Best Radiator Stop Leaks

A radiator stop leak is a sealant product that is used to repair and stop leaks in the vehicle radiator and cooling system.

In some cases the use of this product provides a temporary solution to the issue, however many radiator stop leak products help to ensure that your vehicle is performing at its best, providing a cost-effective and minimal time consuming solution to leaks.

For those who are unfamiliar with using this type of product, you may be a little puzzled in regards to how they are intended to be used.

While many vehicle owners avoid using a radiator stop leak for fear that it may lead to potential damage, when used correctly and in accordance with the guidelines, they can be an effective solution.

We have taken the hard work out of the process and picked our top five choices of the best products on the market.

If you remain uncertain as to what you should be considering before making your purchase, below you will find a buyer’s guide where we have identified some useful tips for selecting the best product.

If you are in a hurry and don’t have the time to continue reading, we have selected our top pick for you below.


[amazon fields=”B002696FA2″ value=”thumb”]

Bar’s Leaks Liquid Aluminum Stop Leak


[amazon fields=”B002BJEG3U” value=”thumb”]

K-SEALANT Coolant Leak Repair


[amazon fields=”B002PX91OG” value=”thumb”]

Bar’s Leaks Intake and Radiator Stop Leak


Bar’s Leaks Liquid Aluminum Stop Leak

[amazon fields=”B002696FA2″ value=”thumb” image_size=”large”]

The Bar’s Leaks Liquid Aluminum Stop Leak isn’t only suitable for repairing radiator leaks but also gasket leaks, freeze plug leaks and heater core leaks.

This product works by lowering the temperature and it can be applied directly to your cooling system without needing to be flushed.

Using this product is also particularly straightforward and instantly seals the leaks. Despite this, it is advised that you leave the vehicle for roughly 20 minutes to give the product plenty of time to dry before you begin using your vehicle again.

A reliable solution that performs fast for effective results, the Bar’s Leaks Liquid Aluminum Stop Leak is compatible with all types of coolants whether they are yellow, orange, pink, red, blue, or green.

Not only does this stop leak do an excellent job of sealing any leaks, but it also ensures that your system is in tip-top condition too.


  • This stop leak product is super versatile and can be used to repair a variety of different likes.
  • This product has been made in the USA so you are aware of where it has been purchased.
  • It is compatible for use with all coolants.
  • It retails at an affordable price and therefore provides a cost-effective solution to repairing leaks.
  • Bar’s Leaks is a brand that is renowned for producing quality products so you can be confident in your purchase.


  • While this product works in smaller leaks, it may not be as effective in dealing with larger leaks.


K-SEALANT Coolant Leak Repair

[amazon fields=”B002BJEG3U” value=”thumb” image_size=”large”]

If you’re looking for a fast performing product that is going to seal leaks within minutes, look no further than the K-SEALANT Coolant Leak Repair.

As a versatile product, it is suitable for use in tackling a range of different problems including leaking radiators, leaking freeze plugs, head gasket repairs, or heater core and water pump repairs.

The Unique microfiber formula will permanently seal any radiator leaks soon after contact. It has also been scientifically tested and is proven to be safe and effective in repairing leaks measuring up to 1/32 of an inch.

Once cured, it doesn’t pose any risk of the cooling system failing or clogging.

Courtesy of the pour and go bottle design, this product is easy to use. It simply needs to be added to the radiator before running the engine. Impressively, it doesn’t require flushing or draining either.


  • It is compatible with all antifreeze.
  • As a versatile product, it can be used to repair a range of leaks.
  • The pour and go bottle design allows for easy use.
  • This is a great permanent solution for repairing leaks.
  • Once it has been added, it doesn’t require flushing or draining.



Bar’s Leaks Intake and Radiator Stop Leak

[amazon fields=”B002PX91OG” value=”thumb” image_size=”large”]

The Bar’s Leaks Intake and Radiator Stop Leak can be used to repair larger sized radiator leaks as well as heater core leaks, freeze plug leaks, blown head gaskets and it can also be used to repair blocks.

This one-step formula contains sodium silicate which is compatible with antifreeze so you aren’t required to drain the cooling system beforehand.

Using the product is pretty simple so long as the manufacturer’s guidance is adhered to. The product can be used in water alone, however, it is recommended that you add a second bottle of Liquid Copper to the system following the installation of the antifreeze.

Coming in an 18oz bottle, you have a sufficient amount of products for engines that range from 4-8 cylinders.

Once added to the system, it is also likely to offer a lengthy solution before the leaks require further repair.


  • Affordably priced, this product offers a great value option for sealing leaks.
  • It is available in a singular pack or 6 pack so you can select the quantity required for your needs.
  • It can be used to repair many leaks, as well as blown head gaskets and blocks.
  • As a one step solution, this radiator stop leak is easy to use.
  • Courtesy of the formula content it is compatible with most antifreeze.


  • This product is a great temporary solution but isn’t as effective in the long run for repairing leaks.


AlumAseal Radiator Stop Leak Powder

[amazon fields=”B000FW61M4″ value=”thumb” image_size=”large”]

AlumAseal is a powder formula solution that works to stop radiator leaks without causing your cooling system to become clogged.

For those that are looking for a quick but effective solution, this product could be an excellent choice.

A great thing about the AlumAseal Radiator Stop Leak Powder is it is safe to be used on all metal, plastic, and rubber cooling system parts and is also compatible with all antifreeze and coolants. This makes it an effective product for the majority of vehicle owners.

Additionally, this stop leak powder also helps to prevent the development of rust to ensure that the cooling system maintains great quality.

Using this product is very straightforward. The powder simply needs to be poured into the radiator before allowing the engine to run for a decent amount of time.

It is also effective in treating cooling systems measuring up to 21 liters.


  • This is a convenient product that is safe to use.
  • It is suitable for use on all types of metal, plastic, and rubber.
  • It isn’t going to cause the cooling system to become clogged after use.
  • It retails at an affordable price providing a great value option.
  • It is compatible with all types of antifreeze and coolants.


  • This product doesn’t completely stop the leaks although it is an effective temporary solution.


Liqui Moly Radiator Stop Leak

[amazon fields=”B076ZP45Z5″ value=”thumb” image_size=”large”]

The Liqui Moly Radiator Stop Leak is ideal for repairing small leaks, in particular, providing an immediate solution.

Straightforward to use, this stop leak works to secure the combustion chamber by preventing the coolant from becoming contaminated.

It can be used on all cooling and heating systems regardless of whether they have water filters and is suitable for treating up to 10 liters of coolant.

To use the product, you simply need to shake it before use before adding it to the cooling system and then starting the heater.

After doing so, it is then recommended that you drive your vehicle for roughly 10 minutes.

Although this product has been made in Germany, it is suitable for use on many vehicles working to deliver fast and noticeable results.


  • This product intends to seal small leaks and cracks.
  • It works effectively in sealing any leaks that are present in the radiator.
  • It is fast and easy to use and works to deliver immediate results.
  • It is suitable for use on all cooling and heating systems.
  • It isn’t going to cause the system to become clogged and prevents engine contamination.


  • Similar to many other products, this product may not be effective in solving all types of leaks.

Best Radiator Stop Leaks Buying Guide

There are many variations of radiator stop leak products available on the market, for this reason, it is important to consider many factors before making your purchase.

This is of particular importance if you are unfamiliar with this type of product and how it is intended to be used.

Below, we have identified our top tips for selecting the right product.

Vehicle Compatibility

Before making your purchase it is important to consider the compatibility with your vehicle.

Choosing a product that is incompatible with your vehicle radiator can cause the engine to become damaged as a result.

The specifications of the product will state the vehicle compatibility and this will allow you to select the product according to this.

Paying close attention to this factor helps to avoid the occurrence of potential damage.

The Performance

If you are currently experiencing a radiator leak, you want to attempt to repair it as soon as possible.

Sealing a radiator leak using a stop leak product can rectify this issue before it evolves into a more severe issue that could soon result in a costly expense.

Ideally, your product should be fast-acting as this is going to make it more effective in fixing any leaks before they become more severe.

Using the Product

If you are unfamiliar with this kind of product, using it for the first time may appear daunting, particularly if you are a little cautious about causing damage to your vehicle.

While many individuals may choose to go to a mechanic to apply the stop leak product, others may be a little more confident in using the product themselves.

In general, most stop leak products are easy to use and tend to come with guidance regarding how the product should be used.

The Severity of the Leak

A leaking radiator can differ in severity depending on when it is discovered.

If you spot the leak in the early stages it isn’t likely to be as severe, however, a larger sized leak can become difficult to repair and so you may find yourself looking for professional mechanical guidance.

If possible, you should try to seal the leak as soon as possible so that it doesn’t have the time to worsen and develop into a more severe issue.

The Type of Product

Radiator stop leak products are available in two different forms. The most popular type tends to be a liquid-based product.

A product of this kind tends to flow through the engine with greater ease and viscosity and can help to combat rust while helping to break down the build-up of dirt and grime.

The other form of this product is a radiator stop leak tablet that dissolves following contact with the fluids. Once the temperature has exceeded a particular degree the particles will then burn and work to seal the cracks of the radiator.

The Brand  

You will find that they are many dominant brands within this industry.

Many of these brands are renowned for creating excellent quality products that are effective in serving their purpose of repairing any leaks. For this reason, you may develop confidence in one brand in particular.

While it is necessary to note that these brands produce great quality products, many other brands produce excellent quality products too.

The Chemical Contents

Before using a radiator stop leak, it is necessary to pay attention to the contents of the product.

Some products will contain a varied amount of chemical compounds that can cause potential issues with the antifreeze or may also cause the engine to become damaged.

The Size of the Product

It is also necessary to consider the frequency in which you require the use of this product.

You will find that products of this kind are available in various quantities. The amount of product that you require is going to depend on the leaks that you are dealing with. If you are dealing with a larger leak you are likely to need more products.

However, if you often find that your radiator is subject to a smaller leak you may not need to purchase as much product. It is also dependent on the quality of the product. If the stop leak does an insufficient job in sealing the leak, you are likely to require more use of the product.

The Cost

Most radiator stop leak products retail within an affordable price range, therefore providing a cost-effective solution to an issue that can soon become pretty expensive if it isn’t dealt with before developing into one that’s more severe.

There is a risk of compromising on the quality if you opt for a cheaper priced product. While you don’t necessarily need to break the bank when investing in your product, it is necessary to consider how well the product performs.


You will find many products that are deemed to be permanent solutions, however, they don’t fulfill their purpose in repairing your leaks for long term effectiveness.

The majority of radiator stop leak products are likely going to provide you with a temporary solution before needing to be repaired again further down the line.

Although your stop leak product may only be a temporary fix, it is likely to last for a decent amount of miles before beginning to deteriorate and causing the leak to worsen again.

Therefore, when choosing your product, it is necessary to be aware of this so that you can be prepared for possible repairs in the future.

Suitability for Antifreeze and Coolant

The specifications of your product will state whether it is compatible with particular types of antifreeze and coolant.

The majority will be suitable for all types, however, it is important to check this beforehand to ensure that it is otherwise the stop leak product may cause the cooling system to become damaged.

Frequently Asked Questions

Is a radiator stop leak safe to use?

If the instructions of the product are followed correctly a stop leak product doesn’t pose a risk of damage.

However, if you fail to adhere to the instructions, then yes there is the risk of the product causing damage to your vehicle’s cooling system.

How long does it take for a radiator stop leak to work?

After using a stop leak product on your vehicle, it is advised that you wait for around 15 to 30 minutes before using your vehicle.

It is highly likely that the sealant will be sealed following this time, however, if it isn’t you may need to apply a second layer and then wait for this to apply before using your vehicle.

Some products may require you to use the vehicle for a few minutes to seal the product.

Is a radiator stop leak product actually going to work?

Many factors can influence how well your product is going to work.

The quality of the product is going to determine how effective your stop leak product is.

Some products may be ineffective in providing a long term solution but more effective in providing a short term solution.