Best Radiator Flush: Keep Your Radiator Running Clean

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

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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
    Prestone AS105 Radiator Flush and Cleaner
    Prestone’s radiator flush provides a heavy-duty cleaning to your entire cooling system. It can help restore engine efficiency by removing heavy deposits.
    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.
    It can take a couple of 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.
  • Best Value
    Irontite ThoroFlush
    Irontite ThoroFlush is an industrial strength radiator cleaning agent. It will help to open clogged heater cores and flush out the old coolant from your cooling system.
    This flush can help to remove rust, scale, grease, oil, and sludge from your radiator. Just one pint can flush blockage out of the cooling system. It is a powerful powder flush that you dilute.
    If left in too long, this product can be corrosive to many metals. It is only safe to use on cast iron, aluminum or plastic. It can also cause skin or eye irritation if proper safety measures are not used.
  • Honorable Mention
    Gunk Motor Medic 10-Minute Radiator Flush
    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.
    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.
    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.

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 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.


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 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 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 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 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


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.


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 2019

Best Radiator Flush Overall: Prestone AS105 Radiator Flush and Cleaner

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.

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Best Radiator Flush Value: 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.

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Best Radiator Flush Honorable Mention: Gunk Motor Medic 10-Minute Radiator Flush

Gunk Motor Medic 10-Minute Radiator Flush

Last but certainly not least, 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. Moreover, a 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 that 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.

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  • 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.


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 Prestone AS105 Radiator Flush and Cleaner. 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 of bucks but still use a high-quality product, try Irontite ThoroFlush.

Have you recently flushed your radiator? Leave a comment telling us what products and methods you prefer.