The 10 Best Radiator Stop Leak On The Market 2023

The roles that radiators play in the typical car are too critical to be overlooked.

The radiator is the device that cools the engines of cars. It consists of thin tubes which circulate the coolant in the engine.

Just like every other part of the car, the radiator also sustains leaks from time to time. These leaks are not at all healthy to the engines.

This is why you have to mitigate them appropriately.

10 Best Radiator Stop Leak Reviews

1: ATP AT-205 Re-Seal Stops Leaks

 ATP AT-205 Re-Seal Stops Leaks

Ordinary saloon cars are quite prone to leaks owing to their constant motions. However, their leaks are never that much critical. An ordinary stop leak of this kind is therefore handy and relevant for their use. Do get hold of it for such messes.

Professional Strength

On the whole, the re-sealer exudes fast-acting strength. It takes the shortest duration of time to bring about the desired ends. This stems from its potent formulation that produces awesome sealing power.

Seamless Compatibility

This stop leak is compatible with a vast array of both synthetic and conventional oils. Examples of these include the automatic transmission fluid, power steering fluid, gear oil, and hydraulic oils, among others. The benefit of utmost convenience is thus yours to reap.

Maximum Capacity

Overall, the bottle holds 8 ounces of sealant. This is sufficient to serve a whopping 6 quart of the leak. You will not have to purchase brand new sealants every quite often as it shall last you long. You will also obtain the peace of mind you need to enjoy the benefits for longer.


  • Contains no petroleum distillates,
  • Does not over-swell or break down the seals
  • Stops the leakages very fast
  • Adjusts accordingly in response to the prevailing environment
  • Rejuvenates all rubber seals and gaskets in engines


  • Requires plenty of storage space while not in use
  • Not so safe due to the potent formulation
  • Confers limited use and applicability

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2: Bar’s Leaks 1109 Radiator Stop Leak

Bar’s Leaks 1109

Larger leaks are ordinarily more difficult to stop. This is because they require extremely potent sealants that last long also. Only a specially formulated stop leak of this kind may come to your rescue. Try it for those large leaks and spot a difference.

Anti-freeze Formulation

It does possess an anti-freeze formulation. This basically comes in the form of the sodium silicate liquid glass formula. This formulation spares you the agony of having to drain the cooling system. It also saves you a great deal of time and effort in so doing.

Permanent Outcomes

You should expect to reap the benefits of permanent outcomes from this sealant. This yet again stems from its potent formulation. It can, as a matter of fact, handle a range of other parts of the automobile beside the radiator alone, These are heads, blocks, heater cores, and gaskets, to mention but a few!


With this sealant, you obtain much more than just blocked leak. It also has the liquid copper block seal intake. It can therefore handle and seal larger leaks such as those that are found in trucks and the sporting utility vehicles.


  • Combats larger leaks better than all the other substances of its kind
  • Stops overwhelming leaks faster and promptly
  • Does not harm the cooling system at all
  • Accompanied by a how-to video for further assistance
  • More effective and less expensive than most other seals


  • Potentially harmful to the skin
  • Backed by less generous warranty
  • Not so cost-effective

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3: Bar’s Leaks 1186 Liquid Aluminum Stop Leak

Bar’s Leaks 1186

High-performance cars are sensitive to any fluctuations in the engine capacity. This is why the smooth operations of their engines have to be upheld at all times. A reliable sealant of this kind is what may guarantee this kind of performance.

Engine Conditioner

Apart from sealing the leaks, this sealant can also condition the engine. This simply means that it can keep the engine pressure at constant state throughout the journey. This is what is responsible for the smooth operations of the engine.


This is a heavy-duty synthetic cutting and grinding fluid. It handles aerospace aluminum and other aerospace alloys pretty well. Given that these form a vital part of racing cars, they enhance the operations and speeds of the cars considerably.

Advanced Seal Polymer Additive Package

Lastly, it does have this advanced seal polymer additive package. This operates by furnishing a polymeric film round about the seal. This film helps to prevent excess oil from dodging the seal in the normal engine operations.


  • Seals freeze plug leaks
  • Repairs gasket leaks and heater core leaks
  • Lowers water temperature
  • Suppresses radiator leaks also
  • Prevents the likelihood of future leaks


  • Quite potent and potentially corrosive
  • Takes longer to bring about the desired ends
  • Quite weighty (weighs 1.2 pounds/0.5 kg)

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4: K-Seal ST5501 Multi-purpose Leak Repair

K-Seal ST5501

A good sealant has to be able to do more than just seal leaks. It should be able to fix cracks and perform a number of the radiator related chores. This sealant can do just that. It can handle the various parts of the engine like the cylinder heads, gaskets, and the water pump.

Scientifically Tested

Unlike most other sealants on the market, this one is scientifically tested to conform to the stringent standards. It is subsequently certified to be able to perform well under all operational conditions. This guarantees you the utmost reliability at all times.

Trusted by Professionals

Most professionals world over have developed a sense of trust in this sealant. They have used it time and again and have never been let down at all. This trust guarantees you the same benefits and levels of reliability also.

Higher Cooling Capacity

By virtue of possessing the 8-fluid ounce capacity, this sealant is sufficient enough to handle large-scale sealing tasks or prolonged use. As a matter of fact, it can perform around 20 cycles of cooling sessions. This again confers to you the fringe benefit of topmost performance.


  • Brings about more permanent and long-lasting outcomes
  • Able to mix with all the anti-freeze substances
  • Requires no draining or flushing of the engine
  • Deals effectively with most leaks in water-cooled engines
  • Spans the entire lifetime of an engine


  • Limited capacity (9.6 ounces)
  • Easily over-pressurized
  • May not always reach the affected areas easily

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5: Bar’s Leaks PLT11 Pelletized Radiator Stop Leak

Bar’s Leaks PLT11

Unlike most other stop leaks on the market, this one comes in the form of a pellet rather than fluids. Pellets are better in that they can be transported easily. They are also less susceptible to spills and possible damages to the skin and interior of the vehicle.

Great for Larger Leaks

Perhaps no other sealant is as great for larger leaks as this one. Its pelletized form allows it to fit into larger holes and seal them sharply. You will find it particularly useful for the heavy commercial vehicles like trucks and trailers.

Water Pump Lube

It can also play the role of lubrication besides sealing leaks. This stems from its possession of the water pump lube. This is not to mention that it can also suppress the proliferation of rust and scales. It thus returns greater value for money.

Easy-to-use Powder Formula

Both the skilled and the novice mechanic shall find the sealant easier to apply. The sealant indeed has an easy-to-use powder formula. As such, you will not have to possess great technical skill and expertise to comprehend and/or engage it at all.


  • Seals leaks effectively
  • Conditions cooling system
  • Inhibits rust and corrosion
  • Lubricates water pump seals
  • Helps control electrolysis


  • Lacks appropriate certification
  • Provides less lasting outcomes
  • Less viscous and hence not so effective

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6: Dike Temporary Radiator Stop Leak

Dike Temporary Radiator Stop Leak

If you are on the lookout for a sealant to use on a frequent or long-term basis, try your hand on this one. It is too powerful and never loses its potency easily as well. It is also contained in a durable and reliable container that hardly spills.

High Quantity

As hinted, the quantity of this sealant is pretty high. The sealant is in fact contained in a jerry can rather than a bottle as is the case with the other ones. It is this trait that suits for frequent and prolonged use. You will not have to purchase brand new ones every quite often.


Even though it has a higher capacity, it is nonetheless economical. You will only have to put in four ounces of the coolant for every four gallons capacity. This ratio sees to it that you do not waste too much of your coolant and suffer the attendant financial hardships.

Safer for the Engines

Unlike most other sealants, this one is designed in such a manner as not to slip into the engine. It is thus less likely to forms sludge and in so doing plug the oil passages do interfere with the smooth functioning of the engine.


  • Stops leaks in radiators in a matter of seconds
  • Helps gaskets seal better
  • Does not block small passages in coolant systems
  • Works well with all standard and permanent anti-freezes
  • Prevents water from seeping into the engine also


  • Inconvenient to carry around
  • Slightly complicated to engage
  • Not so reputable brand

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7: Prestone AS145 Radiator Sealer Stop Leak

Prestone AS145

A comprehensive sealant is by all means necessary for long distance travels. This is to take care of whichever eventuality that may befall you in the course of the journey. This sealant, by virtue of being able to impact the heater cores, water pumps, and radiators, fits the bill perfectly.

Excellent Formulation

Combining both the natural and the synthetic ingredients, this sealant has an excellent formulation indeed. This formulation is what grants it the ability to perform a vast array of engine related chores. It also makes the sealant able to seal extremely minute leaks.

Patented Formula

A patented formula comes in next. This formula basically allows the sealant to quickly stop leaks in the water pumps, radiators, and the heater cores. It also expedites time to a great extent in the process. This is not to mention the great outcomes it brings about.

Anti-corrosion Properties

Lastly, the sealant also has some anti-corrosion properties. This property basically protects the metallic components of the engine from corrosion and pitting. It slows down their deterioration and the attendant consequences of perforations.


  • Mitigates corrosion and pitting thoroughly
  • Can manage even large leaks without compromising the flow of the coolant
  • Deals with both the leak and the corrosion that causes the leaks
  • Has some fibrous particles that enhance the lifespan of the seals
  • Great for high-performance actions


  • Brings about limited returns to scale
  • Suitable for one-time use only
  • Exudes less potency

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8: AlumAseal ASBPI12-12PK

AlumAseal ASBPI12-12PK

To be on the safe side while taking a long journey, you must possess a sealant that confers universal applicability. This simply means that it has to perform a range of chores that are related to car maintenance and mechanic. This is that kind of sealant.

Maximum Compatibility

In all, this sealant is compatible with a vast range of coolants and anti-freeze substances. It works well with them and does not at all react adversely when in contact with these substances. This is the trait that returns the benefit of universal applicability.

Unbridled Convenience

With this sealant, you will be able to seal leaks and cooling systems as well. Other than this, you will also be able to confront up to 22 quarts (21 liters) of volume at a time. This is sufficiently large enough to effectively seal even the largest leak.

Extreme Safety

The benefits of maximum safety are yours to reap. Indeed this sealant is safe and extremely effective for all kinds of materials. These include but not limited to rubber cooling systems, plastic, and metal. You will hardly sustain corrosion and other dangers that these sealants pose.


  • Works faster and promptly
  • Prevents and repairs cooling system damage
  • Safe for use on metal, rubber, and plastic cooling systems
  • Guaranteed to work under all conditions
  • Does not clog your cooling systems


  • Too limited in scope and applicability
  • Not recommended for larger surfaces
  • Produces limited returns to scale

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9: Bar’s Leaks 1150 Grey Cooling System Repair

Bar’s Leaks 1150

Sealing leaks in your radiator ought not to be a hassle. This is especially if you choose to utilize this sealant. It negates the need for flushing out unwanted oil before use. This reduces the time taken for the feat to be accomplished besides calling for limited expertise on your part.

Premium Carbon Fiber

The premium carbon fiber formulation comes in first. This ingredient allows for extended protection to the engine and other vital parts of your vehicle. It, therefore, slows down the pace of deterioration and lengthens the lifespan of your car.

Utmost Compatibility

On the whole, the sealant pairs and works well with all kinds of other oils, coolants, anti-freeze, and sealants. These include the conventional green or blue and the extended life red, orange, and yellow coolants. You are assured of the benefit of maximum convenience.

Anti-leak Property

Other than sealing the radiator leaks, this sealant also stops cooling system leaks. Its dual purpose assures you of the convenience and functionality you require to enjoy your long journeys unhindered. You surely have no better friend than this for your long trips.


  • May be used on water alone
  • Backed by 70 years of experience
  • Has a track record of success and long history
  • Delivers the expected outcomes faster
  • Suits users of all skill levels and experiences


  • Requires some flushing before use
  • Complicated to utilize
  • Clumsy and hence calls for plenty of storage space

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10: J-B Weld DS-114 PERM-O-SEAL Radiator Stop Leak

 J-B Weld DS-114

Heavy commercial vehicles are ordinarily tough to confront. Their leaks are often too large and deep. This sealant is great for use in such circumstances. It can permanently repair leaks on trucks, buses, vans, and even tractors! The following mini-review lays bare its finer features.

Special Non-toxic Formulation

Coming in at position 1 is the special non-toxic formulation. The sealant is indeed safe on your hands and clothes. It is less likely to corrode your hands or clothes. It is, however, effective enough to confront every length and breadth of your radiator.

Powder Concentrate

It comes in the form of a powder concentrate rather than a fluid. For this reason, it is simpler and more convenient to store and transport. It is also economical in that it is easier to calibrate and use effectively for your applications.


The sealant does much more than just seal leaks. It also lubricates the metallic components and inhibits rust. This arrangement allows you to leverage so much more benefits than you would obtain from other sealants. It thus returns a higher value for money.


  • Brings about permanent end results
  • Quite economic in nature as compared to liquid-based competitors
  • Does not harm or clog the engine system
  • Possesses a water pump for added efficiency
  • Lubricates the radiator as well


  • Too elaborate to apply effectively
  • The limited capacity of just 1.6 ounces
  • Manufacturer warranty may not apply

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What is a Radiator Stop Leaks?

The radiation stop leak is the substance that helps you to achieve this feat. It is basically a sealant.

It possesses anti-corrosive properties. It plays the role of stopping and preventing leakages in the radiator and other components of the heating system.

Types of Radiator Stop Leaks

Radiator stop leaks may be classified according to the places where they may be employed. The following are the main types of radiator stop leaks:


These are used to seal devices that contain or hold petrol.

Workshop and Service

As the name suggests, this kind of radiator stop leaks is utilized in the workshop and the service premises.

Oil System

These are specifically geared towards sealing off the oil systems. They are very thick and viscous enough to prevent any percolations of substances.

Cooling System

Cooling system radiator stop leaks, as hinted, are the ones that are used exclusively for the purpose of stopping the radiators of the cooling systems from leaking.

Air Treatment

Lastly, these stop leaks may also be sued to seal containers from the escape of air. They basically make containers airtight.

When Should You Use Stop Leak?

The following are some of the major circumstances that necessitate the use of the radiator stop leaks:

Detected Leaks

In the event that you detect a leak on the radiator, do not hesitate to us the stop leaks. This, of course, is to prevent the spill of the liquid and fuel from the concerned parts of the engine.

Before a Long Journey

Before you commence a long journey by car, you are advised to apply the stop leak. This is to act as a preventive measure against any possible leaks. This way, your car will less likely sustain any leaks in the course of the journey.

Routine Repairs and Maintenance

From time to time, you will usually have to carry out repairs and maintenance. At such times, you inevitably have to apply these estop leaks as part of the repair process. This again is a preventive rather than a curative process.

Before Storage

The metallic portions of cars and other gadgets are more likely to sustain leaks and perforations while in storage. This is why you want to apply these stop leaks moment before you store the car for longer. This is to prevent any leaks from widening significantly.

Replacement of Parts

Apart from regular repairs and maintenance, you will often have to replace the various parts of the engines. This is yet another circumstance where applying the stop leak makes sense. Do so in order to give your engine a fresh breath of life.

How Does a Radiator Stop Leak Work?

A radiator stop leak is generally designed to soften and expand the rubber seals to keep them fresh and functional at all times. The leaks are waterproof and airtight at the same time.

This enables them to completely block the percolation of water and moisture into and out of the engine. It is this trait that makes them able to prevent liquid contents from leaking from the radiators of engines.

How to Use a Radiator Stop Leak Effectively?

Store in a Cool and Dry Place

Radiator stop leaks are sensitive to external environmental temperatures. They tend to solidify when subjected to extreme cold and melt when exposed to extreme heat. In light of this, you should store it in a cool dry place when not in use.

Keep off the reach of Children

These substances are toxic. You do not want them anywhere near your children. On the contrary, you want to safeguard your children from them as much as possible. This is why you want to keep them off the reach of your children at all times.

Seal tightly when not in Use

Other than keeping them off the reach of your children, you also want to seal them tightly. The smell they emit to the external ambiance may block the nose of the people who breathe the affected air. This might lead to respiratory tract infections and possible damages to the lungs.

Use Moderately

Use the sealant moderately. Too much use may end up corroding the metallic parts of the engine wherein it is applied. Such a practice also drains the sealant quickly and inflicts higher costs on your part. Moderate use guarantees long-term reliability.

Put on Protective Attire

Always remember to put on the relevant protective attire. These include the gloves, goggles, aprons, and face mask. You want to minimize any direct contacts with the sealant as much as you can. You do not want to be poisoned by the sealant, would you?

Top Brands

In this year, the following are the top radiator stop leak brands on the market:

  • ATP
  • Bar’s Leak
  • K-Seal
  • Dike
  • Prestone
  • AlumAseal
  • J-B Weld

Radiator Leaking Symptoms

The following are some of the top signs and symptoms of the radiator leaks:

Drop in Coolant Level

If the level of the coolant in the radiator drops too low, it may be a sign that the radiator has sustained a leak. To mitigate this problem, you have to carry out regular checks to keep the pace with the levels of the coolant. This way, you will be able to detect any impending drops.

Puddle beneath the Engine

In case you spot a puddle usually of petrol or fuel beneath the engine, this could yet again signify the existence of a leak in the radiator. The puddle in question may often arise from the fuel that finds its way through the small cracks and perforations.

Discoloration or Corrosion

When the fuel droplets get into contact with the metallic parts of the engine, the said parts often get discolored. This, therefore, means that in case you spot any discoloration on the said parts of the car, this might be a sign that a leak is not so far from that place.

Faulty Radiator Hoses

The radiator hose is the pipe that furnishes the coolant to the radiator. If the hose sustains a leak, it will usually be faulty. This compromises its ability to channel the coolants to the radiators as reliably as need be. Be on the lookout also for any possible faults in the radiator hoses.

Frequent Engine Overheating

As explained above, the primary role of the radiator is to cool the engine. It, therefore, follows that should an engine overheat unnecessarily, this could be indicative of the fact that the radiator might have issues. One of these issues could be that there is a leak in the system.

How to Fix Radiator Stop Leak?

Switch off the Engine and let it Cool

Start off by switching off the engine. Proceed thereafter to let it cool. After the engine is completely cold, remove the radiator cap. Do not attempt to touch the radiator when it is hot.

Identify the location and extent of the leak

After the engine has cooled, proceed to identify the precise location as well as the overall extent of the leak. These two shall determine where and how much of the radiator stop leak to apply.

Clean the Radiator

Before applying the radiator stop leak, you need to clean the radiator. Use a hosepipe to do this. Cleaning the radiator is necessary as it gets rid of the debris that might compromise the efficacy of the stop leak and render it less effective.

Apply the radiator stop leak

Now proceed to apply the radiator stop leak appropriately. Focus on the affected portions of the radiators. Vary the quantity in response to the size of the leaks themselves. This is the most important step, so pay particular attention to it. Leave the adhesive to cool for some time.

Test the Seal

You should finish off by testing the seal. This is to find out whether the adhesive has indeed sealed the leak or not. Do this by driving the vehicle around and stopping intermittently to check the status of the radiator. Make appropriate adjustments if need be.

What should I Look for When Buying a Radiator Stop Leak?


Certain brands and manufacturers have consistently proved reliable and great. The ATP, Bar’s Leak, K-Seal, Dike, Prestone, AlumAseal, and J-B Weld are by far the best of these brands. In your search for the right radiator stop leak, do give them a higher priority.

Cost vs. financial resource endowment

You should ascertain the amount of money at your disposal first and foremost. You should thereafter proceed to find a sealant that fits within your budget. You do not have to dig too deep to be able to afford your sealant of choice, do you?


These sealants vary by their formulation. Some are potent yet others are weak. Those that are potent are intended for larger leaks and for a prolonged duration of time. The weaker ones are for quick-fix solutions. The choice of these two extremes is absolutely yours.

The extent of the problem at hand

How large are the leaks? Larger leaks require more potent radiator stop leaks. This is because of the need to put in place an effective barrier to ward off the percolation of water and air. Weaker stop leaks will do for smaller holes or perforations.

Frequency of Use

How often do you intend to use the radiator stop leak? Is it one time only? Alternatively, do you plan to use the stop leak repeatedly or for a prolonged duration of time? The quantity of the leak is what determines its suitability for this role. Choose a large quantity one for repeated use and vice versa.


What are some of the dangers of the radiator stop leak?

If inhaled, they have the ability to inflict respiratory tract infections alongside other issues. They may also corrode the metallic surfaces besides inflicting damages to the skin. This is why you have to put on protective attire while engaging it.

Are these products really reliable?

YES, they are! They are stronger than epoxy and easier to apply. This is not to mention also that they are cheaper to afford on the whole.

How long does this stop leak last on average?

Most of them will last you a couple of weeks. They can only take you that far. For this reason, you will have to make the complete repair of the leaks a priority as soon as you can.

I have been using these substances for quite some time now with no success. What could be the problem?

The potency of the said sealant may have diminished by reason of wear and tear. Alternatively, you may have applied it on a specific portion of the radiation for too long. Consider replacing the affected portion of the radiator or sealing the leak using a mechanical alternative.

Final Verdict

My favorite is J-B Weld DS-114 PERM-O-SEAL Radiator Stop Leak – 0.7 oz. As you may well have noted, it is comprehensive in scope by virtue of being able to handle all kinds of engine related chores.

It is also availed in powder rather than fluid form. This makes it safer and more convenient to store and use. You will more likely obtain a higher value for money by settling for it.


The Team That Worked On This Review

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