Reviews

LAST UPDATED: May 8, 2019

Best Radiator Flush: Keep Your Radiator Running Clean

Lengthen the life of your car with these top radiator flush products

Entering our 7th season of /DRIVE on NBC Sports, and with millions of YouTube and Facebook followers, The Drive is a leading authority of all things automotive.

The Drive on NBCThe Drive on YouTubeThe Drive on Facebook

The Review Team

  • Product Network

    20 Products

  • Clock

    12 Hours

  • Reviews

    9 Reviews

How We Decided

The Drive and its partners may earn a commission if you purchase a product through one of our links.Read more.

PUBLISHED ON May 8, 2019

Your car’s radiator is one of the most important parts of its system. The radiator transports coolant to the engine to keep the engine from overheating. If your radiator is clogged, it will not work properly and could lead to your engine overheating. To keep your radiator running clean and smooth, it should be flushed regularly. In this article, you will find our recommendations and reviews for the best radiator flush solutions and how to properly flush your radiator.

  • Best Overall
    Thermocure Coolant System Rust Remover
    Thermocure Coolant System Rust Remover
    Summary
    Summary
    This is a multipurpose additive that works to condition the engine system by removing rust and deposits from the radiator, water pumps, and the engine block.
    Pros
    Pros
    It’s a non-corrosive and biodegradable formula that’s safe on metal, rubber, plastics, and other surfaces. It prolongs the engine life and helps it to run cooler. Effective at removing grime and heavy deposits.
    Cons
    Cons
    The fluid emits strong fumes with an unpleasant smell. It can turn to gel if left in the cooling system for a long time. Not the best cooling agent. 
  • Best Overall
    Thermocure Coolant System Rust Remover
    Thermocure Coolant System Rust Remover
  • Best Value
    Gunk Motor Medic 10-Minute Radiator Flush
    Gunk Motor Medic 10-Minute Radiator Flush
    Summary
    Summary
    Gunk Motor Medic 10-Minute Radiator Flush helps to remove the blockage from your engine’s cooling system. It can help your engine run smoother and longer without overheating.
    Pros
    Pros
    This is a radiator flush chemical that is a non-acidic product that is an easy, one-step process. It is compatible with all cooling systems and removes grease, scum, rust, and scale.
    Cons
    Cons
    It works best if left in longer than what the directions state. You may need to use it a few times before the flush will be completely clear. It also may not be eco-friendly when it is flushed from the radiator.
  • Best Value
    Gunk Motor Medic 10-Minute Radiator Flush
    Gunk Motor Medic 10-Minute Radiator Flush
  • Honorable Mention
    Prestone AS105 Radiator Flush and Cleaner
    Prestone AS105 Radiator Flush and Cleaner
    Summary
    Summary
    Prestone’s radiator flush provides a heavy-duty cleaning to your entire cooling system. It can help restore engine efficiency by removing heavy deposits.
    Pros
    Pros
    This radiator coolant flush is non-toxic and non-acidic. It helps prevent your engine from overheating and is safe to use on all cooling system metals.
    Cons
    Cons
    It can take a couple times of repeating the entire process to get a thorough flush. This product is also non-toxic, but still has harsh chemicals that could have runoff that is not eco-friendly.
  • Honorable Mention
    Prestone AS105 Radiator Flush and Cleaner
    Prestone AS105 Radiator Flush and Cleaner

    Your car’s radiator is one of the most important parts of its system. The radiator transports coolant to the engine to keep the engine from overheating. If your radiator is clogged, it will not work properly and could lead to your engine overheating. To keep your radiator running clean and smooth, it should be flushed regularly. In this article, you will find our recommendations and reviews for the best radiator flush solutions and how to properly flush your radiator.

    Best Radiator Flush Reviews & Recommendations 2020

    Best Overall

    Thermocure is a non-toxic and biodegradable formula that’s designed for professional and personal use. Once flushed into the cooling system, this fluid removes rust deposits and scales from the radiator, water jackets, water pumps, engine blocks, and heads. 


    It restores the engine’s ability to transfer heat to the cooling system and consequently makes it last longer. You will notice at least a 10 degree Fahrenheit temperature reduction, which is enough to boost engine performance. It’s estimated that one 32-ounce bottle can treat up to a three-gallon tank.  


    However, you may want to keep your face away from the bottle once you open it. It emits strong fumes with an unpleasant odor. Also, it’s cooling effect on the engine isn’t as long-lasting as most dedicated cooling additives on the market. In addition, the fluid can turn into gel when not flushed out in good time.

    Best Value

    The Gunk Motor Medic Radiator Flush is a strong solution for clogged radiators. The name says the flush only takes 10 minutes, but this of course depends on the severity of the clog. More severe blockage may take longer to flush.


    The benefit to this solution is that it is a one-step process, so all you have to do is pour it in and flush it out with water. The solution comes ready to use, so you don’t have to worry about diluting or mixing anything. Depending on how severe the blockage is, you may need to repeat the process a few times to make sure everything that blocked the radiator system is clear.


    The only reason this product didn’t rank higher is because one bottle may not be enough to completely flush a dirty radiator. It may take a few times and more than one bottle to completely get the job done.

    Honorable Mention

    Prestone Radiator Flush and Cleaner made our top product list because it is easy to use and effective. This product will remove a heavy blockage from your cooling system without the use of acidic or damaging chemicals.


    This product works quickly. Although the directions do state to pour it in and flush it out after only a few minutes, it is actually much more effective to leave it in and go about your normal routine for the day. Then at the end of the day, flush the system with clean tap water until it runs clear.


    The downside to this is that it takes a little more time to work than the directions say. Plus, leaving this product in too long or forgetting that you put it in can be potentially damaging to your car. The plus side is that it’s non-toxic and non-acidic so it would take much longer to do severe damage.

    Honorable Mention

    Irontite ThoroFlush is a highly-concentrated powder chemical. When diluted properly, it provides a powerful cleaning that can help remove stubborn grease, scale, and other blockages from the radiator.


    To use this product, it is essential that the powder is mixed well in a container that will be easy to pour. Once the solution is ready, it can be poured in and flushed out in just minutes. You may want to repeat all of the steps a few times to ensure a thorough flush.


    Unfortunately, the powder can be difficult to use and can be a health hazard. If the powder is ingested or sticks to the skin, its strong properties can cause chemical burns. Use proper protective clothing when using powder radiator flush products like this one. This product can also be damaging to your car if you leave it in too long, so pay close attention to the directions including using distilled water if you desire.

    Honorable Mention

    As the name suggests, it only takes 10 minutes for this liquid flush to burst into action. It works on the cooling system to remove rust and deposits, and flush out oil and other pollutants from the engine system. It’s compatible with almost all cooling systems including aluminum and plastic radiators.


    This flush is non-toxic, safe, and doesn’t require neutralization. Use it every time you change the coolant to get the best results. It’s a great choice for anyone looking for the perfect balance of value and convenience, since it's a reasonably priced flush that will suit your cooling system’s needs. 


    However, the cleaning results pale in comparison to what high-end cleaners can do. It also needs to be thoroughly flushed out of the system. Otherwise, you will end up with white soapy residue in the radiator.

    Honorable Mention

    The Valvoline Radiator Flush is typically used to flush out corroded sediments, oily residue, scale, and rust from the radiator. The flush takes less than 10 minutes to dissolve the thick deposits in the engine, after which it will turn muddy. You should then drain it out for the engine to function optimally. 


    It’s safe to use this fluid on aluminum, iron, brass, and plastic radiators. What’s more, it can help clean out clogged heater cores and flush out other contaminants with a single treatment. However, some users didn’t see any results. Therefore, you may want to use a stronger cleaner to remove heavy corroded deposits from the radiator.

    Honorable Mention

    Liqui Moly is a well-respected automotive brand, and this product is no exception. The Liqui Moly Radiator Cleaner is formulated to deep clean and protect your cooling system. It’s recommended for all motor vehicles including ones that have rubber and plastic radiators.  


    Liqui Moly includes active cleaning agents that disperse all solid deposits and sludge that are lodged on the radiator wall. The fluid works to dissolve contaminants such as oil and lime deposits that prevent the engine from achieving its optimal operating temperature. It goes further to neutralize harmful acids or alkalis in the cooling system. 


    However, considering that you have to flush out the dirt, you may find that one 10-ounce bottle isn't enough for repeated use. Also, some users didn’t find the process very easy.

    Honorable Mention

    For a versatile and reasonably priced cleaning fluid, we recommend the BlueDevil Radiator Flush. It works well on almost all vehicles. It’s easy to use and features an advanced cleaning power, which removes rust, grime, grease, and other deposits that result from normal vehicle operations. From the protection level it offers, it has been noted that the product will reduce the failing chances of your pump gaskets and seals. 


    This blue fluid is ideal for all vehicles, and ensures that the coolant levels don’t drop even after months of a single treatment. Moreover, it’s specially formulated for high mileage vehicles to improve engine performance. 


    However, it may be a letdown for removing mineral and corroded deposits that are common in such vehicles. Some users had gelling issues.

    Honorable Mention

    This heavy-duty radiator flush can be used safely with aluminum and other cooling system metals and is designed to remove deposits such as solder bloom, rust, and scale. It works with all antifreeze coolants and reduces temperatures on cooling systems that have plugged radiator tubes and passages.


    This product removes a surprising amount of gunk. Its formula cleans, seals, and protects the cooling system. Zerex Super Radiator Cleaner cleans a vehicle's cooling system more thoroughly than its other product, Zerex Super Flush.


    One downside is you may need more than one bottle in order to get the results you require. Also, it works best if you use distilled/deionized water or a pre-diluted coolant for the final refill of your cooling system. In addition, since it's a cleaner, it does not provide freeze or boiling protection. 

    Why Trust Us


    All of our reviews are based on market research, expert input, or practical experience with most products we include. This way, we offer genuine, accurate guides to help you find the best picks.

    Learn more

    Benefits of Radiator Flush

    • Keep your cooling system running properly. Your coolant system can easily become clogged by scale, grease buildup, and other debris that gets into the system. Using the best cooling system flush for your radiator can help remove these obstacles to keep the system running properly.
    • Help improve engine efficiency. Your radiator pumps coolant into your car’s engine, keeping it cool and preventing it from overheating. Without it, your engine would suffer and work much harder than it should. Radiator flush can help prevent debris from clogging your engine. Much like a person who has been running for a long time in heat needs their body to cool itself by sweating and pumping blood through your heart, your car’s engine needs its radiator to help keep it cool.
    • Lengthen the life of your vehicle. Letting your car run for years and years without flushing your radiator can allow buildup and blockage to take place. By cleaning your clogged radiator, you can help lengthen the life of your car by keeping the engine and cooling system running clean.

    Types of Radiator Flushes

    Liquid

    Liquid radiator flushes are the most common, and arguably the best radiator flushes.These solutions are simply poured in and flushed out, typically with water, to clean your clogged radiator.

    Powder

    Although powder radiator flushing chemicals are less common, they are still very effective. The powder solutions need to be diluted before using, creating an extra step for the user. The powder itself is highly concentrated and could be damaging if not diluted properly.

    Top Brands

    Prestone

    Prestone is one of the most well-known companies for its automotive products. It produces high-quality cleaning solutions that are staples for any car owner to have handy, including oil change products. One of Prestone’s most common and popular products is their Super Radiator Flush, which is very affordable and effective.

    IronTite

    IronTite is a smaller company that provides limited yet effective products for engine maintenance. It has several different options for flushes and seals that all work well to keep cars running well. Its most common product is the All Weather Seal which helps stop leaks in your cooling system.

    Gunk

    Gunk is a family-operated company based in Charlotte, North Carolina. This company has made quality automotive products for over 75 years and continues to be a popular choice among DIYers. One of their most popular product is their Super Heavy Duty Radiator Flush which helps to remove dirt and grime from engines.

    Evaporust

    Evaporust is another top brand for automotive products, including radiator flush. This company is known for its non-toxic, biodegradable products that are safe on skin and eyes. It has many different products for all areas of your car, but the most common is their Thermocure Coolant System Rust Remover, which cuts through damaging rust to keep your cooling system clean.

    Radiator Flush Pricing

    • $20 or less: This price range includes some of the less concentrated solutions but is still effective. These solutions may have less of the active ingredients that you would find in a more expensive brand, which means you would most likely need to use more of the product for it to be as effective. You may also find that radiator flushes in this price range come in smaller amounts.
    • $20-$40: This is the most common price range you will find for a radiator flush. You will most likely get just the cleaning solution itself in a container around 22 ounces.

    Key Features

    Potency

    Some of these products are more concentrated than others. The more potent the solution is, the more cleaning power it will have. This can be both good and bad, however, because although a powerful clean is important, too powerful can damage the metal in your car.

    Form

    Radiator flushes come in different forms, including the premixed liquid that is ready to use and powder form that you have to dilute before using. Each form has its benefits, but directions should be followed to be used correctly. The powder solutions need to be mixed and diluted properly to be most effective, but you can expect them to be very concentrated and powerful. The liquid solutions are much easier to use since they involve fewer steps, but you may have to use it multiple times for it to work thoroughly.

    Other Considerations

    • Time. While these products all have instructions on how to use them, you may find that trial and error might be better to get the best results and it might not happen as fast as the directions say. The best way to flush a radiator depends on how severe the blockage is and what kind of materials your cooling system consists of. It may take longer to flush a severely clogged system than it would flush one that has an only minor blockage. 
    • Compatibility. One of the most important things to research to properly flush your radiator is whether or not it is compatible with the type of metal or plastic in your car. Certain flushes are not meant to be used on certain metals and can actually do more harm than good because of their corrosive capabilities.
    • Safety. As stated earlier, these chemicals have extremely corrosive qualities that can be dangerous. You should always wear protective gloves and glasses when using these products to prevent chemical burns.

    Best Radiator Flush Reviews & Recommendations 2020

    Best Overall
    Thermocure Coolant System Rust Remover

    Thermocure is a non-toxic and biodegradable formula that’s designed for professional and personal use. Once flushed into the cooling system, this fluid removes rust deposits and scales from the radiator, water jackets, water pumps, engine blocks, and heads. 


    It restores the engine’s ability to transfer heat to the cooling system and consequently makes it last longer. You will notice at least a 10 degree Fahrenheit temperature reduction, which is enough to boost engine performance. It’s estimated that one 32-ounce bottle can treat up to a three-gallon tank.  


    However, you may want to keep your face away from the bottle once you open it. It emits strong fumes with an unpleasant odor. Also, it’s cooling effect on the engine isn’t as long-lasting as most dedicated cooling additives on the market. In addition, the fluid can turn into gel when not flushed out in good time.

    Best Value
    Gunk Motor Medic 10-Minute Radiator Flush

    The Gunk Motor Medic Radiator Flush is a strong solution for clogged radiators. The name says the flush only takes 10 minutes, but this of course depends on the severity of the clog. More severe blockage may take longer to flush.


    The benefit to this solution is that it is a one-step process, so all you have to do is pour it in and flush it out with water. The solution comes ready to use, so you don’t have to worry about diluting or mixing anything. Depending on how severe the blockage is, you may need to repeat the process a few times to make sure everything that blocked the radiator system is clear.


    The only reason this product didn’t rank higher is because one bottle may not be enough to completely flush a dirty radiator. It may take a few times and more than one bottle to completely get the job done.

    Honorable Mention
    Prestone AS105 Radiator Flush and Cleaner

    Prestone Radiator Flush and Cleaner made our top product list because it is easy to use and effective. This product will remove a heavy blockage from your cooling system without the use of acidic or damaging chemicals.


    This product works quickly. Although the directions do state to pour it in and flush it out after only a few minutes, it is actually much more effective to leave it in and go about your normal routine for the day. Then at the end of the day, flush the system with clean tap water until it runs clear.


    The downside to this is that it takes a little more time to work than the directions say. Plus, leaving this product in too long or forgetting that you put it in can be potentially damaging to your car. The plus side is that it’s non-toxic and non-acidic so it would take much longer to do severe damage.

    Honorable Mention
    Irontite ThoroFlush

    Irontite ThoroFlush is a highly-concentrated powder chemical. When diluted properly, it provides a powerful cleaning that can help remove stubborn grease, scale, and other blockages from the radiator.


    To use this product, it is essential that the powder is mixed well in a container that will be easy to pour. Once the solution is ready, it can be poured in and flushed out in just minutes. You may want to repeat all of the steps a few times to ensure a thorough flush.


    Unfortunately, the powder can be difficult to use and can be a health hazard. If the powder is ingested or sticks to the skin, its strong properties can cause chemical burns. Use proper protective clothing when using powder radiator flush products like this one. This product can also be damaging to your car if you leave it in too long, so pay close attention to the directions including using distilled water if you desire.

    Honorable Mention
    Bar’s Leaks 10-Minute Flush

    As the name suggests, it only takes 10 minutes for this liquid flush to burst into action. It works on the cooling system to remove rust and deposits, and flush out oil and other pollutants from the engine system. It’s compatible with almost all cooling systems including aluminum and plastic radiators.


    This flush is non-toxic, safe, and doesn’t require neutralization. Use it every time you change the coolant to get the best results. It’s a great choice for anyone looking for the perfect balance of value and convenience, since it's a reasonably priced flush that will suit your cooling system’s needs. 


    However, the cleaning results pale in comparison to what high-end cleaners can do. It also needs to be thoroughly flushed out of the system. Otherwise, you will end up with white soapy residue in the radiator.

    Honorable Mention
    Valvoline ZXC01 Radiator Flush

    The Valvoline Radiator Flush is typically used to flush out corroded sediments, oily residue, scale, and rust from the radiator. The flush takes less than 10 minutes to dissolve the thick deposits in the engine, after which it will turn muddy. You should then drain it out for the engine to function optimally. 


    It’s safe to use this fluid on aluminum, iron, brass, and plastic radiators. What’s more, it can help clean out clogged heater cores and flush out other contaminants with a single treatment. However, some users didn’t see any results. Therefore, you may want to use a stronger cleaner to remove heavy corroded deposits from the radiator.

    Honorable Mention
    Liqui Moly Radiator Cleaner

    Liqui Moly is a well-respected automotive brand, and this product is no exception. The Liqui Moly Radiator Cleaner is formulated to deep clean and protect your cooling system. It’s recommended for all motor vehicles including ones that have rubber and plastic radiators.  


    Liqui Moly includes active cleaning agents that disperse all solid deposits and sludge that are lodged on the radiator wall. The fluid works to dissolve contaminants such as oil and lime deposits that prevent the engine from achieving its optimal operating temperature. It goes further to neutralize harmful acids or alkalis in the cooling system. 


    However, considering that you have to flush out the dirt, you may find that one 10-ounce bottle isn't enough for repeated use. Also, some users didn’t find the process very easy.

    Honorable Mention
    BlueDevil Radiator Flush

    For a versatile and reasonably priced cleaning fluid, we recommend the BlueDevil Radiator Flush. It works well on almost all vehicles. It’s easy to use and features an advanced cleaning power, which removes rust, grime, grease, and other deposits that result from normal vehicle operations. From the protection level it offers, it has been noted that the product will reduce the failing chances of your pump gaskets and seals. 


    This blue fluid is ideal for all vehicles, and ensures that the coolant levels don’t drop even after months of a single treatment. Moreover, it’s specially formulated for high mileage vehicles to improve engine performance. 


    However, it may be a letdown for removing mineral and corroded deposits that are common in such vehicles. Some users had gelling issues.

    Honorable Mention
    Zerex Super Radiator Cleaner

    This heavy-duty radiator flush can be used safely with aluminum and other cooling system metals and is designed to remove deposits such as solder bloom, rust, and scale. It works with all antifreeze coolants and reduces temperatures on cooling systems that have plugged radiator tubes and passages.


    This product removes a surprising amount of gunk. Its formula cleans, seals, and protects the cooling system. Zerex Super Radiator Cleaner cleans a vehicle's cooling system more thoroughly than its other product, Zerex Super Flush.


    One downside is you may need more than one bottle in order to get the results you require. Also, it works best if you use distilled/deionized water or a pre-diluted coolant for the final refill of your cooling system. In addition, since it's a cleaner, it does not provide freeze or boiling protection. 

    Tips

    • Remove the radiator drain plug carefully. The radiator drain will allow the old coolant to quickly and easily leave the vehicle.
    • Make sure you are flushing your radiator responsibly. Try to avoid flushing out your old antifreeze near bodies of water that may be drinking sources for wildlife. If possible, drain the solution into a proper container and dispose of it responsibly to protect the environment.
    • Check your coolant level. Remove the radiator cap and ensure that your vehicle has the correct amount of coolant after your flush.
    • While these products can be very effective in cleaning your radiator, they are not miracle workers. If your engine is suffering from severe damage, simply flushing your radiator might not be enough to solve the problem. If you are still experiencing problems after you have finished your engine flush, consider getting it looked at by a professional mechanic.

    FAQs

    Q: How will I know if the engine flush worked?

    A: Once you have flushed your radiator, you should be able to tell if the clean water you are pumping through the system is coming out clear or muddled. If it is clear, it is a sign that the flush worked and there is no longer a blockage in your radiator, Otherwise, you may need to keep adding solution and flushing it out until there are no signs of debris.

    Q: How long does it take to flush a radiator?

    A: This will depend on the severity of the blockage and the strength of the solution. Typically, it is best to let a liquid solution sit in your system throughout the day as you drive your normal routes. Then, flushing the fluid should only take a few minutes. If you are using a more concentrated powder like the IronTite, you will want to pay close attention to the directions because leaving it in too long could cause damage.

    Q: What else do I need to flush my radiator beside the cleaning solution?

    A: You will also need water to flush the solution out of your radiator after you have given it enough time to work. This can be done by pouring water into your radiator, but the easiest and most effective way would be to use a garden hose.

    Q: How do I know when my radiator needs to be flushed?

    A: Depending on the car and how far you are driving, you should only need to flush your radiator once every year or two. However, if you notice your radiator seems to be working poorly or your vehicle frequently becomes overheated, it may be time to flush it.

    Final Thoughts

    Our top choice for radiator flush is the Thermocure Coolant System Rust Remover. With all-around high-quality performance and a reasonable price, in our opinion, it’s one of the best products you can use to flush your radiator.

    If you want to save a couple bucks but still use a high-quality product, try out the Gunk Motor Medic 10-Minute Radiator Flush.