How Do I Fix a Leaking Freeze Plug?

As vehicles have gotten more and more advanced both consumers and environmentalists have required them to get increasingly more efficient, produce more power, use less gas and produce less harmful emissions products.

Leaky Freeze PlugOne major advancement in the efficiency of the internal combustion engine was the water cooling system.  The efficiency of an internal combustion engine is proportional to the compression ratio, meaning the higher the compression ratio the more efficient the motor will be.  The difficulty is that a higher compression ratio will produce higher combustion and exhaust temperatures.  These higher temperatures if not properly controlled can cause damage to the engine components like the piston rings and valves.  Adding a water cooling system allows for the excess heat to be removed and the engine to safely operate with a higher compression ratio.  Air cooled engines were used to some extent in older vehicles like the Volkswagen Beetle and the Porsche 911, but today are mainly used in motorcycles to reduce weight and complexity.

In modern cars, cooling systems have gotten even more complicated to include your radiator, the engine block, a heater core and the hoses and lines connecting them all together.  Many cars also have other cooling devices associated with the cooling system like a transmission cooler or oil cooler.

All of these cooling components help the engine in your car run smoothly and more efficiently.  If an engine is designed to be water-cooled it is designed to have higher operating temperatures, higher compression ratios and produce much more heat.  This reality makes it essential to any water cooled motor to ensure the system is operating properly or it could easily render the vehicle inoperable.

The difficultly with operating a water-cooling system in your vehicle is that most vehicles at some point will be operated in a climate that has temperatures below freezing.  When water freezes and turns from a liquid to a solid it actually expands, or increases in volume.  This increase in volume causes many problems around the world today, like frost heaves in the road and broken water pipes in your house.  The cooling system in your car is susceptible to the same problem if it were to contain pure water.  The best solution to this problem is the add antifreeze to water lower the temperature at which it will freeze.

Leaking Freeze PlugWhen water freezes, it can exert well over 10,000 lbs per square inch of pressure on the container it is in.  In the case of the water jacket in your engine block, this is more than enough pressure to cause it to crack destroying your engine.  The engine in your vehicle also has a secondary line of defense against freeze damage, freeze plugs.  Freeze plugs are usually aluminum or brass plugs pressed into holes in the water jacked of your engine block.  In some cases, as the water freezes and expands in your block, the freeze plugs will push out relieving the pressure of the freezing water and partially draining your cooling system.

A leaking freeze plug can be an indication that your cooling system did or came close to freezing.  When a leaking freeze plug is found, the engine should be checked for damage and antifreeze checked for the proper mixture and freezing point.  However, freeze plugs can also start to leak over time simply due to the heating and cooling cycles of driving your car.

Leaking Freeze Plugs

Replacing a freeze plug can be a frustrating job since it requires the draining and refilling of your cooling system, and the old plug will likely have to be destroyed to be removed.  Instead, add BlueDevil Pour-N-Go to your cooling system.  BlueDevil Pour-N-Go is incredibly simple to use and will permanently seal a leaking freeze plug without having to drain and refill your cooling system or ever crawl under your vehicle.  BlueDevil Pour-N-Go uses a chemical that reacts to the temperature differential at the leak point forming a permanent bond that contains no particulate matter so it is safe for your entire cooling system.

BlueDevil Pour-N-Go Head Gasket Sealer

Pick up BlueDevil Pour-N-Go at your local auto parts stores like O’Reilly Auto Parts, NAPA, Advance Auto Parts, Autozone, CarQuest Auto Parts, Bennett Auto Supply, Pep Boys and Prime Automotive.  You can also purchase it directly from BlueDevil here: Pour N Go Head Gasket Sealer

Pictures courtesy of: and


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9 responses to “How Do I Fix a Leaking Freeze Plug?

  1. Aloha
    I have a pin size hole in my core plug (freeze plug) it’s leaking.
    I tried the bars leaking with copper in it and its just leaking out of the
    Core plug. The location of the core plug is located behind the engine and
    Fire wall. How can I take on this project with your product step by step?
    I Am very intrested on trying it but 63.00 in hawaii it’s pretty pricey. I guess
    This would be my last step because i bought it for 500 bucks and not
    worth going through the labor work or paying a mechanic. Please
    Advise. I have pictures of the leaking freeze plug upon request.
    Michael Morgan

    1. Michael,

      Please give our tech line a call for some additional support. Our BlueDevil Head Gasket Sealer (Part #38386) should do the trick for you. It does require a full radiator flush prior to installation. Call 1.888.863.0426 at your convenience and we can assist with any installation questions.


    2. Hey Dealing with a freeze plug problem would Like To See The pictures you have of a Leaking freeze plug if You still have, I see that you posted this back 2013 … but if You still have, I would appreciate seeing them, so that I can compare to what I See leaking on my own car ……. Thanks for your time

      P.S. Also one question, If a freeze plug is leaking could that cause a car not to start due to all the antifreeze that comes right back out of the car once filled ?

  2. Im really assured that your product has what it takes to fix my freeze plug problem and im going to go purchase some of your product later this morning. Its ridiculous how some merchants, mechanics rather rip you off, than resolve such car catastrophe.
    Sincerly, Mr. Larry White

    1. Not all of us do, some yes but not all mechanics do. The right way to fix anything that’s broken or worn out is to replace it. I will try this product as well and if it does I’ll swear by it. Good luck with your issue as well.

  3. I have a 98 Ford ranger and I have a freeze plug leaking rather profusely like in the above picture. I pour water in and it starts flowing out the freezer plug, which is located behind the motor mount. Would the radiator and block sealer stop a leak like this?

    1. Kyle-

      Based on the extremity of your leak, it is larger than what BlueDevil Radiator & Block Sealer is intended to fix. The product would be lost prior to it being able to create a seal due to how quickly the coolant is being lost. Your only solution may be to have the freeze plug replaced.

      Thank you!


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