The 10 Best Radiator Stop Leaks to Buy 2019

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Even though most radiator stop leaks only offer a temporary fix, the fact that they can save you after getting stuck in the highway with a leaking radiator is a huge plus. With multiple radiator stop leak options available, the only problem any car owner would have is finding one that works as advertised. There is no denying that a radiator stop leak (when used appropriately) can save you time and money.

In this post, we take you through some of the best radiator stop leaks we could find. But first, let’s look at some features you should consider before making a purchase.

Features to Consider in Good Radiator Stop Leaks

Does it mix well with anti-freeze?
While some stop leaks will require that you drain your cooling system after application, some are designed to mix well with your coolant without causing any problem. You need to go with a stop leak that mixes well with your anti-freeze and here is why. When you add your stop leak into the radiator, the solution contains chemicals that plug the tiny pinholes that have formed in your radiator. If the stop leak requires that you drain your system after some time, there is a high chance the leaks will return as soon as you drain the system.

Speed of performance
Apart from the fact that a decent stop leak can save you a couple of bucks, time is also a factor and a good stop leak will help you save some of that as well. That is why you need to look at how fast your stop leak can seal those cracks in your radiator. A fast perforating stop leak can take you out of a mess in no time.

Budget
Most stop leaks are affordable. However, just like any other product, once you decide to go with a low priced product, the chances of compromising on the quality increase. It’s a good idea to spend extra on a quality stop leak that will not clog your cooling system or leave any traces of sludge in your engine.

Compatibility
Most car owners and professional mechanics stay away from stop leaks due to the risk of damage to the engine. While this is a valid concern, not all stop leaks are harmful. The idea is to find a stop leak product that is compatible with your radiator. You can check the instructions that come with your stop leak to confirm compatibility.

Ease of use
When you decide to pick a stop leak, check to see whether it is easy to use. You can also choose to have a professional mechanic apply the stop leak to your car if you are not sure what to do. However, most stop leaks are easy to use. We have added a ‘how to’ section on our guide below the list with steps on how to apply a stop leak to your radiator.

Brand
The last thing you need, especially after confirming that your radiator is leaking, is to have a low-quality stop leak ruin the rest of your cooling system. We recommend going with a brand that is known for producing quality products. In our list, we have included products from brands with a stellar reputation in order to make your work easy.

Size of the leak
First of all, you should not neglect any signs of a leaking radiator. The earlier you seal up a leaking radiator the better it is. Keep in mind that radiator stop leaks are not entirely designed to be a permanent solution to a leaking radiator. Therefore try to seal the leaks while they are still small. If you have a large leak in your system, the best solution is to seek professional help or go with a stop leak that is capable to tackle larger cracks.

Top 10 Best Radiator Stop Leaks 2019

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

Why we like it: Among all the reasons to get a radiator stop leak, cutting costs is by far one of the main reasons for most car owners. The K-Seal ST5501 is designed to go beyond affordability to ensure all your holes and cracks are sealed.

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Design and performance
This stop leak repair comes in a liquid form and it mixes well with the anti-freeze to provide a long lasting fix. One of the reasons this product is trusted by many customers is the fact that it is scientifically tested to prove that it works. It contains microfibers that make contact with the cracks to forms a mesh that seals the radiator effectively.

Convenient features
What makes the K-Seal ST5501 stand out is the fact that it can seal holes as big as 0.635mm. Plus, it’s designed to prevent clogging so that you can use it with peace of mind knowing that it won’t cause any damage to your engine. Furthermore, the mesh seal that this stop leak creates around the holes of your radiator are extremely strong making this the ideal stop leak for those seeking a permanent solution.

Verdict
There are a few stop leak products that deserve the number one spot in any list and the K-Seal ST5501 is one of them. It is pretty easy to use and it requires no flushing or draining. As an emergency stop leak its compact 8-ounce bottle makes it convenient to carry around while on the road. However, like all stop leaks, it is important that you check the instruction to make sure it’s compatible with your car’s engine.

Pros
  • The best option for a permanent repair
  • It can be used on gaskets and cylinder heads as well
  • Works well with all anti-freeze
  • It does not require draining or flushing after use
  • Affordable
Cons
  • Some customers complain that it clogged their radiator

2. Blue Devil Radiator & Block Sealer

Why we like it: If you are looking for a premium pack that does not disappoint, look no further than the Blue Devil Radiator & Block Sealer.

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Design and performance
The Blue Devil Radiator & Block Sealer is one of the best stop leaks out there for a permanent repair to your radiator. It comes with a safe and easy-to-use design that is in liquid form. Made with a special formula that does not contain any solids or fibrous material, this stop leak guarantees not to clog or harm your radiator which is amazing. Plus whether you radiator is made of plastic, metal or aluminum, this stop leak is designed to work with it just as well.

Convenient features
For most customers, spending a little more for a stop leak product that delivers a permanent solution is a no brainer. The good news is that with the Blue Devil Radiator & Block Sealer you get the guarantee of a permanent solution plus the effectiveness you would expect from a premium product. There is no requirement to flush your engine before using it. Amazingly, it is compatible with both gasoline and diesel engines making it a decent pick for most car owners.

Verdict
Most users report that they are impressed with how effective this stop leak is. However, there are a couple of complaints about the Blue Devil Radiator & Block Sealer leaving traces of sludge in the system. The simple solution for this is to check the instruction to see whether it is compatible with your system.

Pros
  • Offers a permanent repair solution
  • Easy to sue
  • Compatible with gasoline and diesel engines
  • Comes from a reputable brand
Cons
  • Slightly expensive but worth it
  • Might leave traces of sludge in the system

3. Prestone AS120 Radiator Sealer – 11 oz.

Why we like it: Another stop leak that works just as fast as the previous one we have checked out is the Prestone AS120 Radiator Sealer.

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Design and performance
Thanks to a patented formula that is designed to form a durable and strong mesh around the cracks, this stop leak will help you solve your radiator issues in a matter of minutes. Although it features a capacity to seal leaks as large as 0.016 inches by 0.5 inches, the Prestone AS120 Radiator Sealer can go much further to seal even larger leaks.

Convenient features
The best part about the Prestone AS120 Radiator Sealer is the fact that it works fast and without any interference to the regular flow of your car’s radiator. Apart from the radiator, this stop leak can be used on your water pumps and your heater cores making it convenient for multiple uses. Furthermore, the patented formula contains synthetic components that provide a permanent seal for any large sized hole in your radiator. According to the manufacturer, this stop leak is able to go beyond sealing leaks and deal with corrosive conditions that cause the leaks in the first place.

Verdict
When you are stuck in the highway with a leaking radiator, the last thing you want is a stop leak that is slow to act. But with the Prestone AS120 Radiator Sealer, you can expect speedy results. This is all thanks to the special patented formula. The fact that it works to deal with a corrosive radiator is also a huge plus.

Pros
  • Also deals with corrosion in the radiator
  • Designed for multiple uses
  • Offers a permanent solution
  • Speedy performance
Cons
  • Slightly expensive but worth it

4. AlumAseal ASD Radiator Sealer Tube Dispenser

Why we like it: Whether you choose a liquid or powder stop leak is all a matter of personal convenience. But if you need a quick solution that is easy to use, you might want to check out the AlumAseal ASD Radiator Sealer Tube Dispenser.

Editor’s rating:

Design and performance
This stop leak comes in powder form and offers one of the quickest and easiest solutions to a leaking radiator. With a guarantee that it will not clog your system, the AlumAseal ASD Radiator Sealer is designed for easy compatibility with all antifreeze and coolants. To use it, simply, pour down the powder into your radiator and watch it perform magic in a matter of minutes.

Convenient features
Amazingly, this nifty stop leak can be used in all metal, plastic and tuber radiators making it a decent pick for most car owners. Made in the USA with a high level of quality that is guaranteed to work, the AlumAseal ASD Radiator Sealer Tube Dispenser receives five-star ratings from users thank to its effective formula.

Verdict
Ease of use is one of the top considerations to look out for while picking a stop leak. The AlumAseal ASD Radiator Sealer Tube Dispenser achieves this and more. It is also safe with a design that works with both metal, rubber and plastic radiators which is definitely something to write home about.

Pros
  • Easy to use
  • Works with rubber, metal and plastic radiators
  • Designed not to clog your system
  • Offers a fast solution
Cons
  • It does not provide a permanent fix

5. ATP AT-205 Re-Seal Stops Leaks

Why we like it: A fast-acting stop leak that is used by professionals is what you need if your radiator is showing any signs of a leak. With the ATP AT-205 Re-Seal Stops Leaks you get to enjoy the convenience of a high-quality stop leak that is formulated to blend with oil in the cooling system.

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Design and performance
This stop leak is designed to treat any rubber seals on your radiator and it works with gaskets as well. As long as the leak is not too big, this stop leak will get you ready to get back on the road within 5 hours. It comes in an 8oz bottle that is easy to apply and even if you are not sure about how to go about it, there are straightforward instructions included in the package.

Convenient features
What stands out about the ATP AT-205 Re-Seal Stops Leaks is the fact that it is designed with a formula that strengthens the rubber parts of your radiator. In fact, you can pretty much use it on any part of your car. It is compatible with power steering fluids and it does not contain any petroleum distillates which cause damage to your engine.

Verdict
Although the ATP AT-205 Re-Seal Stops Leaks is lauded for its performance on rubber, it has a couple of downsides that you should pay attention to. First, it does not work with brakes and it is only useful for re-sealing the rubber parts of your radiator. Apart from that, it acts fast to stop leaks and its easy compatibility makes it a favorite for some users.

Pros
  • Relatively fast performance
  • Ideal for sealing old rubber parts
  • Compatible with automotive oils
Cons
  • Only offers rubber seals
  • Complains about damage to the transmission

6. Bar’s Leaks Liquid Aluminum Stop Leak

Why we like it: If you a looking for a radiator stop leak from a reputable brand with results to show, then you might want to settle for the Bar’s Leaks Liquid Aluminum Stop Leak

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Design and performance
This stop leak is designed to be good for your radiator as well as your heater core. It offers a decent repair to your gaskets and by lowering the water temperature; this stop leak can be added directly to your cooling system without the need of flushing afterward. If you think that is amazing, wait till you hear this. The Bar’s Leaks Liquid Aluminum Stop Leak will seal your leaks in just 20 minutes. That’s right, this stop leak is able to perform that fast thanks to the liquid aluminum and the Xtreme cool formula embedded into the liquid.

Convenient features
Bar’s Leaks is pushing the boundaries when it comes to manufacturing next generation stop leaks. With the Bar’s Leaks Liquid Aluminum Stop Leak, you can be sure that you are settling for nothing short of the best in the industry. This stop leak goes beyond sealing leaks to condition your cooling system so that future leaks are prevented before they happen. With a capacity to seal leaks in just 20 minutes, the Bar’s Leaks Liquid Aluminum Stop Leak is by far the fastest performers on our list.

Verdict
For those looking for a reliable future proof solution to a leaking radiator or an overheated engine, the Bar’s Leaks Liquid Aluminum Stop Leak offers one of the best options you can find. It comes with fast performance, and it’s designed to work with all kinds of coolants. On top of everything, it comes from a reputable brand with a proven track record of quality products.

Pros
  • Ideal for repair of large leaks
  • Compatible with liquid glass formula and anti-freeze
  • Fast performance
  • Works with all types of coolants
  • Inexpensive
Cons
  • Only comes in a pack of 1 bottle

7. Zerex Super Radiator Sealer

Why we like it: If you are looking for a quick fix, nothing beats the convenience you can receive from the Zerex Super Radiator Sealer.

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Design and performance
It comes in a 14.5-ounce bottle with the option of getting a case of 12 bottles. With proof of safe usage for multiple applications, the Zerex Super Radiator Sealer is a reliable product to have when your radiator starts to leak in the middle of nowhere. The manufacturer claims that it is the only product Cummins has authorized for professional repairs.

Convenient features
The water-based formula that comes with this stop leak is designed to work with all natural material making the Zerex Super Radiator Sealer a compatible stop leak that can work with many types of radiators. With a claim to a speedy performance that seals holes within one hour, the Zerex Super Radiator Sealer is among one of the fastest performers on our list.

Verdict
Zerex is a little known brand in the world of manufacturing stop leaks. However, that does not mean you should dismiss its Zerex Super Radiator Sealer. Most users give this stop leak raving 5-star reviews for its excellent performance. There are however a couple of complaints from customers who were unimpressed.

Pros
  • Effective performance
  • Easily compatible with various radiators
  • Safe to use on multiple applications
Cons
  • Some users complain of a clogged heater core

8. J-B Weld 2120 Radiator and Plastic Repair Kit

Why we like it: The radiator is an important part of your car and when it stops working due to leaks, having a product such as the J-B Weld 2120 Radiator and Plastic Repair Kit can save you money and time.

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Design and performance
The J-B Weld 2120 Radiator and Plastic Repair Kit is a go-to solution for professional mechanics as well as DIYers. That is because it comes with a pack of 2 radiator and plastic repair stop leaks, a state of the art formula, and a straightforward set of instruction. It is designed to work with fluid tanks, water tanks as well as storage tanks making it a versatile solution for various applications.

Convenient features
When it comes to convenience, the J-B Weld 2120 Radiator and Plastic Repair Kit boasts of a capacity for delivering a permanent repair to your leaking radiator. The deal breaker here is that even though it can be used for multiple applications, this stop leak will not work for aluminum radiators.

Verdict
When it’s all said and done, the J-B Weld 2120 Radiator and Plastic Repair Kit does a decent job of providing a viable solution for those looking for a speedy solution to a leaking radiator. However, this stop leak will is not the best for repairing multiple cracks on a radiator. Plus if you use it in warm temperatures it might not work as expected.

Pros
  • Offers a fast fix
  • Easy to use
  • Includes a double kit package
  • Can be used for various applications
Cons
  • It’s not compatible with all radiators
  • Cannot be used in places with warm temperatures

9. Irontite All Weather Seal

Why we like it: Another brand in the coolant additive industry that we just had to mention on our list is Irontite. Their Irontite All Weather Seal is one of the best stop leaks you can find if you need a reliable solution for all conditions.

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Design and performance
Irontite All Weather Seal comes with a design that is easy to use. All you have to do is pour it into your coolant mixture and you will be ready to get back on the road. It works with both gas and diesel engines making it a must-have for most car owners. Plus, the formula used to manufacture the Irontite All Weather Seal stays dissolved to prevent chances of a clog in the system.

Convenient features
Basically, when you need a high-quality stop leak that is backed by a reputable brand, the Irontite All Weather Seal is by far one of the best solutions out there. It comes with a capacity to remain effective no matter the weather condition making it a must-have stop leak for facing the elements.

Verdict
The Irontite All Weather Seal is a favorite among professionals and for a good reason. It works easily with multiple types of cooling systems and it’s also compatible with gas, diesel and propane engines which is great. Although it sits slightly on the pricey side, the convenience of the features it offers make it a worthwhile deal.

Pros
  • Feature the convenience of an all-weather design
  • Compatible with diesel and gasoline engines
  • Mixes well with anti-freeze
Cons
  • Slightly expensive but worth it

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

Why we like it: Lastly, we have the J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak. This stop leak is one of the best stop leaks for those who need a stop leak solution that can also act as a lubricant to the components of your radiator.

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Design and performance
It comes with a design that is ideal for DIYers who need a solution that is gentle yet tough on cracks and leaks. Designed as a powder stop leak, the J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak features a non-toxic compound that easily flows and mixes in every part of the cooling system thanks to the finely ground particles inside. Basically, this stop leak is an inexpensive solution that will not only save you money but also time.

Convenient features
Some of the outstanding features of this stop leak include its capacity for delivering a fast fix to your leaks. In fact, this powder solution will go beyond sealing leaks to act as a rust inhibitor as well as a lubricant. If buyer reviews are anything to go by, the J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak is also ideal for a long lasting fix to your cooling system.

Verdict
The last thing you need after signs of a leak to your radiator is a stop leak that puts your engine at the risk of getting clogged. Well, if you go with the J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak, you can put those fears aside since it comes with the guarantee that it will not clog or harm your cooling system. It’s also one of the most inexpensive stop leaks we have featured here making it a contender for those looking for convenience.

Pros
  • Versatile performance on different products
  • Easy to use
  • Inexpensive
  • Strong and durable fix
  • Nontoxic compound
  • Offers a quick fix
  • It can also be used as a lubricant
Cons
  • Might not be compatible with all cooling systems
  • The fix is not permanent

Guide to Buying the Best Radiator Stop Leaks

What is a radiator stop leak?
A radiator stop leak is a product that you can use to seal the leaks on your car’s radiator. Normally, a car radiator tends to wear and tears with time leading to the development of leaks. There are only two options for you to solve a leaking radiator. You can either choose to buy a new radiator as a replacement for your old one, or you can get a radiator stop leak that protects your radiator preventing further damage. The cheaper option is to use a radiator stop leak. Most radiator stop leaks come either in a liquid, powder or tablet form.

Also, radiator stop leaks vary in the way you use them. While some work by being poured directly into the cooling system, others will require you to conduct a system flush before and after application.

Most brands will claim that their product provides a 100 percent solution. Sure a high-quality radiator stop leak can do a pretty good job but if the problem in your radiator is inherent, you can be sure to have the leak problem pop up somewhere in the future.

How do stop leaks actually work?
The way stop leaks works is really simple. The ground up almond shells or filler ceramic particles circulate through the radiator’s cooling system when you pour it inside. Then, while the cooling system is under pressure these particles circulate around the leak and the pressure forces them to plug the gap, therefore, sealing the leak.

Rarely do filler sealers form a permanent seal. With that in mind, you might need to flush the coolant and add a new one every once in a while. Technological advancements have brought about micro-sphere nanotechnology that features very small fibers that work just like other filler products. The difference is that with these types of radiator stop leaks, the tiny fibers build a mesh that hardens and cures the engine heat. This provides more of a permanent seal that continues to work even after you flush the system.

For radiator stop leaks made with sodium silicate, the particles in the liquid melt to form a plug. Since Sodium silicate melts at 212 to about 2210 F, it melts and re-melts as temperature rises then forms a permanent seal once the radiator cools down. That is why some of the best radiator stop leaks are made with sodium silicate mixed with other metallic filler material.

What causes leaks in my radiator, heater core or steel tubing?
One of the major causes of leaks is owner neglect. You are required to change your radiator’s coolant according to manufacturer recommendation regularly. When you neglect this, the system starts to corrode from the inside out. In fact, in most cases, the pinhole leak in the system is usually a symptom of a much larger problem that cannot be presently solved by a stop leak product. Although most radiator stop leaks only provide a temporary solution, if you apply the stop leaks at the very first sign of a leak, you might end up with a better outcome. Seriously, do not wait until you get a major leak to start applying your stop leak. With that in mind, it is better to be preventive beforehand by making sure you change your car’s coolant every once in a while.

How much does it cost to repair my radiator hose?
Well, the actual cost of leaking repairing a radiator varies from shop to shop. Besides, your car might need extra maintenance that the mechanics will add to your bill raising the cost much higher. The only alternative to taking your car to a repair shop is to do it yourself. Here, the only cost you will incur is the cost of the repair kit which might be about $45 to$100. You can also look around different garages and ask for estimated to get the best deal.

In this guide, we show you how to pick a radiator stop leak that works for your car. These considerations will help you save money and time while looking for the best radiator stop leak

  • Different forms of Radiator stop leaks: Radiator stop leaks come in liquid, tablet and powder form. In terms of effectiveness, there is no particular form of radiator stop leak that is better than the other. What you settle for is based on your personal preferences and conveniences. With liquid radiator stop leaks, you will find them in plastic bottles and in a variety of amounts. This type of stop leak works with a couple of particles that do the work of sealing the leaks. Tablet stop leaks are designed to be dissolved in warm water before they can be poured into your radiator. Powder stop leaks come in all sorts of packaging but work similarly to liquid stop leaks.
  • Consider the chemical composition of the stop leak: You need to check the composition of your stop leak and make sure it only contains safe chemicals for your engine. If the chemicals are not compatible with your engine make, serious damage to your engine or other anti-freeze problems could be the outcome.
  • Check to avoid clogging: While some stop leaks will work well with your car’s engine some stop leaks will actually cause some clogging in the system. This is why it is important to check whether the product you pick is healthy for your car’s radiator.
  • Measure effectiveness: after you are done applying the stop leak, you need to confirm if the product is effective. While some products offer a quick solution that works in a matter of minutes some are completely ineffective. Beyond checking for the obvious signs of an overheated engine and puddles under your car, you need to also look at what other users are saying about the product.
How to use a radiator stop leak
If you are worried about one day being stranded along the highway with a major leak in your radiator, you need to learn how to use a radiator stop leak. Actually, the learning curve is anything but steep. The idea behind a radiator sealant or a radiator stop leak is to introduce a chemical that will circulate around those leaks and seal them. Although in most cases a radiator sealant cannot provide a permanent solution, using a radiator sealant can help you run with your car long enough to get to a repair shop.

Here is a step by step guide on how to go about it:

  • Confirm the size of the leak: The very first sign of a leaking radiator is an overheated engine that often forms a puddle under the car. You can confirm that you have a leak by opening the radiator cap and checking to confirm if there is anything unusual about the level of the coolant. Make sure you let the engine cool down before opening the radiator to carry out the visual inspection.
  • Buy a reliable radiator stop leak: With a variety of products available, solving the problem to your leaking radiator starts with the product you choose. Therefore go with a formula that is tested and proven to work. It helps to go with a recognized brand that is known for helping alleviate leaks in radiators.
  • Read the instruction: Different manufacturers use different chemicals to manufacture stop leak products. Therefore it is important that you read through the instruction to take note of any steps that you need to follow in order to have the radiator stop leak work.
  • Pour the stop leak into the radiator: At this point, make sure you follow the instructions so that you stick to the recommended amount. In most cases, the recommended amount will be a full bottle of the stop leak. Be careful not to drain out any coolant.
  • Coolant and radiator fluid: now add radiator fluid through the radiator cap until it levels up to the coolant amount according to the recommendations of the manufacturer.
  • Now start the car: After you have added the radiator fluid, warm up the engine to allow for the circulation of the plastic sealant. This will enable the stop leak to seal up the cracks in the radiator as well. You can also run the car for about 10 minutes to make sure the process is thoroughly complete.
  • Fill the radiator with water: at this point, you need to fill the radiator with a mixture containing 50 percent water and 50 percent coolant. This mixture is useful for cooling the system. After this, you can let your car sit for about 12 hours before driving it as usual.
  • Confirm your results: any signs of a puddle underneath your car or an overheated engine means there are more leaks to take care of. In case the first application did not work, you will have to take your car to a professional to get it properly fixed. Stubborn leaks on your radiator are usually a symptom of a much bigger problem.

Final Words

So there you have it, folks. With our list of the 10 best radiator stop leaks, you will surely find a stop leak that works for your needs. If you are looking for a premium quality stop leak, we recommend going with the K-Seal ST5501 Multi Purpose One Step Permanent Coolant Leak Repair. This stop leak boasts of many positive reviews from happy customers plus it comes from a reputable brand.