Radiator Stop Leak: Top Products to Protect Your Engine and Keep It Cool
It sounds like magic, but it works and it's remarkable.
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BY Andra DelMonico / LAST UPDATED ON May 12, 2021
You get in your car and back out of your garage or driveway and see an unpleasant sight. There’s that dreaded pool of mystery liquid staring back at you from the ground. You immediately start dreading how expensive the potential repair costs are going to be. That is until you realize that the fluid is coming from your radiator. You breathe a sigh of relief as you realize that this is a leak you can fix at home on your own.
While it may not be a permanent solution, a radiator stop leak is the solution you need to quickly and easily stop your radiator from leaking. Many don’t even require any preparation or special application. You just add it to your vehicle and let it go to work. This guide will help you choose the best radiator stop leak for your vehicle.
It acts as a tight sealer for your cooling system. It is simple to use and can be applied instantly to your radiator. It’s capable of being added to both hot and cold engines.
- Mixes with all types of antifreeze
- Can be left in the cooling system
- Experience leaking again a few weeks or months
The compound works great at sealing leaks but also conditions the engine with liquid aluminum. It is also fitted with an Xtreme Cool formula that stops overheating and reduces water temperature in the radiator.
- Seals leaks in plastic, aluminum, and metal
- Can be added to the cooling system
- Wait up to 20 minutes with the engine idling
- May have to buy in bulk
This copper-colored radiator stop leak is designed for repairing and bonding to automotive, industrial, farm, and marine equipment. It has a liquid glass and copper formula to form a permanent seal.
- 5 minute application time
- Withstands up to 2000 degrees Fahrenheit
- Best for large capacity systems
- Doesn’t dry clear
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Benefits of Radiator Stop Leak
- Prevent a breakdown. When your radiator leaks, it loses fluid, and its ability to keep your engine cool. This allows excessive heat to build up, which can damage your engine. Prolonged exposure to increased temperatures will lead to an eventual breakdown.
- Prolong major repairs. If you aren’t able to take on the expense of a radiator replacement, then a stop leak can be the answer. It will fill the cracks and prevent leaks while you make arrangements for a radiator replacement.
- Extend the life of your car. Older vehicles tend to have more leaks. There’s a point when investing more in a complete radiator replacement isn’t worth it. However, you can’t buy a new car either. Stop leak prolongs the drivable life of your car so that it can keep giving you faithful service
Types of Radiator Stop Leaks
You will see powder stop leaks that come in different formulations and amounts. However, they all generally function the same. Pour the powder into your radiator and let it get to work. This option is simple and easy to use. However, it tends to be less effective than other solutions because you need enough powder to mix in without being so much that it clogs your radiator.
This type of stop leak isn’t a popular one, but you will still be able to find a few options in this form. There are two methods for application. The first is to drop the tablets into your radiator and let them get to work. The other option is to dissolve them in some water and then pour that mixture into your radiator. Once in your radiator, the dissolved particles will heat up and seal the cracks.
Liquid forms of stop sealant are much more common and have a lower viscosity. This makes them move more smoothly through the radiator fluid while also reducing friction. These tend to be made up of additives that help corrode rust and are thicker to fill leaks and reduce dirt and grime.
First founded in California in 1947 by Fred Barton, Bar’s Leaks now calls Holly, Mich., it's home. It makes high-quality stop-leak products for vehicles, including the Bar’s Leaks Liquid Aluminum Stop Leak.
Headquartered in Chicago, Ill., Prestone makes antifreeze, coolants, brake fluids, and power steering products. It’s been in business since 1927 and sells the Prestone Radiator Sealer Stop.
Another recognizable name in automobile parts is ATP. The company started at a Chicago plant in 1955 and it sells transmission parts, filter kits, repair kits, cables, flywheel and ring gears, cabin air filters, chemicals, and much more for your vehicle. The ATP AT-205 Re-Seal Stops Leak is one of its most purchased items.
Radiator Stop Leak Pricing
- $5 to $35: With radiator stop leak fluid, you mainly pay for the size and capacity of the container. Within this price range, you’ll find anything around 12 ounces and below.
- $35 and up: This price range has larger bottles and containers that offer more solution for more applications. It may be best to buy it in bulk to make sure you have extra just in case you run out when you need it most.
Ease of Application
Look for a stop leak that matches your knowledge and skill level. Some require you to flush the entire system before adding the sealant. This may be beyond your skill level or be inconvenient due to the location of the car. If you’re stuck on the side of the road or have little experience with working on your car, then look for one that doesn’t require flushing.
Additives in radiator stop leak fluids work to remove debris, neutralize acidity, and fill leaks. Some stop leak formulas will include additives that protect your system from corrosion and rust. These are a good option if your car is older as they will help preserve your car and run smoother. Other additives help to make the stop leak more durable so that it expands and contracts with the changing temperature of the engine.
Before choosing the best radiator stop leak, you need to read the label carefully. Not all anti-leak fluids will work for every car. Many are specifically designed for certain models like Honda or Ford or engine types such as diesel or gasoline. You should also confirm that the stop leak formula bonds with the material you’re trying to repair. Some bond with several materials, while others are aluminum, steel, or plastic specific.
- Sealing Ability. Look for the dimensions of the leak that the stop leak can clog. Some formulas are more effective and can seal larger leaks. You need a formula that can seal the size of the hole in your cooling system. Most coolants can effectively seal a leak that measures up to .250mm. Anything bigger, and it’s best to seek out a professional repair.
- Antifreeze and Anti-Boil Compatibility. Some stop leaks are not compatible with your antifreeze. These formulas require you to drain the entire system before you add the stop leak. These are tricky to use and can present a risk to your engine.
- Frequency of Use. It is important to consider how frequently you need to use it and its effect on your vehicle in the long run. Keep in mind that fluid can be used multiple times before running out. The more leaks your radiator has, the harder it will be to stop them all.
Best Radiator Stop Leaks Reviews & Recommendations 2021
- Consider the size of the leak in your radiator when adding a stop leak. You may not need very much for small leaks. While larger leaks may require much more. Very large leaks can be too much for the stop leak and will require professional assistance.
- Wear appropriate protective gear while using a stop leak. Be careful not to get it on your skin or in your eyes or mouth. If you do, be sure to follow the safety instructions on the bottle.
- To see if you’ve successfully stopped a leak, leave a piece of cardboard under the car where the fluid usually leaks. After filling the reservoir with stop leak, drive the car around for a bit, and then park it over the cardboard. Check the cardboard to see if any leakage took place.
Q: How long until I see results from a stop leak product?
This can be a difficult question to answer, and it all depends on the type and manufacturer of the stop leak. Many need at least 10 to 20 minutes to fully take effect, while others need a few hours. The size of the crack or hole also matters; the larger the crack, the more time it will take to fill it properly.
Q: Is a stop leak a permanent fix?
While stop leaks may seem like a permanent solution to your problem, they only last a short amount of time. To truly fix a leak for good, you will need to take your car to a mechanic to get a better understanding of the leak.
Q: Do I need to drain the cooling system after using stop leak?
Generally, most radiator stop leak fluids do not require you to drain the system after applying the solution. However, read the labeling to see what the manufacturer recommends.
Q: What should I do if the sealant doesn’t work?
Remember, not all radiator stop leaks are permanent. If you don’t see an improvement after applying the fluid, you may need to take it to a mechanic for a more in-depth diagnosis.
Q: Are radiator stop leaks safe?
When used correctly in accordance with the manufacturer’s directions, stop leak is a safe product. However, it can cause more damage if misused. Because the product is designed to clog up leaks, it can clog your entire system if used incorrectly.
If you want a reliable and efficient radiator sealant, consider the K-Seal Multi Purpose One Step Permanent Coolant Leak Repair. You can save a bit of money and still get a great stop leak fluid with Bar’s Leaks Liquid Aluminum Stop Leak.