The 10 Best Radiator Stop Leaks to Buy 2020

Radiator stop leaks had an uneventful start to their existence resonating with other chemical-based solutions. 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.

Best Radiator Stop Leaks – Reviews

Bars Leaks 1150
bars leak 1150

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.

In the following review, we explore some of the best radiator stop leaks you will find on the market.

1. Genuine GM Fluid 3634621 Seal Tablet

Genuine GM Tablet

These 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.


Alumaseal ASBPI12 – Simple but Efficient


While this may not plug significant leaks, it 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 among the best radiator stop leaks you will find on the market.


K-Seal ST5501 – Best Value for Money

The 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 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 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 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.


How to Use the Best Radiator Stop Leaks

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.


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 radiator stop leak 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.