Best Radiator Sealants

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Several times in my life I have been on a tight budget and needed a fix my radiator on fast and cheap. Radiator sealant bought me a little time to get to the next pay check and sometimes last me a few months.  When your radiator leaks and you need to get to work but you don't have the money $300-$600 for a new radiator, coolant stop leak is the best solution.  


I can honestly say it's not a permanent fix but it's better than running the risk of having your car over heat and having to replace the engine.

I wrote this review because prior to the internet and google I just had to go to my closest auto parts store and buy every single radiator stop leak in the store and hope that one works.  Now we can analysis every product in the world before we buy anything. And you will find that in this review these products have different benefits that you might not expect.

Radiator Sealants Reviews

1 K-Seal ST5516 HD Multi-Purpose One Step Permanent Coolant Leak Repair

K-Seal ST5516 HD Multi Purpose One Step Permanent Coolant Leak Repair


  • No flushing or draining is required.
  • Mixes well with all types of antifreeze.
  • One-step procedure.
  • Quickly seals the leak.
  • It can be used in both hot and cold engines.


  • People complained about returning leaks after some weeks or months.

About Product:

This formula is designed for people who want to avoid all kinds of hassles. One of the biggest selling points of this product is that it is compatible with every antifreeze. Meaning that you won’t have to check or replace your antifreeze to use this product.

Easy To Use

K-Seal ST5516 is specifically designed to get you back on the road in no time. If you have discovered any leak while traveling, this sealant will work amazingly, no matter if your engine is hot or cold. On top of that, you don’t have to be a mechanical person to use this sealant. You simply have to pour this sealant into your cooling system, and you are good to go.

Universal Product

Moreover, you don’t have to worry about draining or flushing this sealant either. This sealant can be in the cooling system of your vehicle without any worry. In addition, whether you are looking for a radiator sealant for your car or tractor, this is the ideal choice. It is because this cooling system sealant is designed to suit all kinds of vehicles.

Heavy Duty

Most of the sealants you will find on the market don’t seal slightly bigger cracks. But, leaks in the radiator can be of many sizes. However, this is not the case if you choose K-Seal ST5516. This product can seal cracks of up to 1/32 inches.  

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#2 Bar’s Leaks 1186 Liquid Aluminum Stop Leak - 16.9 oz

Bar's Leaks 1186 Liquid Aluminum Stop Leak - 16.9 oz , Gray


  • Provides extra protection due to the dual protection formula.
  • Conditions all the parts of the radiator.
  • It will work perfectly with the existing antifreeze.
  • Works with water as well.
  • Shows results in 10-20 minutes.


  • Not best for oil systems

About Product:

1186 liquid aluminum stop leak is a product by Bar’s Leaks. When it comes to sealants, Bar’s Leak’s needs no introduction. For over 70 years, this company has been offering the best sealants in the market. 1186 Liquid Aluminum Stop Leak is one of the latest products by this seasoned company.

Best Protection

Bar’s Leak’s 1186 Liquid Aluminum is crafted for people who are seeking a long-term solution for their leaking radiator. This product offers a fine combination of two formulas to ensure maximum protection.

Suitable Quantity

One thing that people usually complain about is the quantity of sealant they get. Most of the sealants come in 10-12 ounces containers which are not suitable for long-term use. However, if you choose Bar’s Leaks’s 1186 Aluminum Liquid sealant, you will get 16.9 ounces. It will save you from buying sealant after every use. 

Works Even With Water

Unlike most sealants which require you to use a certain antifreeze, this product works fine even with water. There is no compulsion to use any specific antifreeze or coolant with Bar’s Leak’s Aluminum Liquid sealant.

On top of that, you don’t have to drain or flush this sealant after the job is done. This sealant is safe to reside in your radiator. In fact, it will keep servicing all the cooling system parts for prolonged reliability.

Shows Instant Results

Leaks are something that needs to be treated right away. If you notice a leak during traveling, you can’t wait to take it to the mechanic. It is where Bar’s Leak’s Aluminum Liquid sealant comes in to save the day. Simply pour this sealant into the radiator, wait for 10-20 minutes, check the leak, and get going.

It is how simple the procedure is and how fast the product works.

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3 Liqui Moly 20132 Radiator Stop Leak, 0.25 l

Liqui Moly 20132 Radiator Stop Leak, 0.25 l, 1 Pack


  • Best for hair cracks and tiny leaks.
  • Works in all both conditions, with or without a water filter.
  • No need to replace antifreeze for this product.
  • As effective as advertised.
  • Can seal cracks for several months.


  • Not a permanent solution.
  • Better suits European cars

About Product:

Who doesn’t know about Liqui Moly? This German company has made its place in the industry by providing the best fluids. 20132 Radiator Sealant is also one of Liqui Moly’s prized products.

Universal Product

Most of the time, leaks occur when we are in a hurry. In such situations, you don’t have much time to check the compatibility of the sealant. If you have witnessed a leak on the road, your direst wish will be to get going. Liqui Moly 20132 is one of the sealants that get you back on the road within minutes. All this with universal compatibility. Meaning that this product can be used with all kinds of antifreeze and coolants.

Prevents Corrosion

Leaks occur in the radiators due to rust and corrosion. This product by Liqui Moly not only seals the leaks but also prevents rust and corrosion. It extends the life of your radiator and keeps future leaks away for a significant amount of time. The radiator and this sealant also take care of the damage done in the combustion chamber by the admission of coolants.

Immediately and Easily

Liqui Moly has designed this radiator sealant to work as fast as possible without compromising its effectiveness. This product will not only do the job perfectly, but it will also save your time.  

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4 AlumAseal ASBPI12 Radiator Stop Leak Powder Blister Card - 20 g

AlumAseal ASBPI12 Radiator Stop Leak Powder Blister Card - 20 g


  • Works fine with all kinds of antifreeze.
  • Prevents leaks in the future as well.
  • Lubricates water pump.
  • Works perfectly in the water


  • May overheat the system

About Product:

If you are looking for a quick and economical solution for any small leak in your radiator, then AlumAseal Powder Blister Card is best for you. This product is one of the most effective products you will find on the market.

Easy To Carry Around

There are always chances of spillage when you are carrying liquid containers. This is not the case with AlumAseal Radiator Stop Leak, as it is in the form of a Blister card. On top of that, it weighs only 20g which is very negligible. Therefore, you can carry it around quite easily. 

Simple To Use

You don’t need any kind of mechanical background to use this Radiator sealant. You simply have to open the packaging, add the powder into the radiator, and wait for the magic to happen. No other complexity is involved in the process, making this ideal for sealing radiator leaks.  

Better Than Liquid Alternatives

The powder radiator sealant is more effective than most of the liquid sealants out there. The formula works more efficiently and forms a very minute granules protective layer.

The services the water pumps and plastic parts more impressively. Above all, powder sealants have been seen to perform better when it comes to conditioning the system. Due to this feature, rust and corrosion stay off your system for a long time.


The only drawback of this product is that it can clog the system. This usually happens when the users add more amount than the recommended quantity. This clogging in the cooling system can cause overheating.

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5 Bar’s Leaks HDC Radiator Stop Leak Tablet - 60 Grams

Bar's Leaks HDC Radiator Stop Leak Tablet - 60 Grams


  • Helps in controlling electrolysis.
  • Keeps rust away.
  • Helps lubricate water pumps seals.
  • Services overall cooling system.



  • Takes time to work.

About Product:

Bar’s Leak’s is a company that has been providing leaking solutions since 1948. In this duration, the company has evolved continuously. They have come up with some ultimate solutions to leaks in your vehicle. Bar’s Leak’s Radiator Leaks Sealants come in all three liquid, powder, and tablets form. The product we are discussing is in tablets form.

Best For Storing

If you are someone who takes all the precautionary measures to avoid inconvenience, then this product is for you. In most cases, one tablet is enough for one-time use. These tablets come in a pack of six, meaning that you can repair your leaks six times. How can you miss something this useful in your auto repair kit?

The best part is that you can store them easily until they expire due to their compact and thoughtful packaging. On the other hand, if you choose a liquid sealant, there will always be a fear of spillage.

One-Tablet Solutions

Bar’s Leak’s tablets are more than just temporary radiator sealants. These little tablets can do more wonders than you can imagine. Apart from sealing radiator leaks for a good amount of time, these tablets also neutralize pH imbalance. This feature of Bar’s Leak’s radiator leaks tablets helps maintain the electrolysis.

Moreover, these tablets form a protective layer against corrosion and rust. The features of these tablets don’t end here. These amazing tablets also lubricate all of the water pump seals.


You have to be patient with this product, and this is the only con of this product. The tablet takes time to dissolve and seal the leak. It is because the tablet comprehensively covers the leak to seal it for the long term.

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6 ATP AT-205 Re-Seal Stops Leaks, 8 Ounce Bottle

ATP AT-205 Re-Seal Stops Leaks, 8 Ounce Bottle


  • Restore the water pump seals.
  • No compulsion of flushing after usage.
  • Can condition gaskets as well.
  • Works Quickly.



  • Not very economical.

About Product:

The online ratings and reviews of ATP AT-205 Re-Seal radiator sealants say a lot about this product. This product has gained the crown by becoming the number 1 selling radiator sealant. It is all because of its unparalleled features and effectiveness. 


Restoration of rubber is one of the biggest selling points of these amazing radiator sealants. What people love about this product is that it is much more than just an ordinary sealant. This product, when added to the radiator, not only seals the leaks but also restores seals. There are a lot of seals in the radiator. In most cases, seals are the part that leaks before anything else.

This product restores the seals impressively to give a new life to the radiator.

Works Beyond Radiators

Today, you are looking for a radiator sealant. Tomorrow you could be looking for a power assembly leak sealant. When a vehicle ages, it gets prone to different kinds of malfunction. Corrosion and rusts are ever-taking processes. One day or another, you will have to find sealants for other parts leaks.

If you have an ATP AT-205 Re-Seal in the trunk of your car, you can deal with any kind of seal in the vehicle. This sealant works perfectly fine in the presence of almost all kinds of fluids. You can use it for engine, power steering, or even transmission systems leaks. 


As you might have guessed, this product comes in an 8-ounce packaging which is not suitable for multiple times use. We recommend you to buy 2-3 containers of ATP AT-205 Re-Seal at once. This will eliminate the need to source the product again and again.

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7 K-Seal ST5501 Multi-Purpose One Step Permanent Coolant Leak Repair, Blue

K-Seal ST5501 Multi Purpose One Step Permanent Coolant Leak Repair


  • No flushing or draining is required.
  • Works fine with all kinds of antifreeze.
  • It can be used for multiple purposes.
  • Fixes Permanently.



  • May overheat the engine.

About Product:

K Seal is one of the most popular brands in the sealant industry. This company has been developing quality and technologically quite advanced solutions for all kinds of leaks. K-Seal ST5501 multi-purpose, one-step permanent coolant leak repair is one of their best products.  

Shake, Pour, And Go

Yes, it is that simple. You don’t have to read lengthy manuals or take your car to the mechanic to treat the leak. Whenever a leak occurs, we start panicking and wondering how much will it cost. If we prepare beforehand by buying K-Seal multi-purpose sealant, we can avoid hefty bills.

Using this amazing formula doesn’t require you to understand rocket science either. Anyone with bare minimum knowledge of cars can use this product. You simply have to see the quantity you should pour into the radiator, shake the container, add the sealant, and go.

Treats All Kinds Of Leaks

This product is specifically designed to help you in your time of need. If you have K-Seal multiple purpose sealant with you, you can deal with all kinds of leaks. Whether the leak is in the engine, power steering, or in the transmission system, this product will take care of it easily.

This makes it an ideal product to keep in your auto repair kit all the time.

Works With All Types Of Antifreeze

In the case of this product, unlike other sealants, you won’t have to change the antifreeze of your coolant system. This sealant can work perfectly with all types of antifreeze.

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8 Bar’s Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak - 18 oz

Bar's Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak - 18 oz.


  • Conditions heater core seals.
  • Services blown head gaskets.
  • Perfect for larger leaks.
  • Can work in water alone.



  • Clogging.

About Product:

Bar’s Leak’s is a company that understands leaks to their core. They are offering the most unparalleled and the most comprehensive variety of sealants in the market. They have sealants for leaks in all places of all shapes and sizes. The product under consideration is specifically designed for larger leaks.  

Treats Larger Leaks Impressively

Sometimes we notice a leak after some time since it is developed. If you don’t get time to treat a leak or identify it when some time has passed, its size can grow. When the leaks get large, they become more difficult to treat. However, there is no need to worry because Engineers specifically design bar’s Leak’s Copper sealants to treat large cracks. 

Draining Isn’t Mandatory

Many products in the market are not safe for the radiator systems to reside in. Bar’s Leak’s Copper sealant is certainly not one of these products. If you choose to use Bar’s Leak’s Copper sealant, you won’t have to worry about flushing or draining. 

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9 J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak - 0.7 oz.

J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak - 0.7 oz.


  • Prevents future rust and corrosion.
  • The formula includes finely-grounded compounds.
  • Non-toxic.
  • Economical.



  • Some users have complained about clogging.

About Product:

JB Weld is yet another brand that you can easily trust to fix cracks. PERM-O-Seal is a product of JB welds specially designed for sealing radiator leaks. You can buy this product easily from any auto repair shop or online.

Non-Toxic Formulation

This is the best option, whether you want an instant repair or looking for a sealant to add to your auto repair kit. The product is not toxic and is dry, meaning that you can store it for quite a long time.

Finely-Grounded Compounds

The product is designed to lessen your problems and not to increase them. The formula of JB Weld PERM-O-Seal includes finely grounded compounds. These compounds effortlessly become part of your coolant system fluid and fix the leaks.

Permanent Solution

Buying JB Welds not only means that it will save your trip, but it will also keep you away from the repair shop. The company claims that this is not a temporary solution; it is very reliable. Hence, if you want a credible long-term solution for your vehicle, this is the product to go for.


Users of JB Weld PERM-O-Seal have stated that they have faced clogging after the use of this product. However, this could be because of not following the instructions given by the manufacturers.

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There are many radiator sealants to choose from especially when you are shopping on Amazon. Because of people like me I hope you can make a better decision.  I think the most important thing to consider is the type of leak and the symptoms.  If its a big leak go with something like Bar’s Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak - 18 oz or if rust is a concern try Bar’s Leaks HDC Radiator Stop Leak Tablet - 60 Grams.  Just act as quickly as possible because if your car over heats it could ruin the engine.  Also keep in mind that these are only temporary so its important to monitor your radiator closely after you use any Stop Leak.

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