Radiator Stop Leak Review

Updated on January 22, 2019
Benjimester profile image

You don't want to neglect a cooling system leak. The first time I had one, the majority of my coolant disappeared in a day.

What Is Radiator Stop Leak?

I recently wrote an article about engine oil stop leak and its benefits, and I wanted to follow up with an article on radiator stop leak. Even though the two products have similar names, they are not the same at all.

Stop leak: Stop leak varies greatly depending on what system you're using it for. Inside the engine, stop leak is designed to treat the rubber seals that keep oil from entering into the fuel mixture for combustion. Stop leak for engine oil is designed to soften and expand the rubber and keep the rubber seals fresh and working.

Radiator stop leak: Radiator stop leak is different. This product is designed to seal a leak that's happening somewhere in the cooling system, and if not used properly, side effects might ensue.

Radiator stop leak is a goopy substance that can cause quite a lot of trouble down the road if you're not careful. So before you go out and buy radiator stop leak, open up the hood of your car and see if you can't specifically locate where your leak is coming from. Many times, the leak will occur on a part of the cooling system that's easy to repair without the use of goopy additives like radiator stop leak. Below, I'll diagram what the cooling system looks like and how to try to diagnose where your leak is coming from.

When to Use Radiator Stop Leak

In the following section, we'll go through how to diagnose and find where your leak is. But sometimes, especially in certain older vehicles, there isn't just one leak. Sometimes the whole system needs to be treated. There are certain old Fords and other manufacturers that had numerous problems with the cooling system as a whole. In this scenario, radiator stop leak might be an excellent way to go, because it will treat the whole cooling system all at once. Just make sure you get the very best radiator stop leak out there. If you get a poor stop leak, it can clog up your pipes with goopy stop leak and cause unwanted pressure variances and larger problems. I've left you a link at the bottom to a product that has a lot of positive testimonials. Hopefully that will cut down on any side effects that sometimes pop up from poor quality radiator stop leak.

If, however, your vehicle isn't an old beater and you think that your coolant leak might be fairly well localized to one spot, go through the next section and see if you can't identify the specific area where your radiator leak is. You don't want to neglect a cooling system leak. The first time I had one, the majority of my coolant disappeared in a day and I burned through a few quarts of oil because my engine got so hot. I had to replace not only my radiator but get an immediate oil change, as well.

This is a picture of an aluminum heat sink.  It's not a radiator, but is similar.  Depending on the severity of your leak, radiator stop leak will fix most mild leaks inside your radiator.
This is a picture of an aluminum heat sink. It's not a radiator, but is similar. Depending on the severity of your leak, radiator stop leak will fix most mild leaks inside your radiator.

Finding Your Leak

There are three main components to the cooling system of your car. The first is the radiator itself.

1. Radiator: This component is basically just a large aluminum heat sink, like the ones you might see on top of the processor inside your computer. The water flows from the hot engine through the radiator, with air rushing over the surface from the fan and from the outside air, getting cooled. Then the water flows back into the engine to reabsorb heat. The two tubes that carry the water back and forth from the engine are called the upper radiator hose and the lower radiator hose. Those are the second components of your cooling system.

2. Upper and Lower Radiator Hoses: The upper radiator hose carries the hot water from the engine into the top of the radiator to be filtered through the radiator and cooled. The processed water then flows through the lower radiator hose back into the engine to reabsorb heat. These two tubes, because they're made of rubber and undergo constant changes in heat, can wear out easily, or else become loose and begin to leak. The first thing you ought to check is whether or not your upper and lower radiator hoses are attached firmly and whether or not they're leaking. If you warm up your engine and open up the hood, leaving your car running, you should be able to tell whether the leak is coming from one of these two hoses, or whether it's coming from the radiator itself. If the leak is coming from one of the two hoses, you're in luck because they're pretty easy to change.

The is the icon for windshield wiper fluid. Don't pour radiator stop leak in here or you might have a big problem.
The is the icon for windshield wiper fluid. Don't pour radiator stop leak in here or you might have a big problem.

3. Coolant Overflow Tank: The third component of your cooling system is the coolant overflow tank. This is generally a clear plastic tank that's off to one side of the radiator. Most cars have two plastic tanks that each hold about a half a gallon of liquid. One is the coolant overflow tank and the other is the windshield wiper fluid tank. You'll have to identify which one is which. The windshield wiper fluid tank generally has the icon pictured to the right stamped somewhere on it or on the cap. If you really do have a leak in your coolant system, then odds are that your coolant overflow tank is completely empty. When the car is cold, the coolant overflow tank is at it's fullest. As you drive and more coolant is flowing through the system to keep the engine at a safe temperature, the coolant overflow tank adds more liquid to the cooling system. There's a chance that your leak is coming from the coolant overflow tank, but this is pretty rare. If the tank gets cracked and begins to leak, you'll be able to see droplets of coolant falling from it. If that's the case, then you're in luck again, because the coolant overflow tank is pretty easy to change out.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.


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    • profile image


      4 months ago

      What can i do if i put Bars stop leak for the radiator(the cooling system) in my engine(where you put the oil. I had gotten. Oil sop leak and i thought i had gotten oil sop leak again but i got radiator stop leak by accident and put it in my engine. What can i do to fix it. Is there any hope for my 91 Toyota Privia

    • profile image

      Tesfamariam gebrelibanos 

      5 months ago

      I have astra truck. Water leaks through a radiator i have used more stop leaks to avoid this leakage. After a time vehicle radioter leakage avoided by repairing the radiator. But overheating is occured after a time and belt, fan, water pump, water level all checked they are ok. But the problem is not identified still now. Please dear help me for the solution.

    • profile image


      12 months ago

      I have a small leak in the right (drivers side) bottom of my radiator, a 1995 , 308, Olds, 88, Royal. Not sure if I should put stop leak in it or pull it out and have it boiled out and repaired. Doubt that I will keep the car much longer. I have worn the interior out. Runs and rides better than my Lincoln. What do you suggest?

    • profile image


      2 years ago

      What about LION STOPLEAK?? ANY one out there who experienced using LION STOPLEAK??

    • profile image


      5 years ago

      What about Wynns Radiator Stop Leak?

    • cardoctor2 profile image

      George Christ 

      5 years ago from http://www.auto tune up and repair options.com

      Leaks in the cooling system is nearly always an engine killer if not caught in time. After the leak, stop leaks are sought out.

      New stop leaks for radiators being of clear liquid, that stay liquid, like in the Mega Power Brand, flow like water until a leak exposes them to air - where coagulation seals - like blood in a cut. These offer ongoing stop leak and stop leak without offering disadvantages of fibrous, stringy, or find particles of metal in them.

      Mega Power RS3 clear liquid radiator stop leak treatment, also neutralize acids that cause the leak - a very good second advantage. Mega Power also includes ability to pack more coolant into a square inch - by removing free oxygen, a rust producer, allowing more heat transfer from motor to coolant to outside air, while doing so. An advantage to ATF fluid circulating to the radiator, trying dump its high heat load out of its fluid into the treated coolant, helping cooled down ATF to cool and lower hot gear and bearing temperatures in the transmission - a longer life aid.

      Mega Power's three beneficial values to stop the leak and neutralizes acids, and add years more anti-leak protection, and addition of greater heat transfer values - are valued by many car and equipment owners.

      For those who frown on older type stop leaks and their disadvantages of fibrous, stringy, or find particles of metal stop leak products - which can choke off the tubes in the radiator - may want to learn more about Mega Power at this link. http://www.auto-tune-up-and-repair-options.com/Sto...

    • profile image


      6 years ago

      For a radiator leak on my old Ford Ka I flushed it with some K-seal http://www.k-seal.co.uk/k-seal . It was recommended by my local garage and it did the trick. 4 months in and no leaks and no problems.

    • profile image


      7 years ago

      I agree with Fred. Ive used Rislone on a few different vehicles and it worked very well every time. All the leaks that ive had were intake leaks so i can tell you that the product worked very well for intake leaks. I had an intake leak over 3 years ago and still to this day, it has fixed the problem. Only once did i notice an issue and that's when i used rislone for an intake leak, i only ran the vehicle for about 15 mins, checked the leak and it was fine. I never ran the vehicle for about 2 weeks and the first time i did drive it, i noticed it was over heating. I shut the truck off for 5 mins then ran it again with no over heating. This happened 2 more times when i let the truck sit for a length of time. My suggestion is to not let the truck sit for to long, once a week take it for a 10 minute drive and there will be no clogging issues.

    • Benjimester profile imageAUTHOR

      Benji Mester 

      7 years ago from San Diego, California

      Yeah, upper radiator can be a bit tricky because of the placement of the crack. I'd probably not use a stop leak for that one.

    • profile image


      7 years ago from Grants Pass,Oregon,United States of America

      Now if one of you guys will tell me how to repair a small crack in upper radiator tank on my 91 Camry i will be quite happy,i have heard they cant be repaired [PLASTIC]

    • Benjimester profile imageAUTHOR

      Benji Mester 

      8 years ago from San Diego, California

      Thanks Fred for that cool explanation. It's clear that you guys really believe in your product. Your name is linked to your site now, so if anyone wants to check out more info, they're welcome to.

    • profile image

      Bar's Products 

      8 years ago

      Hi. We're Bar's Products, makers of Bar's Leaks and Rislone. Saw this discussion and wanted to throw our hat in the ring.

      Though what you're saying in terms of negative effects this may be true for some products, it certainly is not for the majority of our stuff. In fact, we have items which actually *promote* heat transfer. This is beyond our Liquid Aluminum product which has the Xtreme Cool water-wetting agent; this is also true for our regular stop leak products.

      Our stuff works in two ways to accomplish this.

      There are millions of tiny particles in the regular Bar’s Leaks Radiator Stop Leak which increase the surface area and allow the cooling system to carry and disperse more heat. Second, we have our cleaning agent in our regular product which includes a host of ingredients specifically designed to keep the cooling system walls clean so they can efficiently transfer heat. Dirty walls don't work.

      If you'll pardon a little tiny bit of advertorial, we think that if it could be explained exactly how a good radiator stop leak works and some real world “OEM” examples, that would dispel some of the myths about this category of chemical fixes. But the larger issue is there are, unfortunately, still a bunch of junk products in the marketplace (as you guys allude to), and that gives all good products in the market a bad name.

      Thanks for reading.

      BTW, if you have any comments/questions/concerns/good stories, please let us know. You can call us at 800-345-6572 x204. Ask for Fred.

    • Benjimester profile imageAUTHOR

      Benji Mester 

      8 years ago from San Diego, California

      Thanks very much for that info. That's really helpful. I agree that radiator stop leak is like a double edged sword. It can help you out of a pinch, but in the long run you'll be kicking yourself for not getting things fixed right the first time.

    • profile image


      8 years ago

      Benji from experience of having used this product from many different brand names many times I can attest that it only works on very minor leaks.

      Because of this most products will say on the label that if it shows no improvement after a couple applications then you are going to need to get it checked out by a mechanic.

      Over use of radiator stop leak can plug up your radiator fluid system through the engine,the water pump and thermostat and may cause damage to the engine as a result by not allowing it to cool properly.

      There are many expensive products that if not applied properly can also set in your engine coolant channels very quickly upon the first application like a brick and then you will really be up the creek.So it's very important to follow the directions to a "T".

      Depending on the type of radiator and where the leak is it may be repairable,but in most circumstances and with most radiators being plastic these days you are usually better off to replace it. If however it is a metal radiator and you can find the leak easily after removing the radiator then you can sometimes cram the hole full of something like JB Weld or a similar product and it will block off the leaking channel.

      This is not recommended for a long term fix though as it does cut down the cooling ability of your system.


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