The 10 Best Radiator Stop Leaks of 2021

Jerry Wilson
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Sick of how long it takes your car to warm up in the morning?

Before you jump to conclusions with your local mechanic, first ask yourself, “is it my engine oil or my radiator that’s leaking?”

Radiator engine coolant leaks are one of the most common reasons for a fast-smoking car.

There are many products out there claiming to stop radiator leaking fast, but with so many different products out there it can be hard to know which stop leak to use.

Below are the 10 best radiator stop leak liquids available in 2021.

NameCategoryProduct
Dike Temporary Radiator Stop LeakBest OverallDike Temporary Radiator Stop Leak
Bar's Leaks HDC Radiator Stop Leak TabletBudget PickBar's Leaks HDC Radiator Stop Leak Tablet
ATP AT-205 Re-Seal Stops LeaksUpgrade PickATP AT-205 Re-Seal Stops Leaks

1. Dike Temporary Radiator Stop Leak

Our rating: 9 / 10

Dike Temporary Radiator Stop Leak

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Pros:

  • Will stop leaks from radiators, water pumps, hoses, transmission coolers, oil coolers, and so on
  • Saves money by extending the lifespan of your car’s engine
  • Excellent reviews

If you’re looking to solve your radiator leak for good, Dike’s Temporary Radiator Stop Leak is the product to use. It’s popular among many people due to the fact that it’s inexpensive and it does the job quickly.

Most people notice their radiator leak after they’ve had a bad snow storm or a winter trip. In case you’re wondering, the engine warms up, and the water expands and causes the leak. It’s always best to stop the leak before you start driving. This product can be the temporary solution to your leak before you get the permanent fix.

You can use Dike Temporary radiator stop leak to extend the life of your car. You can also use it to avoid expensive repair bills. It’s also worth noting that Dike’s Temporary Radiator Stop Leak is clean, non-toxic, and non-flammable.

2. InterDynamics Certified AC Pro Radiator Leak Detector Dye

Our rating: 8 / 10

InterDynamics Certified AC Pro Radiator Leak Detector Dye

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Pros:

  • Easy to use and apply
  • Effective against the most persistent radiator leaks
  • Completely compatible with the fuel lines, belts, upholstery, and rubber hoses

Cons:

  • Bottles are flimsy and can break easily
  • Not suitable for cars with under-bonnet radiators

One of the most reliable and time-tested radiator leak detection products is the InterDynamics Certified AC Pro Radiator Leak Detector Dye for Cars & Trucks & More, 1 Oz, 375CS, Engine Cooling Systems UV Dye, Universal Purple.

The reason why I chose this radiator leak detection product above all the others is due to the reliability of the product and the fact that it actually works. It is made from a high-grade formula using a UV dye that is both light and stain resistant. It is also completely compatible with all engine fluids, including the transmission oil and the fuel lines.

Just keep in mind while applying the product that you should only do it when your car is warm so that the leak shows up more clearly.

3. Bar's Leaks 1186 Liquid Aluminum Stop Leak

Our rating: 8 / 10

Bar's Leaks 1186 Liquid Aluminum Stop Leak

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Pros:

  • Cheapest of the bunch
  • Inexpensive and easy to use
  • Fast-acting (instantly treats the cooling system)

Cons:

  • Doesn’t work with every car model
  • Product provided by the manufacturer

It’s important to note Bar’s Leaks 1186 Liquid Aluminum is a chemicoolant, meaning it is formulated to treat the engine as a whole, rather than a single part. Chemicoolants use a variety of highly reactive chemicals to dissolve rust and corrosion and stop leaks for good.

Bar’s Leaks 1186 Liquid Aluminum Stop Leak is effective because it forms a protective layer in the cooling system of your car that prevents the build-up of rust and corrosion, and it helps to seal leaks for good.

This product has officially been recommended to several major automotive manufacturers by the Global Institute For Automotive Service Excellence (a.k.a. ASE).

4. Bar's Leaks HDC Radiator Stop Leak Tablet

Our rating: 8 / 10

Bar's Leaks HDC Radiator Stop Leak Tablet

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Pros:

  • Easy to use
  • Ideal for all radiators
  • Cost effective – least expensive on the list
  • Green product
  • Turns clear after leaker has been stopped
  • Made in the USA
  • Give your cooling system a boost!

Cons:

  • Not easy to find in some areas
  • Doesn’t always work on tough leaks, especially over long periods of time

The coolant stop leak is an effective tool to fix your radiator leak if you no longer have to replace the entire system. The liquid you put in your system will fill up all the cracks in the leaking system and set up a barrier to stop the leakage. This is the reason why you have to flush your system again after you have fixed the leak.

For this reason, some forums recommend against stop-leak and advise you to replace your entire cooling system if it leaks. However, we’re going to show you why the coolant stop leaks are great for many common problems that you experience with radiator leaks.

Of course, if you don’t pay attention to what you do, you can end up causing more damage to your car. There are more benefits and drawbacks that we will talk about.

5. ATP AT-205 Re-Seal Stops Leaks

Our rating: 8 / 10

ATP AT-205 Re-Seal Stops Leaks

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Pros:

  • Great Performance
  • Easy to install
  • Great bang for your buck

If you’re looking for a cheaper alternative, the AT-205 Re-Seal Stops Leaks from ATP is an easy choice. It eliminates leaks without the hassle of taking your car to a mechanic.

This product comes in a convenient spray can and is applied using a spray nozzle attached to the can. One way you can apply this product is by spraying it into your radiator cap to stop the leak. Another way is by simply spraying the liquid over the leak.

The mist spray goes on easily and dries quickly, and there’s no need to go over the leak multiple times as you may have to with other products.

6. AlumAseal ASBPI12 Radiator Stop Leak Powder Blister Card

Our rating: 8 / 10

AlumAseal ASBPI12 Radiator Stop Leak Powder Blister Card

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Pros:

  • Can be used on all metals
  • Safe for using inside the engine compartment
  • Comes in a durable blister card container

This is one of the most trusted ways to treat your radiators and make them last longer. It is a powder that you add to your engine to stop leaks internally. It comes in a compact pouch that is very durable and easy to carry in your car. The package even has a small compartment for storing the measuring syringe. The aluminum powder comes in a flush-able wrapper that can be flushed out of your radiator at the end of use.

The packet contains a 20 g packet of the powder that can be used to 125 gallons of water. It comes in a resealable foil package that stays waterproof for later use. Despite the powder being a mild irritant to the skin, it can still be used in open engine compartments. It comes in many sizes so you can choose how much you will use.

7. K-SEAL Coolant Leak Repair

Our rating: 8 / 10

K-SEAL Coolant Leak Repair

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Pros:

  • Multipurpose formula.
  • Doesn’t require mixing.
  • Can be used as a flush additive.
  • Can be used as a preventive additive.
  • Produces less foam.
  • Good pricing for the quantity.

Cons:

  • Works, but doesn’t always work.
  • Quantity may not be enough.
  • Doesn’t work in every situation.

In Minutes!

8. Bar's Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak

Our rating: 8 / 10

Bar's Leaks 1109 Block Seal Liquid Copper Intake and Radiator Stop Leak

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Pros:

  • Easy to use
  • Minimal risk of burning yourself

We’re all familiar with Bar’s Leaks. Everyone has used this product at least once, but not everyone understands how it works. The manufacturers of this product state that it fills in the pinhole leaks in the intake valves, exhaust valves, and water passages.

Bar’s Leaks also states that this product improves gas mileage and performance by preventing water from entering the combustion chambers…… By increasing compression. According to reviews, the product works a bit differently for different people, but the general consensus is that the product works well at restoring performance to engines.

The Bar’s Leaks website states that the product stops leaks that are caused by rust. Nearly everyone has had their exhaust rusted, but most of us haven’t bothered to fix it because it’s an expensive fix. Well, this product could be cheaper for you than the exhaust fix.

9. Prestone AS145 Radiator Sealer Stop Leak

Our rating: 7 / 10

Prestone AS145 Radiator Sealer Stop Leak

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Pros:

  • Budget-friendly
  • Offers long-lasting solution for slow leaks
  • Aids in sealing cracks and crevices

Cons:

  • Contains petroleum and siloxanes, which can be harmful to the environment
  • Can cause skin irritation to sensitive people

Our pick for the 10 best radiator stop leaks of 2020 is the Prestone AS145 Radiator Stop Leak. It is a non-acidic formula used for sealing cracks, crevices, and holes in all radiator systems. This product is a great alternative to OEM sealants. In addition, Prestone AS145 comes in different sizes depending on your needs.

This product is also budget-friendly and can be used to eliminate small holes in the radiator quickly. You can patch a slow leak or a small leak without having to buy a whole new radiator. Moreover, there is no need for you to drain the coolant.

According to customer reviews, Prestone AS145 offers long-lasting solution to slow leaks, a convenient way to seal holes in the radiator, and it also contains petroleum and siloxanes, which can be harmful to the environment if spilled. However, it’s better than buying a whole new radiator.

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

Our rating: 7 / 10

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

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Pros:

  • Great reviews
  • Affordable
  • Lots of product choices

Cons:

  • Fitting can be tricky
  • Requires total removal of the radiator

There’s nothing worse than a broken down car, especially in the middle of nowhere. However, with J-B Weld DS-114 PERM-O-Seal Radiator Stop Leak you can fix the problem.

This radiator stop leak is a powerful solution to fix a radiator leak problem fast. It’s flexible, so it allows repairs that you don’t have the tools for.

It comes in a 0.7oz tube with an inside diameter of 1.2 inches. To be able to use the product, you need to remove the radiator cap, then flush the radiator and let it dry.

Frequently Asked Questions (FAQ)

What is the best radiator stop leak?

Many radiator stop leaks and preventative products are specifically designed to prevent an engine overheating. While there are a few stop leaks generalized for radiator repair, they’re not what we’d prescribe for leak repair. These tend to shrink seals and can cause more problems than they solve.

Instead, we suggest using standard car radiator repair, additives. These chemicals can help stop radiator leaks or can help the radiator put pressure back into the system while it’s out of the vehicle.

Before you buy, you’ll want to be sure you’re choosing a product that’s compatible with your vehicle. Almost all of these products feature very straight”forward instructions to make installation a breeze. Be sure to follow the directions carefully to ensure the best fit possible.

What is the best radiator sealer?

If your radiator leaks, you need to stop the leak! If you have coolant leaks from your cooling system or from your water pump, you can use a radiator sealer to stop the leaks before any damage is done to your new car.

Radiator sealers are designed to stop leaks inside your cooling system. They do this by forming a permanent, thermally conductive, and corrosion-free seal on your radiator. These sealers work to stop leaks and make your radiator more efficient, less prone to further leaks, and more resistant to corrosion.

Annual maintenance and radiator repairs are inevitable. An annual treatment of radiator sealer will help extend the life of your cooling system by delaying the need for major repairs and replacement.

What is the best stop leak for a blown head gasket?

Bosch is the king of gasket sealers. The product is easy use, and it works extremely well.

RadBolt is a great choice for fixing a blown head gasket. The gasket is infused into the threads of the bolt.

The seal is enhanced with an anti-seize coating, and the bolt is packed in corrosion resistant oil.

Wurth has made gasket sealant for a variety of different products for decades. Like any good gasket sealer, it is odorless and contains no silicone. The product contains an antioxidant and a special agent that dries paint.

This anti-corrosion seal is easy use and high performing. The hardness of the product adjusts to the size of the gasket, and it’s easy to clean up.

How do you seal a leaking radiator?

First, you need to determine the cause of the leak. If the radiator is leaking from a damaged seal or gasket or because the hose is leaking or cracked, then you will need to replace the damaged part. If your radiator is leaking on the inside, then you need to determine whether or not it’s leaking from a crack or hole in the tank. If it is, then it’s best to replace the tank.

Inspect the outside of your radiator. If you notice any black marks or oil stains on the outside, you could have a leak inside the tank. Carefully remove your thermostat to inspect the inside of the tank and the tank cap to inspect the cap and tank neck.

Conclusion

We evaluated many different radiator stop leak products and found that some work much better than others. We are confident that our list will help you avoid any bad purchases. We hope that you found our guide incredibly helpful, and if you want to test only the best then this list is a good place to look for products that you can trust and rely on. Here are the results of our research, and we hope they help you prevent this problem from occurring in your vehicle.

Our Recommendation

NameCategoryProduct
Dike Temporary Radiator Stop LeakBest OverallDike Temporary Radiator Stop Leak
Bar's Leaks HDC Radiator Stop Leak TabletBudget PickBar's Leaks HDC Radiator Stop Leak Tablet
ATP AT-205 Re-Seal Stops LeaksUpgrade PickATP AT-205 Re-Seal Stops Leaks