Best Radiator Stop Leak On The Market: Reviews and Buying Guide

Best Radiator Stop Leak reviews

Did you know that excessive heat is one of the most common causes of vehicle engine breakdown?

When heat from friction and burning of fuel is too high, the pistons might snap, resulting in tremendous damage. That is what makes the radiator so important.

The radiator is a part of the engine’s cooling system that kicks in when the other cooling system parts are unable to cool down the engine sufficiently. It’s normally located at the front and houses a liquid coolant that gets released when the temperatures reach a certain level.

The coolant in the radiator veins picks up heat from the engine, and a fan helps beat air into the coolant, so it cools down.

Now, one of major the reasons why engines overheat and break down is an impaired radiator. There might be blockage preventing the coolant from getting released or, more commonly, a leak, which greatly reduces the levels of the coolant.

If you have spotted fluids under the front part of your parked car, then you may have a leak of the radiator fluids, and as that is a vital problem, it’s important to have a mechanic work on it.

But what if you’re in a situation that demands a quicker fix?

Say you’re in a hurry to get somewhere or there’s no mechanic nearby. Or, perhaps you don’t have enough cash to pay a mechanic.

In that case, a radiator stop leak product is your best option. It offers a simple and quick repair, preventing the radiator from leaking any further. But, as there are many brands, most of them selling ineffective products, purchasing a reliable radiator stop leak might be a little tricky; that’s why we’re here.

Today, we will walk you through the best radiator stop leaks on the market and provide you with tips on using them alongside other important info.

Without further ado, let’s get started.

TOP 5 Selection For A Quick Decision

Image Product Name Editor’s Rating More Info
K-Seal ST5501 Multi Purpose Permanent Coolant Leak Repair K-Seal ST5501 Multi Purpose Permanent Coolant Leak Repair

5 /5

5 out of 5 stars

Detailed Review And Price
ATP AT-205 Re-Seal Stops Leaks ATP AT-205 Re-Seal Stops Leaks

5 /5

5 out of 5 stars

Detailed Review And Price
Bar’s Leaks 1186 Liquid Aluminum Stop Leak Bar’s Leaks 1186 Liquid Aluminum Stop Leak

4.5 /5

4.5 out of 5 stars

Detailed Review And Price
Dike Temporary Stop Leak Dike Temporary Stop Leak

4.5 /5

4.5 out of 5 stars

Detailed Review And Price
Genuine GM (12378255) Fluid Cooling System Seal Tablet Genuine GM (12378255) Fluid Cooling System Seal Tablet

4 /5

4 out of 5 stars

Detailed Review And Price

Top 10 Best Radiator Stop Leak Reviews For 2020

1. K-Seal ST5501 Multi Purpose One Step Permanent Coolant Leak Repair

Kicking off our list, we have the K-Seal ST5501, which presents lots of benefits, starting with the fact that it is super easy to use.

The K-Seal ST5501 comes in the form of a solution in a bottle, and to use it, you just shake the bottle and pour the solution into the cooling system before running the engine as usual.

The product then circulates throughout the system, blocking the holes and cracks it stumbles upon. Amazingly, it is able to seal holes as big as 0.6 mm but doesn’t block the passages in the radiator or the heater core. It also doesn’t adversely affect the functioning of the radiator or the engine.

After the product has sealed the leaks with its fibers, the gases in the combustion chamber and the air from the atmosphere cause the product to cure quickly, so you start seeing the results speedily.

The results – a potent, long-lasting seal that can put up with the combustion chamber’s high pressure.

Looking for a product that you can use in several applications? The K-Seal ST5501 is one of the most flexible stop leaks out there as you can use it for sealing the following leaks in addition to the radiator leaks:

  • Engine leaks
  • Water pump leaks
  • Head gasket leaks

Highlighted Features:

  • Easy to use
  • Can seal 0.6 mm diameter holes
  • Doesn’t clog the heater core
  • Safe to use
  • Applicable to multiple types of leaks

2. ATP AT-205 Re-Seal Stops Leaks

If you’re looking for an effective, high-quality plastic radiator stop leak that is also excellent for your rubber seals or gaskets, the AT-205 Re-Seal would be a perfect choice.

What we liked about this product is that it effectively restores a seal that is worn or dried out without harming the internal components of the engine or the radiator.

Again, it doesn’t just stop leaks in the radiator; the stop leak works excellently for engines, transmissions, hydraulic systems as well as the power steering, stopping any leaks on seals or gaskets.

And the application is quite simple. You just pour the fluid in there as you would pour a coolant into a radiator and wait for it to work its magic.

Worried about the solution’s compatibility with the fluid in your car? You will be glad to know that the AT-205 Re-Seal doesn’t affect the functioning of your vehicle’s fluids like hydraulic oil, engine coolants or power steering fluids.

Plasticizer – do you know what that is? It’s the chemical that manufacturers use to make those rubber seals flexible and reduce brittleness. But, with use and as the seals get older, they lose plasticity and start wearing.

The AT-205 Re-Seal is composed of the same chemical, the plasticizer, and thus it’s able to effectively rejuvenate the flexibility of your rubber seals and gaskets and restore their sealing power.

Highlighted Features:

  • Solution in an 8-oz bottle
  • Compatible with vehicle fluids like hydraulic oil
  • Fast acting
  • Works for many components including engines, transmissions, and radiators
  • Doesn’t contain petroleum distillates, and therefore won’t break down or over-swell seals

3. Bar’s Leaks 1186 Liquid Aluminum Stop Leak

As you will discover later on in the buying guide, one of the best stop leak components is aluminum; it’s very effective.

The Bar’s Leaks 1186 is made of liquid aluminum, and if you want a product that is able to effectively seal leaks in the gasket and the radiator without clogging the heater core, then this sealant would be a great pick.

And guess what? You know the way the antifreeze lowers the temperature of the water so it doesn’t boil during summer or when the engine is hot? The Bar’s Leaks 1186 enhances this effect. It helps lower the water temperature, and that means it’s a better solution to your engine’s overheating issues.

But, you might be concerned as to whether you can add the Bar’s Leaks 1186 directly into the coolant. Yes, you can. The product was said to be safe for adding directly into existing coolant, and when we tried that, there were no negative issues, and the product worked just fine.

So, there’s no need to flush out the coolant before using the product.

Again, the Bar’s Leaks 1186 works with virtually all sorts of coolant colors from yellow and pink to green and blue. Whether your coolant is silicate based or non-silicate based, this stop leak is likely to be suitable.

The only issue we noted with this product is that it can’t be returned.

Highlighted Features:

  • Super-fast results – instant to 20 minutes
  • Works with all coolant varieties
  • Doesn’t clog the heater core
  • Helps lower the water temperature

4. Dike Temporary Radiator Stop Leak

Stop leak products are normally used as solutions to coolant system leaks. Now, what makes the Dike Temporary special is that it is used not only as a solution but also as a preventive measure to these leaks.

Rather than waiting till the leaks show up, why not get a can of the Dike Temporary and apply it? That could save you lots of cash in repairs.

One of the most notable advantages of this product is that it functions really fast. You just add a can into the radiator and run or keep the engine idle for around 15 to 20 minutes and you’re good to go. The duration is enough for the product to seal all those tiny cracks and holes.

If your gaskets are not sealing very well, the Dike Temporary will undoubtedly take care of that.

You know how some stop leaks will not differentiate between holes and passages and how they will mistakenly block the engine/radiator passages restricting effectiveness?

With the Dike Temporary, you don’t have to worry about that, as the product is designed to avoid blocking ducts and passages and to go only for the holes and cracks.

Highlighted Features:

  • Compatible with all types of antifreeze
  • Fast acting
  • Doesn’t block passages
  • Usable as a preventive measure

5. Genuine GM (12378255) Fluid Cooling System Seal Tablet

Here’s one for those who prefer tablets to liquids. The Genuine GM 12378255 comes in the form of five 4-gram tablets that are meant for use in the radiator system as a solution or preventive measure to leaks. The five tablets are enough for sealing small to medium-size radiator leaks.

Using this product, you don’t need to fret about the effectiveness of your coolant fluids, as the product is compatible with all coolants including dex cool. If anything, it enhances their effectiveness.

The Genuine GM 12378255 is non-toxic. That means that while handling it, you don’t have worries regarding your health. The only thing you have to worry about, actually, is the coolant fluids; these are quite hazardous to your health and need careful handling.

The use is also quite simple. You just crush the tablets and mix them in a cup with a little bit of coolant before pouring the solution into the radiator.

If the coolant levels were very low, be sure to top off the radiator with the coolant after adding the stop leak.

If you’re in need of a stop leak product that seals the holes and cracks for the longest time possible, then consider using the Genuine GM 12378255. Its effects are quite long-lasting.

Highlighted Features:

  • Five 4-gram tablets
  • Can be used with all coolant fluids
  • The effectiveness lasts a long time
  • Non-toxic

6. Bar’s Leaks 1194 Grey Radiator Stop Leak

Radiator leaks driving you nuts? Chill out and allow us to tell you about a product that might just be the solution to your troubles. It’s called the Bar’s Leaks 1194 Grey.

There are many radiator stop seals on the market, and some of them are good, but when talking about the Bar’s Leaks 1194 Grey, we’re talking of a product that’s not just good; we’re talking about a great stop leak. How so?

We discovered that just a small amount of the Bar’s Leaks 1194 Grey works better than almost double the amount of other stop leaks. That is probably due to the fact that it is a concentrate and possibly due to the manufacturer using revolutionary methods of production, giving the product double power.

Guess what that means. That’s right; you’re able to save both time and money. Time as you won’t have to keep adding the solution or wasting time looking for more radiator sealant and money as you don’t need much of the product.

Some of you, after learning that the Bar’s Leaks 1194 Grey is a concentrate with double power, might be concerned about the safety of this stop leak. Well, you’re right to be concerned, but as far as we’re concerned, the product is pretty safe, not just to you as a user but also to your radiator and engine parts.

Highlighted Features:

  • Works with all types of coolant
  • Easy to use
  • Highly effective
  • An economy choice

7. Bar’s Leaks HDC Radiator Stop Leak Tablet

What makes the Bar’s Leaks HDC tablet special is the efficient manner in which it works. First, the product works for both the internal and external leaks. When you crush the tablet and apply it to an external leak, the particles accumulate on the outer part of the leak and bulge inwards.

Internally, the stop leak gets subjected to high heat levels and subsequently gains better ability to seal the small holes and cracks.

When the coolant seeps into the crankcase, it contaminates the oil, and the result is reduced effectiveness, increased friction, and elevated temperatures in the engine. The Bar’s Leaks HDC breaks into tiny particles that block those small seepage passages, preventing the coolant from seeping into the oil.

And the best part?

The product is pretty efficient, acting in 20 minutes or less. That means you won’t get stranded along a road somewhere. As the application is also quite simple and straightforward, requiring no special skills, the product gets you back on the road in no time.

Another very notable benefit is the affordability the product presents. If you really need a low-cost radiator sealant, then the Bar’s Leaks HDC is definitely worth some consideration.

The Bar’s Leaks HDC also offers you lots of versatility. In that regard, it works safely and efficiently on different radiator materials, including metal, plastic, and aluminum. It also works well with gaskets and heater cores without clogging the ducts.

And here’s an interesting feature – the product contains a component that stops the water pump from rusting while also lubricating the pump seals.

Highlighted Features:

  • 60-gram tablet
  • Affordable choice
  • Quick action
  • Easy to use
  • Effective
  • Lubricates the water pump seals and prevents them from rusting
  • No acids or toxins
  • Compatible with plastic and aluminum radiators

8. AlumAseal ASLC16 Radiator Stop Leak and Conditioner Liquid

The AlumAseal ASLC16 is yet another effective stop leak product that comes with properties for conditioning the water pump.

Like the other amazing stop leaks we have discussed, the AlumAseal ASLC16 works well with all sorts of coolants, and again, the product is compatible with different cooling system materials including plastic, rubber, and metal.

Using the AlumAseal ASLC16 is pretty easy. You just switch off the engine and set the heater control once the radiator is cold. Then, you pour the product into the radiator and give it a coolant refill. Isn’t the process simple and straightforward?

The product also acts very quickly. If you drive the car for about 10 minutes or let it sit there for the same duration, the AlumAseal ASLC16 sets in and seals the leaks.

As this stop leak product is made in the US, we bet you can count on the quality to be excellent and the product to work efficiently.

Highlighted Features:

  • Works with all kinds of coolants and antifreeze
  • Able to stop leaks quickly
  • Easy to apply
  • Compatible with all cooling system materials including rubber, plastic, and metal
  • Conditions the water pump

9. ACDelco 10-5046 Dex-Cool Leak Detection Tracer Dye


We have told you about several stop leak products, and we thought, why not talk about a leak detection product?

The ACDelco 10-5046 is a fluorescent dye that traces leaks in cooling systems that utilize the orange-colored dex cool coolant. For great results, use this product along with the ACDelco UV Leak Detection Lamp Kit; the leaks will effectively be detected.

So, rather than having to clean the radiator and manually look for leaks or listen to hissing sounds trying to figure out where they’re coming from, why not use the ACDelco 10-5046?

It’s a lot more accurate, and it most definitely makes the process of looking for leaks easier.

Here’s one reason we think you should trust this product – ACDelco is a General Motors parts brand, and therefore we can say it possesses the one hundred years of experience, quality, and creativity that GM holds.

Although the ACDelco 10-5046 has not been around for a century, the fact that the ACDelco brand is under GM means it has the ability and experience to provide you with a useful product. If you truly want a professionally-made leak detection tool, then don’t hesitate to get the ACDelco 10-5046.

Highlighted Features:

  • 1-oz tracer dye
  • Affordable
  • Professionally-made
  • Compatible with the ACDelco UV Leak Detection Lamp Kit
  • Makes leak detection faster and easier
  • Effective

10. Bar’s Leaks 1150 Grey Cooling System Repair

As you will discover in the “top brands” section, Bar’s Leaks is one of the best stop leak brands on the market, and that’s why there are several products from this brand in our review.

Whether there’s water only in your cooling system or water and antifreeze, you don’t have to flush anything out before pouring in the Bar’s Leaks 1150.

But, bear in mind that if the system is particularly dirty or clogged, flushing it before using any stop leak product would be a good idea.

Again, once you have successfully used the product to stop leaks, you don’t have to remove it from the cooling system. You should, in fact, leave it in there so it can stop any future leakages and prevent overheating.

This stop leak acts pretty fast, sealing the leaks instantly in most cases and where it doesn’t work instantly, 15 minutes are normally enough.

Perhaps your vehicle has a significant number of leak points, and a single application doesn’t seem to stop them effectively. In that case, try making a second application.

There’s an interesting side of the product that we thought you should know. Apart from sealing the leaks and indirectly lowering the heat in the engine, the Bar’s Leaks 1150 contains an additive designed for reducing the heat directly.

The additive lowers the coolant’s surface tension, thus boosting the wetting ability and subsequently improving heat transfer and reducing the heat.

Hence, if your car engine is very hot and you need a product that not only seals the leaks but also reduces the temperature quickly, then the Bar’s Leaks 1150 would be your ideal choice.

Highlighted Features:

  • Safe to you and the cooling system
  • Contains an additive for active heat reduction
  • Seals leaks quickly
  • Compatible with all antifreeze fluids
  • Stops future leaks or overheating

Best Radiator Stop Leak Buying Guide For Beginners

Before you buy a radiator stop leak product, there are a couple of considerations you need to make. Realize that not every product out there will effectively cool down your system.

For example, the product might not even be compatible with the coolant you’re using and by the by, is it safe for your engine?

Let’s delve into the factors to consider before buying a radiator stop leak.

1. Clogging

One of the most common clogging areas is the heater core. Ensure that the product you’re buying travels through the engine fixing the leaks and does not compromise smooth operation by blocking important engine parts like the heater core.

2. Chemical composition

Different stop leaks use varying chemicals ingredients, and these ingredients determine if the product will efficiently work for your engine’s cooling system. The best ingredients to look for include liquid aluminum and Xtreme cool, as they are effective and largely safe.

If you’re not an expert with chemicals, you could observe what previous users of certain products say. If most of the users are expressing disappointment and airing safety concerns, then there’s a huge chance the chemicals are not very good.

3. Effect on the antifreeze

Various stop leak solutions neutralize the antifreeze solutions in your engine, and that is obviously an undesirable effect. So, make certain that the product you’re using coexists properly with the antifreeze.

The bottom line is, you should make sure the product you’re purchasing is completely compatible with the cooling system of your engine. As you shop, pay attention to the product’s formula. Keep in mind that most of these products contain either plastic or aluminum, but aluminum is a lot better than plastic.

Advantages of Using Radiator Sealant

Picture this – you’re driving to work in the morning as usual, then suddenly, steams start emanating from your car’s bonnet. You stop along the highway and open the bonnet to find the engine very hot, and you guess that’s a cooling system issue.

When you check under the engine, you notice a puddle; the cooling system is leaking quickly, and you feel you cannot drive the car any further. You start feeling stranded and blue, knowing that if you start making other transport arrangements, you will be late to work, and your grumpy boss will be steaming with anger.

Only if you had some radiator sealant with you in the vehicle! You’d add some into the radiator, top off the radiator with some coolant and drive to work with no problems at all.

You see how handy a radiator sealant can be?

Let’s highlight the benefits, shall we? Radiator sealants:

  • Offer a super-fast solution to a leaking cooling system
  • Are effective for the small cracks and holes in the cooling system
  • Present a relatively inexpensive repair option for leaking cooling systems
  • Are readily available (especially on Amazon)
  • Are largely safe to both the user and the cooling system parts
  • Prevent you from getting stranded along a highway somewhere

Types of Radiator Stop Leaks

There are three different varieties of stop leak products. They are:

  • Powder
  • Liquid
  • Tablets

Despite the difference in type, all these products work by creating a sealant over those little cracks and dents, preventing the coolant from dripping out.

The three types of radiator sealants are also applied in the same way. The user normally adds them to the cooling system through the radiator or the radiator reservoirs. They then have to drive the vehicle for a short time or leave it idle for a specified duration, based on the directions from the manufacturer.

Although powder, tablet, and liquid radiator sealants work in the same way, we would encourage you to go for liquids and tablets for the sake of ease of use.

With tablets and liquids, measuring the portions will be a lot easier than when you’re using a powder variety. Again, powders can be scattered by the wind.

One more thing – there are numerous budget radiator sealants out there; don’t go for these. The price might be very small, but what about the quality? Remember, the target is to go for a product that effectively seals those leaks, and if the product can’t do that, then it’s not worth buying.

Best Radiator Stop Leak Brands on The Market

1. Bar’s Leaks

Bar’s Leaks is arguably the best coolant stop leak brands on the market right now with a track record of success; this is apparent from the huge amount of positive customer feedback on their sealants. This award-winning brand has been trusted in the provision of reliable sealing and repair solutions for over 60 years.

No matter the kind of vehicle you drive, Bar’s Leaks is highly likely to offer you a great solution to the cooling system leaks.

And it’s not just about the cooling system leaks. This brand’s products are designed for a wide range of leak types, including those on the transmission, the power steering, and the head gasket as well.

The brand is US-based, and this is additional assurance regarding the quality.

2. ATP Automotive

ATP Automotive is a Chicago-based car parts brand that was founded in the 50s, and it’s one of the biggest radiator sealant brands with facilities as big as 92000 square feet.

If you’re looking to buy a radiator stop leak from the most supportive manufacturer, we will encourage you to go for an ATP Automotive product. The brand is also known to deliver the product to the buyer very fast and in a professional manner, especially regarding packaging.

3. AC Delco

Do you love General Motors? Perhaps you’d like the idea of getting a radiator stop leak product from one of its brands, known as ACDelco. In our review, we did not introduce the ACDelco brand as a supplier of radiator sealants but rather as a supplier of a product that helps you seal those leaks.

Rather than going through the tiresome manual process of finding cooling system leaks, which is, by the way, not very effective after all, why not get the ACDelco 10-5046 and the ACDelco UV Leak Detection Lamp Kit? These will help you pinpoint the leaks accurately so you can then use the best-quality radiator sealant to deal with them.

Some Radiator Leaking Symptoms – That You Need to Know

As a car owner, wouldn’t it be impractical for you to think that you will never have to deal with a radiator leak? This common issue has several causes and a number of signs as well. One of the causes is when the tubes carrying the coolant to or from the engine get raptured.

Sometimes, the leak may not be very obvious as the leakage might not be much, and sometimes the leak is more noticeable.

Keep in mind that when a leaking radiator is not attended to, the engine is likely to overheat and break down. That is why it is important to check your car from time to time to discover any signs of leakage early enough. Here are some of those signs:

1. A pool beneath the front part of your car

If the coolant is leaking out, there’s likely to be a fluid pool under the engine when you park the vehicle. If there’s an oily fluid (most possibly green in color), that’s a strong indicator of a radiator leak.

Realize that engine coolants are normally hazardous to human/animal health, and thus the pool should be cleaned immediately and disposed of properly.

2. Reduced coolant levels

The coolant is usually housed in tank reservoirs normally located at the front end of the car, under the bonnet of course. And normally, the tank’s cap is colored.

The levels of the coolant in the tank typically decline with time, but if you added the coolant a few days ago, but upon checking the levels you realize that they’re low the minimum mark, there’s most probably a leak somewhere.

Having problems locating the reservoirs? Why not ask a friend to help you out?

3. Discolored or corroded radiator

When the coolant leaks out, the chemicals it contains may discolor the radiator, and as a result, there might be corrosion. This mostly happens to the lower parts of the radiator, so be sure to check the undersides as well as the surrounding engines parts for any discoloration or corrosion, and if there’s any, clean it off first.

4. Overheating engine

The radiator’s work is to prevent the engine from overheating, and the coolant gets the job done. Therefore, it is only sensible that a leaking radiator will not cool the engine as required, and the result will be an overheated engine.

5. Defective hoses

Engine vibrations normally wear the hoses connecting to the radiator eventually, and loosening of the clamps also occurs. These situations make it easy for coolant leaks to occur, and therefore you need to check the hoses regularly for any leaking fluids.

How Does a Radiator Sealant Work?

Do you remember how a radiator works? It uses a coolant (distilled water-antifreeze mix) that passes through tubes to cool down the engine.

When there’s a leak of the coolant, that means the gaskets or tubes are have cracks or holes or that they’re not adequately tight. Consequently, the coolant leaks out, and the radiator is unable to do its work.

If you drive the car with a defective radiator and the engine heats up, the results can be severe, with some parts breaking off and others literally melting down.

To counter the situation, stop leaks act as plugging or blocking parts added directly into the coolant. The product travels through the coolant and once it comes across a leaking area, where it covers the hole or crack.

The process is as simple as that. Now, we need you to understand one thing – stop leak products only offer a temporary solution, suitable mostly for emergencies. If you need a more lasting solution, you will need to ask for help from a professional mechanic who will fix these leaking parts.

In the next part, we will explore various quick solutions for a leaking radiator. Let’s dive in, shall we?

Tips To Fix A Leaking Car Radiator

If you have observed the signs we talked about above (overheating, a puddle beneath the engine, etc.), then it’s time to fix the leak. But, before fixing it, you need first to locate the leak. We will go step by step, so you vividly understand the process.

(A). Locating the Leaks

1. Let the heat go down

With the radiator not working properly, it is likely that the engine is quite hot. The problem here is that the heat pressurizes the cooling system, and hence, if you remove the radiator cap immediately, gaseous coolant might get expelled, and it is pretty hazardous to your health.

So, give the engine several hours to cool down before you embark on the task.


Opening the hood will allow air in and speed up the cooling process.

2. Wear some protective clothing

You don’t want any coolant steams getting into your eyes, and that’s why you should put on some safety glasses. You might be thinking – but the engine is cool! Well, the pressures that had built up in the engine led to steaming, and there might be some steams left in there. In any case, you don’t want to take chances. Again, the sunglasses will protect your eyes from any flying debris.

Another important safety gear is a pair of gloves.

3. Clean the radiator

Washing off the old coolant leaks and any other grime will make it much simpler for you to locate the leakage points.

With a hose, spray the radiator as well as the adjacent parts with water and be sure to remove any puddles that might be underneath the engine. As you clean the radiator, look for any cracks on the radiator or its tanks.

Tip: paper towels will come in handy for wiping off grime, but it’s not necessary to use soap.

4. Turn on the car and check for new leaks

Immediately after starting the car, open the bonnet and observe the radiator and its surroundings closely. Do you see any fluids or steams coming out of a crack? Other signs to look out for include:

  • Hissing sounds from a leak that you might not be able to spot
  • Drops of fluids coming down from a crack or hole above

Note: you may have to switch off the engine to gain a locate the leaks more accurately.

5. Locate the leaks with a pressure tester

There are lots of pressure teters available for purchase in auto parts stores across the country.

Before using it, be sure to turn off the engine and allow it to cool.

Next, remove the pressure cap or the radiator cap and install the pressure tester in place of the cap; make sure the system is securely sealed.

Now, pump 10 lbs of pressure into the cooling system. If the tester shows there’s a drop in pressure, then you know there’s a leak in the system, and by following the sound of the leaking air, you can locate the crack or hole.

Tip: when looking for leaks, pay attention to the coolant lines and the radiator; these parts are more vulnerable to cracking as they age.

Warning: don’t add more than 15 lbs of pressure into the coolant system as that might ruin it or build new leaks.

(B) Fixing Coolant Leaks

Here, we’re going to discuss several quick ways in which you can fix that leaky radiator. In summary, the methods are:

  • Using a radiator stop leak product
  • Using epoxy
  • Using eggs – yes, eggs!
  • Using pepper

Let’s delve into each of them, starting with –

1. Radiator stop leak products

There are numerous radiator stop leak products on the market, and they’re meant for making the sealing task quick and effortless. Though the brands are different, these products largely utilize the same principles to work, with the only variation being the effectiveness. That is why we recommend you use the ones listed on our review or any other that you’re confident with.

Generally, you take off the radiator cap and dispense the solution into the coolant system before topping the system off with the coolant if the levels are low.

After that, you restore the cap and switch on the engine. As the stop leak product makes its way through the cooling system, it forms seals on the cracks and holes it comes across.

Tip: after running the sealant, let the vehicle remain parked for at least 12 hours, so the sealant sets optimally.

2. Using epoxy

You can buy some epoxy online or from an auto parts shop.

Once you have identified the cracks and cleaned them, rub some epoxy on your hands and apply it over the cracks. Be sure to apply a thick layer, so it efficiently withstands pressure. Give the epoxy at least 12 hours to set in and form a sturdy seal before you start the engine.

3. Using eggs

If you can’t get your hands on some commercial sealant or epoxy, and you need an emergency solution, get four eggs from your kitchen. Separate the yellow parts (or rather the yolks) from the egg whites and put these yellow parts into the cooling system.

Note: Egg yolks work in the same way as commercial stop leak products, though they’re not as effective.

Start the engine and let the yolks make their way through the system, sealing the tiny leaks they encounter.

Warning: egg yolks can clog the ducts of your cooling system, and thus we recommend using them only in emergency situations.

4. Using pepper

Pepper is another temporary solution for a leaking radiator. with pepper, you can slow down or stop tiny leaks long enough to get to a garage or home where you can do a more reliable repair.

Before applying pepper, allow the engine a few hours to cool down totally. Then, pour some black pepper into the coolant system. Like the eggs, the pepper travels through the system, and catch on the cracks, sealing them temporarily, enabling you to make a short drive safely.

5. Checking if it is working

Those are the best quick methods of fixing a leaking radiator but no matter which one you used, it is essential that you examine if it worked.

So, once you have driven the vehicle for a short while, stop and look for any of the signs of a leaking radiator.

Remember them? A puddle under the engine, an overheated engine, and so on.

If there are still leaks, apply some more of the product you used to seal the leaks.

Bear in mind:

  • Pepper and eggs are only temporary solutions, meant for emergencies. So, after the short drive that you need to make, make sure that you use some radiator stop leak product or epoxy to take care of the problem in a more permanent way.
  • If the levels of the coolant are too low, then it’s essential that you give the radiator a refill. Ensure the refill consists of water and coolant in a 50/50 ratio, so there is effectiveness.
  • If the cracks/holes are too big or many, then the best you can do is replace that radiator.

How to Use?

One of the quickest means of fixing a leaking radiator, hose or gasket is by applying a radiator stop leak product. The product forms a coat over the cracks and holes and keeps the coolant from seeping out. If you don’t want to get stranded along a highway somewhere someday, then it’s important that you learn how to use a radiator sealant and keep some in your car.

Fortunately, using a radiator sealant is a piece of cake, and in this section, we will go through the process bit by bit.

1. Buy a stop leak product

You can buy the product from auto parts shops across the country but the best, most convenient source is the internet. Go over the review section above. We have tested the products on there and we’re positive you will find them helpful.

2. Pour the sealant into the radiator

If you check on the product’s container, you might find some recommended measurements/portions. In most cases, you’re directed to pour the entire bottle in there. To pour the product, you will, of course, need to remove the cap first.

3. Turn on the engine

After starting the car, give the engine some time, so it warms up. That way, the stop leak product will get circulated in the radiator, sealing the small cracks and hole it comes into contact with. Ten minutes are enough for the product to circulate and reach out to all the leaks.

4. Perform a coolant refill

If there was a leak, we’re expecting that the level of the coolant had dropped. Hence, add some coolant till you achieve the recommended levels. The fluid you add in there should contain water and coolant in a 50/50 ratio.

5. Let the sealant set in

Turn off the engine and let the car sit there overnight so the sealant sets in and seals those leaks thoroughly.

Keep in mind that these products are not meant to be permanent solutions. Of course, they are much better and more long-lasting than eggs and pepper, but eventually, they will wear off, and you will need to have a professional mechanic repair the radiator or replace it.

Frequently Asked Questions (FAQs)

Have a professional mechanic remove and clean the gas tank, so the product doesn’t clog the system.
Sometimes the product will stop the leaks instantly, and at other times it will take 20 to 30 minutes to see the results. In case you still see the leaks 30 minutes after applying the product, try applying another dose
ormally, a bottle of the stop leak product treats four gallons of capacity. Therefore, a bottle is enough for a moderate-size cooling system or rather a 6 to 10 cylinder engine. For smaller systems, say a 4-cylinder engine, half a bottle should be enough.
No. Let the product stay in there so it can take care of any future leaks.
That is an indication that your radiator needs service. Normally, it comes as a result of not changing fluids as frequently as you should or using hard water instead of distilled/soft water. Scale deposits are formed in the ducts, and the deposits may crystallize or jell. Use a flushing machine or flushing agent to get rid of the deposits.
Generally, yes. It doesn’t matter what type of coolant or coolant color you have; the product will work just fine.
You can, but if you’re looking for the perfect results, then it’s better to pour it into the radiator. In the event that you’re unable to access the radiator directly, then detach the top hose and pour the stop leak in there. Reconnect the hose and follow the rest of the instructions for using a stop leak product.
Antifreeze is a component of the engine coolant. It prevents the water cooling the engine from freezing during winter or boiling during summer. Normally, the coolant contains antifreeze and water in a 50/50 ratio.
No. Several other issues can cause your engine to overheat, including:
  • A problem with the fan – perhaps the switch is not working
  • Clogged cores
  • Old antifreeze or sediment deposits clogging the cooling system
Leaks in the cooling system are normally small holes and cracks, and these are the result of corrosion.

Final Words

It is safe to say that a radiator forms a very sensitive part of a vehicle. It’s part of the vital systems that regulate your engine’s temperature and if it fails, and the temperature rises to dangerous levels, the engine might suffer some substantial damage. As such, you ought to be serious about its maintenance.

As one of the issues affecting the radiator and the rest of the cooling system is leaks, then having the best radiator sealant in your car and a few extra bottles in your garage is essential. Our review above is a careful analysis of the top rated radiator stop leak products, and we’re positive you will find them helpful.

Don’t wait until you get stranded along a road somewhere to realize the importance of a radiator sealant. Get the best radiator stop leak conveniently today through our links.



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