The 4 Best Radiator Stop Leak Reviews in 2018 – Buyer’s Guide

Last updated on August 16th, 2018 at 08:20 pm

Does the radiator stop leak work? Definitely! In the following review, we explore some radiator stop leaks for you. Radiator stop leaks had an uneventful start to their existence resonating with other chemical-based solutions.

Comparison Chart

bars leak 1150Bar’s Leaks 115016.910.00

There was just a significant amount of opposition to their emergence. Regardless, they are pretty efficient in their sole role of plugging leaks in the radiator, heating and cooling systems. It may also prove useful for leaks occurring on the head gasket.

Radiator stop leaks are pretty gentle on the system components such as gaskets and rubber hoses – you don’t have to worry about interference with their functioning. They are basically the most practical solution to not so significant problems in the radiator.

Before you can decide to go for a radiator stop leak, first assess the extent of the damage and determine whether more extensive work on the radiator is required.

Of course, radiator leaks are not miracle fix-it-all products. The best products are a little bit pricier, but their quality is mostly top-notch.


4 Best Radiator Stop Leak Reviews 2018

Genuine GM Fluid 3634621 Cooling System Seal Tablet – 10 Grams

Genuine GM Fluid 3634621 Cooling System Seal Tablet

These Genuine GM come in an easy-to-use tablet form and are designed to stop leaks the moment they start. They are more useful as a prevention measure as opposed to a remedy when the leak has gotten so bad.

In other words, you can occasionally throw in a pellet into the radiator even without having to wait for the leak.

The cooling system seal tablets also come in handy when you notice the “low coolant’ light is coming on more times than can be considered normal.

However, the case, having it around in your bonnet is the best thing for you as the car owner.

For ideal results, add a tablet every month, and they will stop those hairline leaks about to develop – they are a great prevention measure. This is the best coolant leak sealer for you.



AlumAseal ASBPI12-12PK

alumaseal radiator stop leak reviews

While this may not plug significant leaks, Alumaseal proves useful on the small ones.

It works best with aluminum radiators and holds everything together until you can purchase another radiator.

And if its hairline fractures that were developing, using this radiator stop leak may be the permanent solution for you – at least for a couple of months, of course.

This product works well with antifreeze and coolants. It treats systems up to 21L and is safe, quick and easy to use.

However, the product will not work with plastic radiators but giving credit where it’s due; this is the best radiator stop leak on the market.



K-Seal ST5516 HD Multi-Purpose One Step Permanent Coolant Leak Repair

K-Seal ST5516 HD Multi Purpose One Step Permanent Coolant Leak Repair

This K-Seal product might just be the permanent solution you have been on the lookout for. It is kind of functional and will work well with a vast host of cases.

The coolant leak repair is made for the heavy-duty engines such as tractors, RVs and trucks and may not be the solution for the small vehicles.

The product doesn’t stop with radiator repairs but goes further to include cracked gaskets, engine blocks and freeze plugs among others. It also mixes pretty well with antifreeze and is easy to use – you just shake, pour and head on to something else.

While it may not save you from the eventual hassle of having to purchase another radiator, it can be the stop gap product that keeps it together until you can acquire another radiator.

And another associated benefit is that you can use it as a prevention measure. A small amount periodically may go a long way into stopping a developing leak and saving you some real bucks, in the long run.


Bar’s Leaks 1150 Grey Cooling System Repair – 16.9 oz

bars radiator stop leak reviewBars is a typical go-to product for mechanics and car owners when faced with a cooling system leak. Among the factors responsible for its popularity include safe use.

Earlier versions of the chemical solution for radiator leaks mostly ended with more problems such as the plugging of the heater core.

This best radiator sealant leak solution comes in a highly-regarded original formula in a pelletized form that most users swear by its efficiency – it is a trusted product by auto-repair workshops and individual car owners. It is useful in stopping slow leaks and may act as a temporary solution for the larger ones.

Bar’s is compatible with a variety of anti-freeze brands and is one of the easy to use labels out there. With this radiator stop leak, you may be afforded ample time to come up with a better solution which is radiator replacement. This is one of the best plastic radiator stop leak.


How to Use the Best Radiator Stop Leak

It is important to note that radiator stop leaks do not present a permanent solution. As a matter of fact, the leaks they stop eventually find their way back. At the end of the day, you may be required to find the leak and manually plug it for a permanent solution.

However, they are an excellent stop-gap solution that keeps it together until you can make savings for a permanent solution. And if it’s a hairline fracture on your hands, radiator stop leaks can extend the life of the radiator by several months. Some people doubt their efficiency, but any auto-repair shop may let you in on the secret and tell you that they are not too shabby as a leak solution.

Ideally, follow the manufacturer’s advice to the letter and keep a close eye on the coolant. You can sometimes go overboard and apply two times the recommended amount. However, if that does very little to stop the leak, then you are better off sourcing for another radiator – it is not worth the hassle anymore.

To ensure efficiency, you should act within the shortest time possible when you notice a leak. Holding for later can even lead to much more significant problems that any solution with the radiator stop leak would not be sufficient.

Too much of the chemical solution is not the best as it can lead to problems with the heater core and other engine parts. Clogging is a possibility, but you can prevent it by following instructions such as changing the anti-freeze and flushing the cooling system.

If you happen to use the product and have the cooling system repaired, it is always advisable to power flush. Just draining the fluid is not sufficient. You need to change the antifreeze and flush the cooling system to get rid of excess radiator stop leak.

Always, the best thing to do is to have a stop leak in the glove compartment so that you can act quickly when you notice a leak. Just the same way you monitor other fluids such as oil and water, you should do it with the coolant. There is a tendency to overlook it entirely, and that is sometimes a recipe for disaster.

The best thing is to have a stop leak within your vehicle for such eventualities. It can be the difference between getting a new radiator right now and months later.


How to Fix Radiator Stop Leak

A car’s cooling system keeps the engine from overheating, avoiding a host of problems in the process. You see, your engine’s efficiency depends on the effective circulation of the coolant.

The engine bears the bulk of the work in moving the vehicle from one place to the other. In the process, it produces a significant amount of heat, which if left unchecked can spoil the engine and ground the vehicle – something you never want to happen.

The primary role of the coolant system is to circulate a blend of water and coolant through the engine and radiator, thereby bringing the temperatures down, and keeping your engine happy.


Coolant Leaks and Possible Problems

As the car runs, and you enjoy the ride, the temperature of the coolant hits the roof, expanding in the process. To prevent problems, the already expanded and excess coolant moves to a reservoir tank. However, the wear and tear can get to the system, and if not fixed promptly, it can lead to a host of engine problems, and expensive repairs.


Main Causes of Radiator Leaks

A weak radiator cap can as well be the main avenue for an overheated coolant. The coolant employs pressure to circulate the coolant effectively, and an ill-fitting cap can release this pressure leading to coolant loss. However, you can easily conduct a pressure test in the radiator to identify any problem.

An internal leak will not form a puddle of coolant under the vehicle. Instead, you will find yourself having to refill the radiator now and then to keep possible overheating at bay. An internal leak can come from a faulty head gasket or a block.

An external leak is the easiest to identify. For starters, you will notice that your engine overheats pretty quickly. You can also look for a hole or broken hose along the system. Other avenues that the coolant can use to escape, and which are easy to identify, include engine freeze plugs, heater core, and water pump.


Identifying a Coolant Leak

Before you can begin the inspection, make sure that engine cools sufficiently. You see, a hot radiator contains pressurized steam, which can forcefully spew out when opened, posing a safety risk.

Wear safety goggles if it is necessary to go under the car. Typically, the goggles will protect your eyes from possible falling debris.

There are various causes of radiator leaks, and each varies regarding severity. The easiest way that you identify a leak is through the collection of coolant under the car. If you are observant enough, you’ll notice that the reservoir tank is not at the level it should be. That can highlight a gradual leak somewhere in the coolant system.

Another sign of a leak is a sudden engine overheating. You can also smell out the leak while getting into the car. Typically, it is not so hard to identify a leak; it only takes your determination to find it.

To locate the leak, use a hose to clean the radiator of any coolant, debris, and grime. A clean radiator is easier to identify possible leaks. You can use paper towels to rub any excess coolant.

Start the engine and visually look for coolant running down the lines or radiator and listen for any possible hissing sounds as the pressure tries to escape. You can also use a pressure tester purchased from an auto store.

Install the tester in place of the replaced radiator cap and pump about ten pounds of pressure. If it shows a loss of pressure, then you have yourself a leak somewhere along the system. Look for these leaks by listening for hissing sounds and seeping coolant.


Fixing the Radiator Leaks

As the adage goes, there are various ways of skinning the cat. In the context of radiator leaks, there are various methods of sealing the leak and ensuring that your engine is running as it should.

  • Using a Leak Sealant: one thing that would make you happy is that there are various leak sealants you can purchase to seal that leak. And regardless of the brand you choose, the instructions for use are fairly the same across them. 

Switch the engine off, and allow it to cool before removing the cap. Pour the contents of the sealant into the coolant system, and top it off with a mixture of water and coolant if necessary – the top off is when the engine is low. Cap the radiator and start the engine. Typically, the leaks will seal off as the coolant seal makes its way around the system. Let it run for about ten minutes and allow sitting for the whole night as the sealant settles.

However, you should note that the use of leak sealants is what we can refer to as a stop-gap solution. It is temporary and for small leaks until you find a more permanent solution.

  • Using an Epoxy: you can purchase an epoxy to seal the visible holes and cracks from the majority of auto stores – it should not be hard. The first thing you should do is identify all possible holes or cracks, and clean them thoroughly. To prevent grease from affecting its effectiveness, use a rag dipped in brake cleaner to remove every trace of oil, and give it time to dry. Don’t attempt any sealing while the area is moist, lest it is impermanent.

Put some epoxy in your hands and knead it sufficiently before application on the affected areas. Spread it generously around on the crack and remember to keep it at least an inch thick. It is important so that it can easily deal with any coolant pressure and recurring problems.


  • Using Pepper: pepper is yet another method you can employ to hold it together until you can get home or the auto-repair shop. Let the engine cool and pour half a shaker of black pepper into the radiator system. The pepper will then collect in small holes as the engine and pressure try to blow it out, thus creating a temporary seal. And unlike the egg yolks, pepper can hold longer cracks, but temporarily.


  • Using an Egg: eggs are another stop-gap solution until you are ready for a permanent solution. To go about it, separate the egg whites from the yolks and discard them. You should remain with yolks from about four yolks.

Put them into the coolant system and start the engine, the same way you would a leak sealant. The eggs should hold the pressure long enough until you get to the auto repair shop.

Please note that the egg yolks method is less reliable than the commercial sealants and can potentially cause clogging troubles along the lines. Use it in emergency cases.


  • Checking the Repair: no matter the method of repair you use, make sure to check if it is still leaking after driving a short distance. And if it is still leaking, repeat the repair process.

If the cracks or holes are too big, they may be beyond repair, and a radiator replacement may suffice. Another thing to note is that pepper and egg yolks are not permanent solutions. They are to hold the leaks until you get home and use a commercial sealant or epoxy.

And if the level is down, refill the radiator with a 50/50 fusion of water and coolant.



There was a time that coolant stop leaks were used in new vehicles. There are whispers among those in the know that they are still in use with new cars, today.

The thing is they provide an extra layer of protection against nuisance leaks and prolong the life of your radiator.

The naysayers will say all sort of negative things regarding stop leaks. But the truth of the matter is that there are millions of vehicles on the road with this chemical solution within them.

The key is to apply just the right amount without overdoing it – if the radiator is burst, putting a lot of the stuff will not help the matters in any way.

The best stop leak for radiator can efficiently act as a stop-gap extending the life of your radiator even if for a few months. The extra time added by the stop leaks is worth the investment as it saves you from unexpected repair bills.

Hello! I’m Mike Maclennan and I live in Phoenix, Arizona. I work in the construction and home remodeling industry. Having used many tools over the years, I’ve decided to start this website and share my personal tools review. Thanks for reading my articles and I hope you’ll find the best tool for your needs.