Many Sealant Bottles Do I Pour?

    The amount of sealant you need to pour into the radiator will vary by the product. Each sealant contains different compounds. You need to check the label and read the manufacturer's guide to know the amount of sealant required. Usually, the dosage recommendation is mentioned in the package. If it is not mentioned, contact the seller or discuss it with an automobile expert.

    Basically, the experts recommend dosage according to the severity of the leakage and your model. If you observe the giant pool of liquid under your vehicle, then you might need multiple applications for a stronger mesh. It is better to purchase extra products in advance so that you will have the sealant handy if needed.

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Louis Jones

Cars have always played an important role in Louis' career. After working full-time at Toyota and Ford for over 12 years combined, he decided to take some time off and instead focus on helping automotive owners online. With his vast knowledge and expertise about cars, motors, and engines, he quickly ended up as the leading writer here at CarGuided.