Tips & Tricks

Radiator Stop Leak Here: Really Working Stuff, Buyer’s Guide & Comparison!

Radiators are a standard part of any vehicle cooling system or home heating system, and as you can see, they have opposing applications in different locations. A radiator in the vehicle is used to cool the engine by transferring the heat of the engine through the water. This water heats up and is used to heat up air blowing into the car cabin when needed. At home radiators operate in pretty much the same manner, they pass hot water or liquid through the pipes to heat up the air around them.

List of Top-Rated Radiator stop leak products

Product ImageProduct NameFormMore Information
1. Bars radiator stop leak1. Bars radiator stop leakTabletMore Information
2. Alumaseal radiator stop leak2. Alumaseal radiator stop leakPowderMore Information
3. Blue devil radiator stop leak3. Blue devil radiator stop leakLiquidMore Information
4. Prestone radiator stop leak4. Prestone radiator stop leakPelletsMore Information
5. Lucas radiator stop leak5. Lucas radiator stop leakLiquidMore Information
6. Irontite radiator stop leak6. Irontite radiator stop leakLiquidMore Information
7. Dike radiator stop leak7. Dike radiator stop leakLiquidMore Information
8. Johnsen’s Stop Leak8. Johnsen’s Stop LeakLiquidMore Information
9. Liqui moly radiator stop leak9. Liqui moly radiator stop leakGranulesMore Information
10. Liquid glass radiator stop leak10. Liquid glass radiator stop leakPasteMore Information

As such, radiators work through two methods that work together, they use convection to transfer the heat of liquid passing through their pipes to heat up the metal walls of the radiator that then use conduction to transfer that heat to the air.

A radiator is made up of five basic components; the pipes that hold the liquid, the fins that transfer the heat, the valves that regulate the flow, the liquid or water itself that is used to transfer the heat, and the heat source. In vehicles, the heat source is the engine, and in home heating, the heat source can be a boiler system, solar energy system or a plain old fire.

Leaks in radiators can occur in any of the metallic components that are used to transfer the liquid. A leak causes a drop in pressure, leads to corrosion of the surrounding area to the leak and reduces the overall effectivity of the system. In fact, in vacuum based systems, a leak can stop the process of heating by significant percentages.

If there is a leak in valves you cannot stop the leak with a quick fix, you need to replace the components. With a leak in the piping system, you can add patches and fix them mechanically, and with the fins you can use a quick fix solution such as a stop leak radiator liquid or powder that will plug up the hole as an intermediate solution, giving you time to arrange a full fix or replacement.

In this article, I present you with 10 of the best radiator stop leak products, and these 10 are based on radiator stop leak reviews, as well as actual tests to see which products are the best stop leak for radiator including radiator stop leak powder too.

Now let’s look at the list of the top 10 best radiator stop leaks today.

The Best Radiator Stop Leak Products:

1. Bars radiator stop leak

Bar’s Leaks Radiator Stop Leak Tablets are a compressed radiator stop leak powder compressed into tablet form much like a pill.


Bars Radiator Stop Leak Tablets are comprised of substances that inhibit the formation of rust and scale, neutralize pH imbalance, control electrolysis, lubricate and seal internal cracks, holes and other leak forms.

To use this product you insert a tablet into the coolant liquid, and once immersed in the liquid, the tablet starts to dissolve — the particles in the tablet and flow with the liquid to all points in the system. These particles are attracted to the leak area that usually pulls the liquid towards it due to vacuum pressure and seals up into the areas. This product is best used in cast iron and aluminum radiators, and it burns at 5000°F, so it’s extremely stable for any car or home radiator system.

This product is harmless to plastics and metal components and is compatible with all anti-freeze liquids.

2. Alumaseal radiator stop leak

AlumAseal Radiator Stop Leak Powder is a metal-based compound that seals radiators internally by depositing a compound that settles into the damaged areas.


All you do is pour a packet of AlumAseal into any cooling system, and it will work with all anti-freeze additives. This powder mixes with the liquids and moves to all the locations in the system, filling up any cracks, holes, and pores that provide a leak.

You apply this powder when the engine is off, pour it into the radiator, seal the radiator and then drive around to help mix the powder through the system.

This product is safe to use in all plastic and metal radiator systems.

3. Blue devil radiator stop leak

BlueDevil Head Gasket Sealer is used to repair and seal leaks in blown head gaskets, warped or cracked heads, heater cores, and freeze plugs.


BlueDevil head gasket sealant is a liquid and not a solid sealant solution. As such, it flows into any to metal, aluminum, cast, alloy, or plastic system sealing up the leak locations for longer lasting performance. This brand is best used to help fix Head Gaskets, Warped or Cracked Heads, Heater Cores, and Freeze Plugs.

Take note that this is not a permanent solution when used with warped or cracked components, and should be used as an emergency solution for you to drive to repair the damaged parts.

4. Prestone radiator stop leak

Prestone radiator stop leak is a solid-state powder in a tablet form that uses Kevlar particles as a sealant for leaking radiator systems.


The Prestone formula is a non-metallic leak formula that uses Kevlar particles to seal leaks up to 0.020″ X 0.5″ in size. The tablets come in small pellet form, and you add them to radiators, water pumps, and heater cores. They act as an internal surface coating, and coat all the internal surfaces including areas with cracks, holes, and pores, creating a solid and secure internal lining to your radiator.

5. Lucas radiator stop leak

Lucas K-Seal K5501 Coolant Leak Repair is an efficient stop leak formula that is used to seal up most radiator leaks.


K-Seal is a liquid formulation with particulates suspended in the solution. The particulates bind with the internal surface of the radiator system, as well as to gaskets and seals. All you need to do is pour in K-Seal K5501 Coolant Leak Repair to your coolant system and then run the engine as usual.

This is a great fix solution, and is perfect for minor leak problems, providing an effective coating to stop and also prevent leaks from occurring.

6. Irontite radiator stop leak

Irontite is a liquid radiator stop leak is all weather solution and works as a Pour-and-Go formula with all anti-freeze liquids solutions.


Irontite is a very fast acting radiator leak stopping solution that works with all standard radiator coolant systems and is a great product that will stop head and intake gasket, radiator, and other coolant system leaks.

The product is designed not to clog heater cores and comes with special microfibers that are attracted to the leak areas, plugging them up and sealing the system for very long periods of time.

What’s great about Irontite is that it works in all weather conditions, from freezing to hot weather and is relatively fast compared to many other products. It is used for sealing leaks in Radiator, Head Gasket, Cylinder Head and Engine Blocks in Gasoline or Diesel Engines.

7. Dike radiator stop leak

DIKE’S advanced formula is a liquid radiator stop leak solution for all vehicle types.


This product, when poured into any car, van, or truck water cooling system provides an emergency solution for repairing leaks on the go. When you are driving and a leak springs open, having Dikes formula in your care will enable you to treat the coolant system in a fast and timely manner. This is like a first aid kit for radiator leaks and will give you an immediate patch that allows you time to get to a garage to fix the problem.

Unlike other products, Dike does not pretend to be a permanent fix, it is an emergency solution for emergencies on the road and will give you a great immediate fix. After pouring Dike into the affected system, drive to your mechanic for a complete check and repair.

8. Johnsen’s Stop Leak

Johnsen’s radiator stop leak number 4918 is a liquid solution applied to radiators only.


This product, when added to the cars coolant system, will provide an immediate solution to stopping and plugging up leaks. It is not a permanent solution and is a non-clogging formula that will give you time to reach a garage or radiator mechanic for proper repair.

All you do is add the bottle to the affected radiator coolant and let drive off.

9. Liqui moly radiator stop leak

Liqui Moly is a car water coolant system stop leak solution that provides particulates for sealing up leak areas.


Liqui Moly radiator stop leak is an exceptional solution for all aluminum radiator systems. This product comes with conventional coolant water refiners and antifreeze compatibility and is capable of sealing up hairline cracks and small leaks. This brand does not damage your water pump or heating circuit and is best used as a preventative measure when in doubt.

You apply this formula when the engine is running, and pour the contents of the bottle into the cooling liquid at the engines operating temperature. Close the system and wait 10 minutes with the engine working before driving off.

10. Liquid glass radiator stop leak

Liquid glass is an externally applied sealant that is used to seal cracks and holes in radiators physically, Engine Blocks, Cylinder Heads, Freeze Plugs Head, Gaskets, and Heater Cores.


This is a metallic paste that when applied to the different surfaces, hardens and seals the affected area, as well as withstands up to 538oC.

This product works with all holes that have a diameter of up to 30 thousandths of an inch and repairs any length of cracks in engine cooling systems with a diameter of 15 thousandths of an inch. Once cured this brand withstands pressures of up to 3,000 pounds per square inch.

So, if you know where the leak is, and don’t want to pour anything into your system, this external solution is a perfect option for you.

Does radiator stop leak work?

Radiators are constantly working components in the engine system, and they also continue to work even when the engine is off, only because the liquid in the coolant system sits within the system. As such, there is always external and internal pressure on a car radiator system.

Leaks are more common than most drivers realize, where small unnoticed leaks affect the performance of the engine, many such leaks are so small that you rarely notice them until the breach widens. Therefore, to be sure, it’s always good to add some form of stop leak coating material to the radiator system just to maintain more secure surface integrity between the systems internals and the liquids flowing through them.

  • Usually, the cooling system leak starts at the following sources:
  • The water pump shaft seal
  • The seams of a radiator where the plastic tanks are joined to the core
  • The heater core
  • The intake manifold gasket
  • The cylinder head gaskets
  • In hairline cracks in the cylinder head and engine block
  • Casting porosity from the factory

Stop leak products will work in most systems, but they will not work in a rotating shaft seal where the constant torque and pressure affect the area.

Stop Leak products come in a variety of formulations, and they contain different materials to perform the same job. These materials are usually particulates suspended in a liquid, or in powder, granule and tablet form of the materials that dissolve into the radiator fluids. These materials include:

  • Ceramic Particles
  • Metallic particles (aluminum, copper, iron)
  • Ground up almond shells
  • Ceramic fibers
  • Sodium Silicate

How do stop leak products work?

Different materials work in a different way, and there are short-term solutions as well as more permanent solutions.

The materials define how the stop leak solution will act, and this is the way each one works within a radiator system.

Filler products including ceramic or metallic particles and ground up natural products such as pepper, cinnamon, and almond shells work under the pressure of the cooling systems flow, and circulate all around plugging up any leaks. They also tend to plug up other parts that are not leaking and as such, are not permanent solutions, or even good solutions. These solutions also get flushed when you replace the coolant liquid.

Ceramic fiber or micro-sphere nano-technology are extremely small versions of the standard filler products but are designed like fibers that form a mesh that covers the leak. Any leak area creates a negative pressure point in a sealed system. As such, the fibers are attracted to these low-pressure points and seal them up first. The extremely small fibers or spheres circulate just like other filler products and embed into the gap. As more fibers attached to the first fibers, they build a mesh which hardens and cures with engine heat. This types of sealer provide a more permanent seal, even if you flush the system later on.

Sodium Silicate or Liquid Glass is a more permanent solution but only works in the hotter parts of the engine where a leak might appear. As such, these products circulate through the system, and when they reach a leak in a hot area, such as a top cylinder metal ring on a head gasket or a coolant passage metal ring in a head gasket, the particles begin to melt forming a plug. Sodium silicate melts at 212-221°F. After it has molten, it only remelts at a much higher temperature of 1,490°F. As such it forms a semi-permanent seal. It also doesn’t clog up the system unless it melts into larger blocks of “glass.” In some instances, sodium silicate and metals are found in combination.

The viability of Stope leak Products

Stop leak products are not one cure for all ailments. Pinhole leaks are not permanently plugged by a stop leak product and will eventually grow due to external corrosion. Remember, a leak is not one-sided, it’s a crack or a hole from the internal to the external surfaces. As such, solving the leak internally does not solve it externally.
Also, a stop leak solution does not work on water pumps, do not work around revolving components and will not seal a crack in a coolant reservoir. As such, when you have a leak, don’t think that a stop leak is a permanent solution. It is not, and you need to get the components fixed or replaced.

How to stop radiator leak with black pepper

There are many home remedies for every consideration, including the use of black pepper. This is not a recommended fix, and while it is not meant to be a permanent solution, only a plug it to fix it later solution, it has a lot of issues that can cause more damage than good.

You might get a better smelling engine, maybe drop in a spoon of cinnamon and some garlic powder too, and convert your car into an olfactory of cooking smells. Some might suggest adding eggs, why not, maybe add a plate of chips and a good rump steak too.

Black pepper is a myth and while it will act it plug up some cracks, just as any powder that doesn’t dissolve completely in the coolant liquid, black pepper will clog up other internal components leading to far more damage than good.

How long does radiator stop leak last?

A typical question with multiple answers. It depends on the leak and the solution. There is no one answer, and anyone that tells you otherwise is a liar.

As mentioned above, there are different solutions ranging from biological, ceramic and metallic products — each one is delivering different style and level of performance for different sections of the radiator system.

Some leaks might be simple microcracks or pores that can be solved with a standard stop leak solution, and your radiator will continue to work without issues for up to 50,000 miles. However, if you think that it’s wise to drive around with a leak and a plaster, then don’t be surprised when your radiator rots away completely.

The only permanent solution is to identify the leak, provide a first aid fix, and then take it into a garage or mechanic and have the cooling system fully checked for more, as a rule, one leak usually means there are more problems in the system.

How to use bars radiator stop leak?

Bar’s radiator stop leak is very simple to use. You pour a bottle of the product into a cool radiator, preferably with the engine off and fill up the radiator tank until the tank reaches the correct level. Close the cap and idle the engine for 15 minutes, you can leave it on idle for up to 30 minutes too if you want to be absolutely certain. That’s all there is to adding Barr’s radiator stop leak solution.

How to stop a radiator leak at home?

Home radiator leaks are not like car leaks. These systems are not used to cool water but to heat water up and are much larger systems by nature and by the application than a small car or even truck radiator system.

As such, you will not be using a stop leak solution on a home system. You will need to perform a mechanical repair that can be as simple as sealing a leak using various metallic plugs with welding apparatus, to changing pipes, radiators, valves, and seals.

The first step is identifying the leak, remember that a house radiator system is a high-pressure system. This means that a leak will severely damage the operation of the system, and will very quickly change from a small leak into an exploding leak if not dealt with immediately.

So, before you begin, identify the source of the leak and close the system down completely. If the leak is coming from a pipe in the system, the easiest solution is to replace the pipe. If however the leak is formed the radiator then you need to replace the entire radiator since a leak is a sign of internal corrosion and that’s the end of the radiators life.

There is a quick fix that will let you use the radiator until you get a replacement, and that’s the application of a plastic resin sealant, which is only a temporary solution and should be used with care, which means try not to use the radiator in question, if possible, close it, bypassing it from the entire system. That’s one advantage that some home radiator systems come with. You can close off a radiator unit without affecting the rest of the system. In others, where the radiators are fixed into a single system, turning one off will close off the water flow to the rest. (Older systems)

Leaking from Radiator Valves and Spindles

A less costly leak is a leaking radiator valve, and even better (if there is better in a leak) is the spindle. In both cases, all you need to do is close the system and drain the radiator. Then you turn off the supply valve and the lock-shield valve and don’t forget to have a bucket handy, so you can catch all the water that accumulates in the valve.

Undo the union nut and release all the water, then once the valve is empty, use PFTE (Teflon) tape to wrap the valve tip. Reseal the union nut, open the valves, refill your radiator and then turn the system back on.
For a radiator spindle, which is better than a valve leak, all you need to do is turn off the system, then tighten the gland nut. If this doesn’t work, undo the gland nut and wrap PTFE tape on around the spindle and tighten it back in again.

Radiator Pipe leaks are either solved by tightening up the joints using a spanner, or disassembling the pipes and using PTFE reassembling them. Actual holes in the pipes demand you replace them.

Other solutions include replacing valves and body parts. To do so, you need to know which system you have, or adversely, you can take out the broken component and search online or got a radiator specialist to find a universal or brand match.

No matter what you need to replace, you must always close the system and rain all the water out of it before you begin dismantling components for replacement or repair.

Preventative and Protective Measures

One of the best solutions that helps prevent leaks in a home radiator system is the use of anti-rust/corrosion additives that are added to the water and prevent rust and corrosion from forming in the first place.


I am not a great proponent of stop leak solutions as a permanent solution, but I do believe that they can be used lightly and for temporary performance. It’s always best to let a professional check the entire system and then fix the leak properly. Having stated this, there are so many products and home remedies out there; it’s time to look at each one and consider what is best for a leaky radiator.

Cinnamon vs. Stop leak for radiator leaks

Cinnamon is powdered tree bark and is a temporary solution for fixing some leaks in a radiator system. However, as tree bark, it converts into graphite when exposed to extreme heat, which leads to gunking up the system. Now Cinnamon might give you a fantastic smelling car, but it will lead to some serious damage. As such, it’s best to take a standard ceramic or metallic Stop Leak solution that can be flushed from the system after use without causing too much damage.

Bottom line: don’t use cinnamon, unless you are baking cookies.

Pepper vs. Radiator stop leak

Just as I wouldn’t use Cinnamon, I won’t use black pepper, which is best used as a condiment and not a car maintenance material. If you have a small leak and no immediate solution. Drive to the nearest garage. If you live in the middle of the Kalahari Desert and there are no garages near you for thousands of miles, then book an Uber, or call for a tow. All condiments and pastry materials will gunk up your system and cause more damage than good.

Blue Devil radiator and block sealer vs. Stop Leak

The difference between products is based on application. Having stated this, there is one issue with certain products that I hate, and I mean hate. I hate it when companies such as Blue Devil state: ” Permanent repair for radiator and block leaks.” And then add “Works effectively on plastic, aluminum and/or metal radiators.” This is so much BS it’s more BS in content than in words used to make the statement. There is no on stop leak product that provides a permanent solution, and especially one that works on all metal and plastic options. The very fact that they state this makes me ignore them immediately. As such, if you have to compare a product, don’t include Blue Devil.

Blue devil vs. Bars

As mentioned in the above comparison, I don’t like Blue Devil, and when you compare the literature between Bars and Blue Devil, you get the immediate result. Bars is a professional company with a professional approach that does not come out with bombastic lies of one cure for all and permanent. Bars also explains how to use the product and its limitations. As such, Bars wins hands down.

Bars leak copper vs. aluminum

This is a good question, and the answer is based on application, especially when considering the differences between two products from the same manufacturer.

Essentially, liquid aluminum is not a better product than the copper, and copper is not better than aluminum. In fact, metal stop leaks don’t really work well at all, but they sound nice.

The issue with metal leak compounds is that the metal flows through the entire system and that includes the heater cover, the radiator tubes, and the pump. As such, they tend to clog up systems due to the “weight” of the particulates, and this causes systems to overheat. Sure, you might have temporarily solved the leak, but now you have to replace the entire cooling system since you clogged it up with aluminum or copper powder.

The bottom line is this; it doesn’t matter if you have aluminum, copper, titanium of vibranium (Marvel metal universe metal). These particulates will not seal a leak for long, will clog up the system and eventually cause more damage than good.

So, bottom line; both copper and aluminum are as good and as bad as each other, the only difference is in color. Oh, and copper corrodes much faster than aluminum, so expect green coolant liquid even if you didn’t add anti-freeze.

Blue Devil vs. K&W

This is another Blue Devil comparisons, and sorry folks, you know my opinion of Blue Devil products. Once stated as a permanent solution, makes it hard for me to take anything from them seriously. It’s like taking Rhino Horn powder for erections, costs a lot, and doesn’t work. The bottom line is this, K&W is a much better company with better products, and it’s a hands-down win for them.


I was told that my aversion to Blue Devil seems weird in the face of the fact that I included it into the top 10 list above. Well here is my answer: Blue Devil works as a quick fix solution and is very similar to most other products on the market. The reason I don’t promote using their products is that of their false claims that lead people to believe they are getting a permanent solution for a leak. There is no permanent solution, and the only permanent solution is to replace the system. As such, they are as good a temporary solution as most others, but when it comes to a straightforward integrity issue, I would rather go with a company that promotes a product with integrity and truth and not some snake oil sellers one cure for all solution.

More In the Garage Reviews – See our best: