10 Best Radiator Stop Leak in 2019


Radiator is a traditional element of automobile cooling system as well as home heating system, which can be applied differently depending on where it’s used. Car radiator serves for engine cooling, transmitting motor’s heat through the water. It provokes water heating and, consequently, heats up air, entering the cabin. Home radiators function very similar by transmitting hot water or liquid through the pipes to heat up the air in the room.

As radiators contain liquids, it’s crucial to inspect your radiator regularly and cease any leaks if they start. Talking about car radiators, when you notice water under the front of your automobile when it’s parked, it means that your radiator leaks.

All metallic parts of radiator, utilized for liquid transmitting, can be subjected to leakage, resulting in pressure decrease, corrosion of the zone close to leak plus reduced overall performance of the cooling system. Actually, vacuum based systems may lose much heating because of leakage troubles.

In case if valves leak, it’s required to exchange the details as the problem can’t be fixed by simple repairing. If piping system leaks, it’s easier to get rid of this defect. Usually, patches are fixed mechanically. Or, if you need immediate fixing, you are free to purchase a stop leak radiator liquid or powder, which will seal the hole for some time until you will have time for major repairs.

And now, we are eager to introduce ten outstanding radiator stop leak items. This list was formed according to various reviews along with real tests, held to discover what items are really efficient and what are just waste of money.

Top radiator stop leaks review


#10 Prestone AS145 Radiator Stop Leak

Editor’s Rating: 4 out of 5 stars (4 / 5)

prestone AS145 radiator stop leakThat’s definitely a great solution of leakage problems. Being patented by a prominent brand, this formula reaches the desirable result every time it’s applied. It provides immediate assistance and stops any leaks quick and efficiently, allowing you to drive a car having no worries about radiator.

Besides, Prestone AS145 is able to avert corrosion in the cooling system. As corrosion may lead to leakage, by preventing corrosion you will decrease the chances to face any serious leak. Consequently, your automobile will function steadily and effectively.

In case of bad seals, this item may increase their functionality by renovating them. So, this product is very useful and is easy to use. It will help to get rid of leaks up to 0.020×0.5 inches.



#9 Alumaseal ASBPI12 Radiator Stop Leak Powder Blister Card

Editor’s Rating: 4 out of 5 stars (4 / 5)

alumaseal ASBPI12Alumaseal Radiator Stop Leak Powder Blister Card is pretty affordable, but is often sold as an additional item to other orders. Besides, you are free to purchase brand’s clip strip of 12 blister cards.

This item can be utilized for every material and is compatible with every coolant type and anti-freeze additions in cooling system. Be sure that it won’t block the vehicle’s cooling system.

Besides, it’s easy to use. After pouring the powder into radiator, make certain that it’s not warm before you take away the cap. After closing the cap, make the motor run for several minutes. This item will be efficient for radiator coolants up to 22 quarts.



#8 BlueDevil Radiator & Block Sealer

Editor’s Rating: 4.1 out of 5 stars (4.1 / 5)

BLUEDEVIL RADIATOR & BLOCK SEALERBeing created in the United States as a continuous resolution for radiator and block leaks, this radiator and block sealer is apt to save you from any leakage. Creators of this product assure that it performs permanent repairs and is applicable for plastic, aluminum plus metal radiators along with being absolutely safe plus non-difficult in use.

Thanks to its special composition featuring no tough and filamentary materials, the sealant makes no damage or block to the cooling system. It attaches to plastic, aluminum, metal and cast iron along with being appropriate for gasoline and diesel motors. Once, it finds the weak spots of the cooling system, it attaches to them, creating a permanent seal, functioning in connection with the motor heat, expanding and contracting. The item can be poured straight into the cooling system and no additional steps are required.



#7 Genuine GM Fluid 3634621 Cooling System Seal

Editor’s Rating: 4.2 out of 5 stars (4.2 / 5)

GENUINE GM FLUID 3634621 COOLING SYSTEM SEALThis item is available in the form of pellets and serves as a non-expensive and efficient remedy.

Furthermore, this sealant is commonly added to the GM vehicles during the manufacture process to avert any hairline fractures, which may appear in the radiator.

Principally, this cooling system seal is employed for aluminum radiators, but it goes well with other materials, including copper. During the tests, these tablets didn’t cause any harm to test automobiles.

Bear in mind that you need to discover the amount of coolant in the system and add a determined amount of sealant, which may be bulkier in comparison with liquid substances and cause some inconveniences while being added. Thus, you’d better find out the amount of sealant you need prior to start adding it to the radiator.

This item is an outstanding remedy for hairline fractures, but it’s not created for serious leak. It serves as a temporary resolution of the trouble and even after applying it, turn to a professional at the first opportunity.

Besides, it’s not clear how long such seal will perform its functions. It can cover pretty large holes and provide immediate assistance in case of emergency, but don’t count on its durability. If to talk about small leaks, these pellets can serve longer, but still not permanently.



#6 J-B Weld DS-114 Perm-O-Seal Radiator Stop Leak

Editor’s Rating: 4.3 out of 5 stars (4.3 / 5)

J-B WELD DS-114 PERM-O-SEAL RADIATOR STOP LEAKBy acquiring this item, you can be sure in its excellent quality. Being absolutely non-difficult in application, this harmless sealant will efficiently cope with any leaks. Moreover, it is apt to perform the functions of a rust inhibitor along with lubricating the internal cooling system.

Its main advantage is that it’s able to ensure a permanent solution to the leakage issues no matter if you have a car, truck, van, bus or anything else.

Being regarded as one of the greatest sealants in comparison with liquid substances, this J-B Weld product will provide you with good quality repairs at reasonable money. What makes it even more astonishing is that it causes no block or harm to the cooling system.



#5 Dike Temporary Radiator Stop Leak

Editor’s Rating: 4.4 out of 5 stars (4.4 / 5)

DIKE TEMPORARY RADIATOR STOP LEAKThis Dike item is the appropriate product for immediate and fast repairs in emergency cases. Besides, it may serve to prevent damages of any system, functioning under difficult conditions.

It goes well with every kind of radiator coolants, including green and orange ones. Additionally, it can be utilized for radiators of any vehicle, from a mini car to a van or tractor.

Manufacturer advises to add 1 pint for every 4 gallons of radiator’s capacity or 4 ounces per each gallon. Just add the necessary amount of sealant to the radiator, change the radiator cap and run the motor for about 15 minutes.

The item functions efficiently thanks to its innovative formula, which seals any leak it finds, protecting the automobile and maintaining necessary temperatures.



#4 Bar’s Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak

Editor’s Rating: 4.5 out of 5 stars (4.5 / 5)

Bar's Leaks 1109 Liquid Copper Radiator Stop LeakOld versions of automobiles frequently keep copper radiators. If your radiator is made of copper, you must be very careful with the choice of the proper products as this material may cause problems for some sealants.

This Bar’s block seal liquid is good for temporary repairs of copper radiators, having no bad impact on the cooling system.

Bear in mind that the item may face difficulties in dealing with big leaks or coolant leaking on the driveway as it was initially created for pinholes and hairline cracks.  Though, it’s very efficient for minor leaks.

Though this sealant is marketed to cope with block fixing, no mechanics advise to apply any chemical fixes for block until you are forced to do that in the worst extremity and have no opportunity for a real fix.

Still, if it’s just used as radiator stop leak, it’s rather reliable and can serve as a temporary resolution of the problem for a week or two until you are prepared to acquire a new radiator.

Thus, this item is suitable if you have a copper radiator featuring minor leaks. It will avert expansion of damage until a fresh radiator is installed.



#3 ATP AT-205 8-Oz Re-Seal Bottle

Editor’s Rating: 4.7 out of 5 stars (4.7 / 5)

ATP AT-205 8-OZ RE-SEAL BOTTLEIt’s the proper choice if you need non-toxic plus quick sealant. Basically, this item is high-quality professional liquid apt to provide you with efficient assistance. Besides sealing leaks, it also renovates rubber seals and gaskets, gearbox, power steering plus hydraulic systems. This item is able to regenerate outworn or dry seals without harming any internal elements. Additionally, it functions decently with conventional and synthetic oils, hydraulic oil, gear oil, ATF and power steering fluids.

As the liquid is absolutely non-difficult to use, you simply need to add the sealant to the radiator as you usually do with oil or brake fluid. It functions by mixing up with the oil and circulating when the motor is run. Being made of plasticizer, this product hardens and raises flexibility. If the seal and gasket are in order, this liquid starts its effect in 5 hours after you add it.



#2 Bar’s Leaks 1186 Liquid Aluminum Stop Leak

Editor’s Rating: 4.8 out of 5 stars (4.8 / 5)

BAR’S LEAKS 1186 LIQUID ALUMINUM STOP LEAKHaving being in business for a while, Bar’s Leak brand has already created many formulas for various kinds of radiators.

Specifically this product is applicable for aluminum radiators and it’s not recommended for others. The sealant may also seal outside leaks in hoses or other elements of the cooling system and is known for its efficient work.

This item copes great with slow leaks while its efficiency with heavy leakage may be reduced. It’s apt to seal hairline cracks pretty fast along with dealing with some more serious problems. However, during tests, it didn’t master to seal the majority of radiators, K-Seal coped with.

If to apply this item correctly, you can prolong the lifespan of your radiator for a week or two. Though, you will still need to acquire a fresh radiator.

This sealant is a good choice for aluminum radiators and slow leak troubles. It’s possible to seal the leak easily and for a while if to follow all the instructions.



#1 K-Seal ST5501 Permanent Radiator Stop Leak

Editor’s Rating: 5 out of 5 stars (5 / 5)

K-Seal is one of the most experienced manufacturers of stop leak and knows how to create top quality sealants. Dealing with liquid sealants, brand offers products safe for all types of radiators. And tests proved that this stop leak doesn’t harm any radiator.

Being trusted by many car owners and professionals, this item is believed to have a good impact on the entire cooling system. During the tests, the radiators were in great condition after damages had been repaired. Though, it’s not clear if the further action was favorable.

Be ready that this sealant may be rather costly and, actually, it’s one of the most expensive solutions for leakage problems. Thus, you’d better use it only for small leak and if you know what exact kind of radiator you own.

Additionally, this item has a long-lasting effect though there is no assurance that it can serve as a permanent solution of the problem. So, it’s still recommended to acquire a fresh radiator, especially if you plan a long journey.

Apparently, K-Seal is the most efficient tool for dealing with radiator leaks. It’s apt to fix serious problems as well as give a long-lasting effect. Nevertheless, it’s still a temporary solution of the radiator damage.



What’s Important to Know While Opting for a Radiator Stop Leak?

Having read the reviews above, you may come to the idea that K-Seal ST5501 is the most proper option. It copes with leaks of any size and is applicable for almost every model of a radiator as a temporary resolution until you are able to substitute the radiator.

Many people consider stop leak to be car snake oil, but, actually, the main function of many products is to prevent the expansion of a gap and give you some additional time for buying a new radiator. No more.

Having read our reviews, you already know what sealants work the best for various types of radiators, what exact functions they perform, what troubles they may solve and how long their effect lasts. The most important for you is to make certain that the item you choose is suitable for your radiator.

We can’t tell for sure, but the stop leaks, which were created for a certain type of a radiator, may be more efficient. Yet, their limited functions are a sign of a more accurate chemical reaction.

Meanwhile, sealants in the form of powder or pellets are usually more affordable. Giving the identical effect as their liquid rivals, these sealants are more lightweight after being dissolved. Moreover, they don’t occupy much place in a car if you plan to store them there for extreme cases.

Nevertheless, liquids are easier to use as they usually created to suit a specific size of the cooling system while some pellets may be rather bulky.

Anyway, no matter what exact product you choose, any of them will provide you with immediate assistance in the worst extremity and will seal the leak efficiently, prolonging the durability of a radiator and allowing you to drive for some time before its replacement.

Tips on Radiator Stop Leak Use

Aspiring to cope with the problem fast and efficiently, make certain that you act according to the instructions on the sealant package as well as some general outlines. Proportions of stop leak may be different for various radiators and there can be some additional guidelines like shaking the bottle or something else. Besides, powders and tablets may have some specific directions in comparison with liquids. Always stick to the amount of sealant, advised by the manufacturer. Don’t use too little or too much as you may fail to reach the desirable effect, breaking the application rules.

To start, allow the automobile to cool down and take off the radiator cap. Never do that immediately after making a stop as steam may be directed just into your face. Crack the pressure deliberately. Never hurry up while doing that.

Add the stop leak to the radiator and warm up the motor to its normal temperature. By watching the ground under your car, you will notice when the leakage stops. After that, run the motor for several minutes more before turning off the ignition.

Not all manufacturers write that on packages, but it’s advisable to flush the system until it gets cool as no one needs the presence of some extra fibers or low melting point metals in the radiator. Some sealants may block the radiator or have some other negative impacts on it. So, never consider sealants as permanent resolution of the trouble and always read reviews before buying them.

To be on the safe side, you are free to flush the entire system one more time and only after that, add antifreeze to the cooling system. Clearly, it’s better to use the liquids, recommended by the auto manufacturer.

It’s crucial to examine the temperature and fluid level regularly until you acquire a fresh radiator. The sooner you substitute a radiator the better. Clearly, sealants may make your radiator function properly for a great number of miles, but no guarantees are provided and sooner or later the problem will emerge again.

Bear in mind that all tests were made, strictly following the guidelines and proportions, recommended by stop leak producers. Effect can differ if you apply the sealants in other proportions and fail to follow other directions. Moreover, there can be no effect at all if guidelines aren’t followed.


To Sum It Up

In a nutshell, K-Seal products remain the most reliable ones and provide the most long-lasting effect. That’s why, we recommend using ST5501 stop leak. Of course, this sealant is rather pricey, but it can be employed one more time. You are free to store it in your garage or automobile for immediate assistance in extremity cases. Moreover, don’t forget to take it with you if you plan a long journey as it can be a real wonder stick if you are far away from city and any automotive shop.

All the other sealants can be used as well. But bear in mind that no stop leak will be able to restore the radiator entirely and be a permanent solution of the leakage problem. All of them are just temporary fixes and no one knows how much a car can run after such a repair. So, start to seek for a new radiator in any case no matter what sealant you use to cover the gap in the radiator.

Written by Andrew Price

Andrew Price

Andrew is our top-rated author since 2019. He’s a big car enthusiast and customisation pro, who knows how to get more performance from your car.
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