Car Care

The 10 Best Radiator Stop Leaks of 2020

Best Radiator Stop Leak

Photo: K-Seal

The radiator is a very important part of any car because the engine would overheat and get damaged without it. This makes it necessary to always keep an eye on your radiator and to stop any leaks once you become aware of them. 

Of course, the best solution is to find a mechanic immediately, who will take care of the leak, but if you're in a hurry or in the middle of nowhere, then you need to have the best radiator stop leak.

In this piece, we provide a list of some of the best options in the market, as well as all the information you need to use them, and also a guide on how to choose between these different radiator stop leak options.

10 Best Radiator Stop Leaks – Review

IMAGE

PRODUCT

​FEATURES

Bar's Leaks 1186 Liquid Aluminum Stop Leak

1. Bar's Leaks 1186 (Best Overall)

  • High-quality top brand product
  • Seals and conditions radiator system
  • Water temperature lowering technology
  • Works with most anti-freeze
K-Seal ST5501 Permanent Radiator Stop Leak

2. K-Seal ST5501 (Best Value for Money)

  • Great value for money
  • Repairs radiator permanently
  • Easy pour and go use
  • Mixes with any antifreeze 
Dike Temporary Radiator Stop Leak

3. Dike Stop Leak (Fastest Acting Resealer)

  • Super-fast sealing
  • Compatible with any antifreeze
  • Improves gasket sealing ability
  • Does not block small coolant system passages
ATP AT-205 8-Oz Re-Seal Bottle

4. ATP AT-205 (Effective Rubber Seals Repair)

  • Permanently seals all gaskets & rubber seals
  • Compatible with all types of oils
  • No petroleum distillates
  • Concentrated and economical solution
Bar's Leaks Radiator Stop Leak Tablets

5. Bar's Leaks HDC (Professional Strength Formulation)

  • Delivers professional-quality sealing strength
  • Easy to use and store tablets
  • Conditions cooling system and prevents rust
  • Effective electrolysis control
  • More budget friendly
J-B Weld Perm-O-Seal Radiator Stop Leak

6. J-B Weld DS-114 (Easy Mix Stop Leak Powder)

  • Quick and easy mix and flow
  • Does not harm, clog or obstruct system
  • Permanent fix
  • Acts as rust inhibitor and lubricant
Bar's Leaks 1109 Liquid Copper Radiator Stop Leak

7. Bar's Leaks 1109 (Unbeatable Copper Radiator Stop Leak)

  • Potent liquid copper formula
  • Simple and easy use
  • Anti-freeze compatible
  • Does not clog or obstruct
InterDynamics 375CS

8. InterDynamics 375CS (Safe and Versatile)

  • Versatile for different functions
  • Safe on all vehicle makes/models
  • Works with any antifreeze
  • Professional-grade formula
Alumaseal Radiator Stop Leak Powder

9. Alumaseal ASBPI12 (Simple but Efficient)

  • Safe, quick and easy leak stop
  • Effective rust prevention
  • Compatible with any antifreeze
  • Does not clog cooling system
Prestone AS145 Radiator Stop Leak

10. Prestone AS145 (Unique Natural and Synthetic Components Formula)

  • Effective natural and synthetic fibrous
  • Seals holes up to 0.5 inches large
  • Stops and prevents corrosion
  • Will not interfere with flow

PRODUCT

1. Bar's Leaks 1186

(Best Overall)

Bar's Leaks 1186 Liquid Aluminum Stop Leak
  • High-quality top brand product
  • Seals and conditions radiator system
  • Water temperature lowering technology
  • Works with most anti-freeze

2. K-Seal ST5501

(Best Value for Money)

K-Seal ST5501 Permanent Radiator Stop Leak
  • Great value for money
  • Repairs radiator permanently
  • Easy pour and go use
  • Mixes with any antifreeze 

3. Dike Stop Leak

(Fastest Acting Resealer)

Dike Temporary Radiator Stop Leak
  • Super-fast sealing
  • Compatible with any antifreeze
  • Improves gasket sealing ability
  • Does not block small coolant system passages

4. ATP AT-205

(Effective Rubber Seals Repair)

ATP AT-205 8-Oz Re-Seal Bottle
  • Permanently seals all gaskets & rubber seals
  • Compatible with all types of oils
  • No petroleum distillates
  • Concentrated and economical solution

5. Bar's Leaks HDC

(Professional Strength Formulation)

Bar's Leaks Radiator Stop Leak Tablets
  • Delivers professional-quality sealing strength
  • Easy to use and store tablets
  • Conditions cooling system and prevents rust
  • Effective electrolysis control
  • More budget friendly

6. J-B Weld DS-114

(Easy Mix Stop Leak Powder)

J-B Weld Perm-O-Seal Radiator Stop Leak
  • Quick and easy mix and flow
  • Does not harm, clog or obstruct system
  • Permanent fix
  • Acts as rust inhibitor and lubricant

7. Bar's Leaks 1109

(Unbeatable Copper Radiator Stop Leak)

Bar's Leaks 1109 Liquid Copper Radiator Stop Leak
  • Potent liquid copper formula
  • Simple and easy use
  • Anti-freeze compatible
  • Does not clog or obstruct

8. InterDynamics 375CS

(Safe and Versatile)

InterDynamics 375CS
  • Versatile for different functions
  • Safe on all vehicle makes/models
  • Works with any antifreeze
  • Professional-grade formula

9. Alumaseal ASBPI12

(Simple but Efficient)

Alumaseal Radiator Stop Leak Powder
  • Safe, quick and easy leak stop
  • Effective rust prevention
  • Compatible with any antifreeze
  • Does not clog cooling system

10. Prestone AS145

(Unique Natural and Synthetic Components Formula)

Prestone AS145 Radiator Stop Leak
  • Effective natural and synthetic fibrous
  • Seals holes up to 0.5 inches large
  • Stops and prevents corrosion
  • Will not interfere with flow

1. Bar's Leaks 1186 – Best Overall

Bar's Leaks 1186 Liquid Aluminum Stop Leak

Photo: Bar's Leaks

With about 70 years of experience in the industry, Bar's Leaks is one of the best coolant stop leak brands that you'll find when it comes to radiators and stop leak solutions for plugging their leaks. Hence, their model 1186 does not make the top of our list by chance.

This particular offer uses liquid aluminum, which not only seals your radiator's leaks but also conditions the system. It has a compound named Xtreme Cool as well, which is a formula to drastically reduce the car's water temperature and avoid overheating in the process.

These two formulas combine to produce fast results in as little as 10 minutes, working on aluminum, plastic, and other types of metals. It's also the best plastic radiator stop leak on this list.

It's also formulated to work with most types of anti-freeze, so there's no need to flush your radiator first before use. You can use it as well for gaskets, heater cores, and freeze plugs sealing.

This stop leak doe not seem effective at fixing big leaks, but this is not a unique problem as you will hardy find similar product that can be effective on larger radiator leaks.

Pros:

  • Great product from a great stop leak brand
  • Seals radiator, gasket and heater core leaks
  • Additionally lowers water temperature
  • Minimal risk of clogging your radiator
  • Can work with most antifreeze

Cons:

  • It won't fix big leaks in your radiator

2. K-Seal ST5501 – Best Value for Money

K-Seal ST5501 Permanent Radiator Stop Leak

Photo: K-Seal

The K-Seal ST5501 offers to permanently plug the hole in your cooling system for the lifetime of the engine. Given that you will not need to buy more of it for a long time and its more affordable price tag, it will give you great value for money.

It will also work on head gasket leaks, water pump leaks, and heater core leaks. There are no known issues with anti-freeze formulas, and it will work with most of them, which eliminates the need for draining or flushing. 

Using this radiator stop leaks is also quite straightforward as you will only need to shake it, pour into the radiator and run the engine to circulate it.

Although this product seems to have strong clogging potential given its potent sealing capability, if you follow the manufacture instructions for using it, you will never have to worry about clogs.

Pros:

  • Good value for cash
  • Permanent leak repair
  • Mixes and works well with all anti-freeze formulas
  • Works on various other parts besides radiator
  • Straightforward to use

Cons:

  • Strong clogging potential

3. Dike Stop Leak – Fastest Acting Resealer

Dike Temporary Radiator Stop Leak

Photo: Conklin Dike Temporary Radiator Stop Leak

Dike is also one of the best radiator stop leaks and is perfect product to have in your car's emergency kit for fast on the spot repairs. It has been formulated to stop the radiator leak in seconds to ensure almost zero vehicle downtime.

You can also use it as a preventive measure on any system that's working under severe conditions. And this is because it is also useful for improving the gasket's sealing capability. 

This stop leak is compatible with all kinds of radiator coolants, including the green and orange types. Better yet, it will work on any radiator cooling system, including cars, trucks, and tractors.

Dike recommends 1 pint for every 4 gallons of your car's radiator capacity, and this means four ounces for each gallon. Hence, with this ration it means a little of it goes a long way.

This Dike radiator leak stop will also not block any small passages in the coolant system, which means it only seals without affecting the effectiveness of the radiator.

Although this is a temporary solution and the name also suggests that, this is not a big drawback as most of these products are all short term solutions.

Pros:

  • Stops radiator leaks very fast
  • Works with all kinds of anti-freeze formulas
  • Absolutely no risk of clogging your cooling system
  • Improves the sealing efficiency of gaskets
  • Can also work as a preventive measure

Cons:

  • Only works temporarily

4. ATP AT-205 – Effective Rubber Seals Repair

ATP AT-205 8-Oz Re-Seal Bottle

Photo: ATP Automotive

It could happen that you're experiencing a rubber leak, maybe from a part of your radiator or from any other part of your car engine that uses rubber seals.

What you would need is the ATP AT-205 formula and your rubber engine parts will get reconditioned and re-sealed in a matter of hours. Simply empty the right amount into wherever you need it and that's it.

It's compatible with most oils used in different car parts and works well in the power steering system, the engine, transmission e.t.c.

The working principle of this ATP Re-Seal is that it's a plasticizer, which is a type of chemical that gets used in rubber manufacturing to keep it strong and flexible, and this is what it'll do to all old rubber parts it touches in your car.

Also, the formulation is more concentrated to make it highly economical as a little of it goes a long way. There are no petroleum distillates in the formula and stop leak seal without causing any over-swelling or breaking down the seals.

Although this stop leak might only be effective on gaskets and rubber seals, you will hardly ever need to use it for any other kind of seal, and so this should not be a big concern

Pros:

  • Re-seals all rubber seals in any part of your car
  • Fast acting to stop leaks fast
  • Compatible with a range of automotive oils
  • More concentrated and economical
  • Contains no distillates

Cons:

  • Only revives rubber seals

5. Bar's Leaks HDC – Professional Strength Formulation

Bar's Leaks Radiator Stop Leak Tablets

Photo: Bar's Leaks

With this Bar's Leaks radiator stop leak tablets, you get to always have a professional-quality solution to your leaky radiator's with you, but in an easy to use and store tablet form.

Besides sealing the leaks, the potent formulation of the tablets also makes them ideal for conditioning the cooling system, and will also help prevent rust and corrosion.

Also, these tablets offer effective electrolysis control, and there is nothing much to do when it comes to using them. To use them, simply dissolve the required amount in warm water and then pour the solution into your radiator.

And to make these tablets an even better buy, they are the cheapest option on our radiator stop leak reviews.

For large leaks, these tablets are not very effective, but in many instances, there is nothing much that a radiator stop leak can do when dealing with massive holes. Hence, this is not a unique issue for this particular option.

Pros:

  • Potent professional-grade formula
  • Super easy to use
  • Effective on electrolysis control
  • Additionally, conditions the cooling system and inhibits corrosion
  • Offered at a very low price

Cons:

  • Won't plug large leaks

6. J-B Weld DS-114 – Easy Mix Stop Leak Powder

J-B Weld Perm-O-Seal Radiator Stop Leak

Photo: J-B Weld

How about some powder? You know, the best cooling system stop leak doesn't need to be in a liquid or tablet form, it just has to work well and keep your car safe.

This J-B Weld Perm-O-Seal is the first powdered product on this list, and it also comes at a good price. The Perm-O-Seal is a non-toxic compound, specially formulated and ground to a fine particle size, so it can mix easily.

Besides sealing the cooling system , this stop leak will not cause any harm, obstruction and clogging, which makes it safe to use on any vehicle.

Also, it is very effective at preventing rust and acts as a water lubricant to improve the overall effectiveness of the cooling system.

The fast and permanent fixing capability also helps make this one of the best coolant stop leak as it is very handy when you need a permanent solution.

While it is true there are many cheaper stop leak powders out there, few are as effective as this ones, and so it is worth the extra buck or two.

Pros:

  • Specially formulated for easy mixing
  • Additionally, lubricates system and inhibits corrosion
  • Offers a permanent repair of your radiator
  • Does not clog the system

Cons:

  • There are cheaper powder formulas available

7. Bar's Leaks 1109 – Unbeatable Copper Radiator Stop Leak

Bar's Leaks 1109 Liquid Copper Radiator Stop Leak

Photo: Bar's Leaks

Bar's Leaks top-rated radiator stop leak repairs larger leaks in your radiator, gasket, heater core, and the like. Designed for copper radiators, this stop leak provides you with a temporary but excellent seal.

As with other Bar's Leaks products, usage is simple and easy. Just empty the right amount into your radiator or affected part, and that's it, no need to flush it later. One bottle is enough for most engines ranging from 4 to 8 cylinders.

Its liquid glass formula is anti-freeze compatible and you're guaranteed to see results within 20-30 minutes of application.

This Bar's Leaks 1109 is also guaranteed not to clog your system, coming from a company with over 70 years experience in the radiator stop leak industry. It's a top choice for those looking for the best heater core stop leak formula.

While this stop leak might not offer a permanent fix, it will keep the radiator and other components sealed for up to 5,000 miles, which is still quite impressive.

Pros:

  • Works well fro copper radiators
  • Seals radiator, heater core, head gaskets e.t.c
  • Straightforward to use
  • Compatible with most antifreeze
  • Will not cause any clogging or obstruction

Cons:

  • It's only a short-term fix

8. InterDynamics 375CS – Safe and Versatile

InterDynamics 375CS

Photo: InterDynamics

The versatile functionality of the InterDynamics 375CS is what makes it stand out and sets it apart from others out there. This product can work as a radiator coolant, leak stop and is also very useful at detecting the leaks in your coolant system.

Its professional-grade formula not only makes it highly potent, but also allows you to use it safely with almost any vehicle type or model on the road today.

Also, using it will be more convenient and easy as you will not need to do any draining or flushing as it is formulated to be compatible with any antifreeze.

The small bottle contains less product when compared to others on our list. But, with this stop leak, a little of it goes a long way, as it is highly concentrated. And so this should not be a deal breaker.

Pros:

  • Works as leak stop, coolant and leak detector
  • Idel for use on any vehicle type
  • Compatible with all antifreeze
  • Special professional-grade formula

Cons:

  • Little product in bottle

9. Alumaseal ASBPI12 – Simple but Efficient

Alumaseal Radiator Stop Leak Powder

Photo: Alumaseal

With this radiator stop leak from Alumaseal, you get a product that's so simple, it's only allowed as an add-on item to other orders. But, despite its simplicity, is still highly efficient and effective.

It's safe on all kinds of materials from plastic to metal and rubber. It's also guaranteed to work with all coolants and anti-freeze additives in your cooling system.

Also, the formula is effective at preventing rust to ensure your cooling system stays in great shape for long, and it will not clog or obstruct the cooling system.

Using it is easy, just pour the powder into the radiator, making sure it's cool before you remove the cap. Then close the cap and run the engine for some minutes. Each pack will work on radiator coolants up to 22 quarts in volume.

If you only want to try out this stop leak, finding just a single strip can be hectic given hat it is mostly provided as an add-on. However, you can still buy a pack of 12 without spending much.

Pros:

  • Easily stops leaks in your system
  • Safe for all your car's metal, plastic and rubber parts
  • Guaranteed to not clog your cooling system
  • One packet can treat up to a 22-quart system

Cons:

  • A single card is only allowed as an add-on item

10. Prestone AS145 – Unique Natural and Synthetic Components Formula

Prestone AS145 Radiator Stop Leak

Photo: Prestone

The Prestone AS145 features a patented formula that makes it outstanding. It comes with a mix of natural and synthetic fibrous particles, which flow freely with the coolants and deliver their sealing capability wherever needed.

This enables this formula to seal leaks up to 0.02 inch by 0.5 inch in size, all thanks to the outstanding features of its fibers.

You also get corrosion inhibition. Since corrosion is usually the culprit that leads to leaks in the first place, this product is very useful for preventing future leaks. And it will do all this without affecting the flow in the heater core or radiator.

On the other hand, Prestone offers no guarantee that these fibers won't clog your cooling system. But, provided you follow the directions, there is less likelihood  of clogging.

Pros:

  • Includes natural and synthetic fibrous particles
  • Can seal leaks up to 0.02 x 0.5 inches
  • Also includes corrosion inhibitors to cut corrosion

Cons:

  • Not completely clog-free

How to Buy the Best Radiator Stop Leaks

How to Buy the Best Radiator Stop Leak

Photo: Prestone

If you are not sure the best radiator stop leak to buy, here is a list of the important factors to watch out for.

1. The Different Types

Radiator stop leaks are available in three different forms. They are liquid, powder, and tablet forms. No single form is better than the other, in fact, choosing one type over the rest is merely about personal preference and convenience.

  • Liquid. You'll find this type in plastic cans of all sizes. The liquid stop leak like Prestone AS145 is usually mixed with the necessary particles, which are held in liquid form.
  • Powder. Powdered stop leaks such as J-B Weld DS-114 come in different packaging. All you have to do is open the packaging and empty its content into your car's radiator.
  • Tablet. These are the same as the others, except that you can either dissolve them in your anti-freeze or in warm water first before pouring it into your radiator to get to work. A good example of these stop leaks is the Bar’s Leaks HDC.

2. Clog Prevention

All radiator stop leaks are not built the same, some will tend to clog, while others will work more freely.

You have to check to make sure that the particular product in question works well with your car's radiator type or heater core.

No matter how potent and effective a stop leak might be it will not be very useful fro you if it causes clogging as this means you will have more problems to deal with.

3. Compatibility and Additives 

Different leak stops contain different compounds depending on the manufacturer. You will need to check its composition to make sure it doesn't contain any chemicals that could cause problems for your vehicle, and it is also compatible with your cooing system.

For the additives, you should go for those that contain compounds that offer effective sealing such as the natural and synthetic fibers on the Prestone AS145.

Something that will contain compounds that are effective at preventing rust and corrosion like Bar’s Leaks HDC will also be perfect.

Also, it is important to make sure that the product is compatible with the antifreeze that you use on your vehicle. But, here those that are formulated to work with any antifreeze are more preferable.

4. Effectiveness

For the simple fact that a radiator stop leak has the single job of stopping radiator leaks, measuring the effectiveness of a radiator stop leak is, therefore, a simple and straightforward affair.

All you need to find out is whether the leak was effectively plugged or not and how long it took for the particular product to plug the leak.

Asking around or reading customer reviews is a great way to confirm how effective a particular brand of radiator stop leak is for your kind of car.

How to Use a Radiator Stop Leak

How to Use a Radiator Stop Leak

Photo: knowhow.napaonline.com

Here are the step to follow when using a radiator stop leak.

Step 1. Confirm a Leak

The first thing you need to do here is, of course, to confirm that you've got a leak. The first signs of a radiator leak include an overheating engine and a puddle under the car.

To confirm that you've got a leak though, you'll need to open the radiator's cap and look inside to confirm an abnormally low level of the coolant.

If the engine was running, then let it cool down because you don't want to open a hot radiator. After the engine has cooled for a while, open it and carry out a visual inspection of your car's radiator.

Step 2. Read the Instructions

Once you've confirmed a leak and you've also located your radiator stop leak, the next step is to read its manufacturer's instructions.

This is necessary because there could be things to note or a particular process to follow. Radiator stop leaks come in different forms and get made using different chemicals, so you don't want to make any mistakes.

Step 3. Dispense the Stop Leak

Now is the time to remove the radiator's cap, if it's not already open and to empty the product into your radiator. Make sure to follow any instructions and to leave the engine off at this stage.

If you've lost a lot of coolant fluid, then you might want to fill up the radiator again, but only after you've emptied the stop leak product.

Step 4. Start the Engine

This is necessary so that the coolant can circulate the product and let it do its work. For some radiator stop leaks, the results are almost instant but for most it will take anywhere from 10 to 30 minutes.

Step 5. Check the Leak Again

You'll need to let the engine run for a while or drive the car and then carry out another visual inspection. The signs to check are the engine temperature and any puddles underneath the car.

Step 6. Find a Professional

Using a radiator stop leak is generally a temporary solution to your car's radiator problem. You should, therefore, schedule a meeting as soon as possible with your mechanic to get it properly fixed. Some manufacturers though, offer permanent radiator stop leaks, so it's left for you to choose what you want.

FAQs

Q: Does Radiator Stop Leak Really Work?

A: Yes, they will work as the formula contains components that are effective at patching up leaks in your radiator. But, in most instances they are only effective on small holes.

Q: Will Radiator Stop Leak Harm My Engine?

A: No, provided you use it properly and in the right volume, it will not harm your engine. In fact, most are formulated to help improve the vehicle's overall performance. They can also be used to seal leaks on other vehicle parts like freeze plug and heater core besides the radiator.

Q: Can Radiator Stop Leak Cause Overheating?

A: It depends. If the product that you use is good quality, it will not cause any clogging and hence ensuring a proper flow is maintained, which minimizes the likelihood of overheating. But, cheap, inferior quality product can cause clogging and lead to overheating.

Q: Do I Need to Drain My Cooling System after Using Radiator Stop Leak?

A: No, most radiator stop leaks will not require any draining after use. Also, most are compatible with any antifreeze, and so no draining or flushing is needed before use.

Q: How long Does Stop Leak Last in a Radiator?

A: This will depend on the formulation and quality of the product and also on the size of the leak you have. For a high-quality product, the stop leak should stay in the radiator for at least 10,000 miles if you are dealing wit small leaks.

Conclusion

The final radiator stop leak choice is yours alone to make because choosing between the convenience and price of powders and tablets, versus the highly effective liquid formulas, is a different experience for each person.

With that in mind, the Bar's Leaks 1186 is our best overall product because besides being highly effective at sealing leaks, it is also a high-quality top brand product that also helps lower water temperature.

However, by permanently repairing the leaks and with its easy pour design, the K-Seal ST5501 will give you the best value for your cash.

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