Best Radiator Stop Leak

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.

But what is a radiator stop leak sealant and how exactly does it work? It’s also quite controversial and a lot of people will tell you to avoid it. Are they right?

Below we’ve listed our favorite stop leak sealants and answered your frequently asked questions. You’ll have a better idea by the end of the article what stop leak sealant is best for you and also what makes them work so effectively.

You’ll also understand exactly how they work miracles on leaks and can save you a fair few dollars.

Types of Radiator Stop Leak

Years ago radiator stop leaks would essentially stick the leak back together using gummy solutions and whilst this did temporarily fix the problem, it also caused issues in that it would also clog the cooling system passageways and heater cores – not ideal! Vehicles have become more high-tech over the years and therefore so have radiator stop leak products.

There are many different options on the market which provide different features and knowing which is the right choice for you can be difficult. Stop leak formulas are now made from a variety of different chemicals that can provide a permanent seal to your leak.

Many of the products on the market have now been created with steel, aluminum, and copper which bind to make the seal. Liquid forms and tablet forms are available too – offering protection for varying levels of leakage. Check the material of your radiator and know your car and which fluids you use to maintain it before purchasing a radiator stop leak sealant.

5 Best Radiator Stop Leak of 2021:

Bar’s Leaks Liquid Aluminium Stop Leak2.6 x 2.6 x 7.4 in1.2 pounds
K-Seal Permanent Coolant Leak Repair7.87 x 2 x 6 in9.6 ounces
Bar’s Leaks HDC Radiator Stop Leak Tablets7.5 x 5 x 0.8 in3.2 ounces
Prestone Radiator Stop Leak1.9 x 3 x 5.6 in13.1 ounces
Genuine GM Fluid 36346216 x 3.7 x 0.67 in1.06 ounces

1. Bar’s Leaks Liquid Aluminium

Bar’s Leaks Liquid Aluminium Stop Leak

Leaking liquid aluminum blocking leaks is one of the most well-known and popular coolant stop leaks.

It does this by using two key components to cool the water temperature: liquid aluminum and Xtreme Cool.

Well, Not only solves your problems, but also prevents further corrosion.


A good feature of this product is that your liquid aluminum is suitable for all different types of coolant: yellow, orange, pink.

And the antifreeze must be flushed out of the system before use because it can be added directly to the cooling system.

Overall, The leak seals within 20 minutes, but more often it does not seal red.

Pros /Cons
  • Works with all different types of coolant
  • It also works with water
  • Can be directly added to the cooling system
  • Have to flush the antifreeze out of your system before using

2. K-Seal Permanent Coolant Leak Repair

K-Seal Permanent Coolant Leak Repair

You may have many reasons to find the best radiator sealant.

This product can solve your problem quickly and professionally, for a fraction of the price.

It s a simple product to use as you just need to add the K-Seal to your coolant system to create a fast and long-lasting fix.

And it also has been scientifically tested and is the only coolant leak repair fluid carried by AA.

The product starts working immediately, looking for holes and cracks to permanently fix your engine.

Because it is made of a special material containing microfibers that come into contact with the gap and mesh together to form a seal.

Furthermore this product can repair holes up to 0.635mm in size, but does not block any channels or pipes in the cooling system.

Pros /Cons
  • It is simple to operate
  • All types of engine is treated with it
  • The car looks dirty after the addition
  • Water pipes cannot be fixed with it

3. Bar’s Leaks HDC

Bar’s Leaks HDC Radiator Stop Leak Tablets

Using a radiator leak tablet is one of the cheapest but most effective solutions you can find when plugging holes in the coolant system.

With these tablets, you can get all the benefits they might offer, and it is easy to use.

All you need to do with these outstanding products is mix them into an antifreeze solution and fill up your radiator or leaky cooling system.

Once you’ve changed the lid, you can drive and the tablet will do the rest of the work for you.

In addition, these pills offer the added benefits of a lubrication system, so fluids can flow more easily around your system.

And minimizing the risk of blockage and even helping to reduce the risk of electrostatic in the tank.

Pros /Cons
  • Suitable for a wide range of engines, regardless of their materials and functions
  • Active lubrication of pumps and piping
  • Minimal risk of blockage
  • Reduce internal static electricity
  • Impact lasts about 2-3 years
  • Not suitable for large leaks

4. Prestone Radiator Stop Leak

Prestone Radiator Stop Leak

If you want to find a product and stop leaking fast, then the Preston radiator stop leaking won’t disappoint you.

This radiator leak sealant is designed using a patented formula that works very quickly.

When stopping radiators, pumps and heater cores from leaking.

Another benefit of this product is that it will also protect your vehicle from pitting and corrosion.

It is made from an effective mixture of natural fibers and synthetic fibers.

Actually it uses the same material found in the bulletproof vest, so with this product, you definitely get some serious tough material!

Although the product seal leaks, you don’t have to worry about it will clogging the radiator or heater core tube.

Pros /Cons
  • Designed with a patented formula
  • Protect your vehicle from pitting and corrosion
  • Can easily seal leaks up to 0.020 inches x 0.5 inches
  • Not suitable for larger system problems

5. Genuine GM Fluid 3634621 Cooling System Seal Tablet

Genuine GM Fluid 3634621 Cooling System Seal Tablet

When choosing a simple fixture for a cooling radiator system, there is no solution to use the original GM seal without any effort.

Whether you have trucks, cars, motorcycles, off-road vehicles or anything in between.

These non-toxic tablets are compatible with a wide range of vehicles.

They are even compatible with the DEX-COOL system, ensuring that there is no need to worry about quality.

Although these tablets are not suitable for greater damage, such as gasket blowouts, any pinholes or small sized holes.

Your radiator system will be repaired in one instance by general wear shrinkage, ensuring that your vehicle can continue to operate.

Buying five tablets at an affordable price, which may be the simple answer you’ve been looking for.

Pros /Cons
  • Five packs for multiple purposes
  • Compatible with various radiator / cooling systems
  • Suitable for small holes
  • Not suitable for large damage

Benefits of Radiator Stop Leak

  • Prevent a breakdown: Driving with a radiator leak is incredibly harmful to your vehicle. Any major loss of radiator fluid will likely cause your car to break down, leaving you stranded on the side of the road. The radiator works by cooling down the vehicle’s engine with the use of liquid coolant. The hotter the engine gets, the higher the chance it will overheat, causing a breakdown.
  • Improve performance: Checking to make sure the radiator stop leak is constantly getting fluid will help keep the car running properly. Over time, a leak will wear down your car’s power and could damage other parts of the vehicle.
  • Protect seals: Hardened or dried seals cause most oil leaks. Oil leak additives work by revitalizing the main seal and head gaskets to return to their original size and flexibility. This reduces the amount of oil that is capable of seeping through.

How to Use Radiator Stop Leak

Once you’ve come to the conclusion that you need a radiator stop leak product for your leaking radiator or gasket, then you are going to want to keep a few things in mind from buying the product all the way to using the product. Below are some of the steps required to use these products well and use them in a way that’s beneficial to your vehicle and actually stops the leaks in question.

  • Purchase the Appropriate Sealant: The first thing that you are going to want to do is find the best radiator sealant possible. This means one that not only meets quality standards but is designed for the vehicle you’re using it on.
  • Read Product’s Directions: It’s extremely important to read ALL of the directions included with your sealant. And you should not only read them but follow them exclusively. If the directions happen to disagree with any of our suggestions, then disregard what we have written here and follow the package’s directions.
  • Pour It Into The Radiator: Make sure that your product doesn’t require the radiator to be drained or flushed before it’s used. If it does, then that will need to be done before continuing.
  • Start the Car: Most of the sealant products on the market require the car to be idled or driven for 15 to 20-minutes before the product is able to work. So, start the car and allow the engine to warm up.
  • Allow The Car To Sit Overnight: One of the reasons many radiator stop leak repair jobs fail is that some people fail to let their car sit for the appropriate time.