Why Does a Blown Head Gasket Smoke?


blown head gasket smoke, exhaust smokeOne of the telltale symptoms of a blown head gasket is white smoke from the exhaust.  It’s important that the smoke is white because blue or black smoke can indicate a rich running engine or an engine that is burning oil.  It’s also important to note that white smoke can also come from your exhaust on very cold wet days or right when you start up your engine so be sure to learn the other symptoms of a blown head gasket so you can be sure of what the problem is.

A vehicle with a blown head gasket will smoke due to the introduction of coolant into the combustion chamber.  Normally the only thing that is in your engine’s combustion chamber is air and fuel which, when burnt efficiently, should produce water and gas byproducts.  The introduction of the coolant adds water and glycol to the mixture. Now, the coolant doesn’t burn as part of the combustion process but it will vaporize. This water vapor is what you see as smoke from your exhaust.  Along with the white smoke, there will be a sweet smell from the glycol and other additives in your coolant.

Besides the smoke and smell from a blown head gasket, the addition of water in the combustion mixture will also lead to an excessively clean combustion chamber.  If you suspect a blown head gasket, you can often remove the spark plug and use a boroscope to examine the top of the piston. The coolant will have a cleaning effect and the position will often be bright metallic rather than the dingy black a normally used piston will have due to the carbon build-up.

While a blown head gasket will clean your combustion chamber, it allows your cooling system to get extremely dirty.  Normally your cooling system is closed to dirt and debris and stays very clean. When your head gasket blows exhaust gases get into your cooling system your coolant will become extremely dirty very quickly and will often get and oil slick floating on the top of it in your radiator and in your overflow bottle.

If you’ve got all 3 of these symptoms together, the smoke, the clean combustion chamber, and extremely dirty coolant then you’ve got a blown head gasket.  If the hard part repair doesn’t make sense for your vehicle, consider using BlueDevil Head Gasket Sealer to stop your head gasket leak and keep your vehicle driving!

You can pick up BlueDevil Head Gasket Sealer at one of your local auto parts stores like:

  • AutoZone
  • Advance Auto Parts
  • CarQuest Auto Parts
  • NAPA Auto Parts
  • O’Reilly Auto Parts
  • Pep Boys
  • Canadian Tire
  • Walmart

Pictures Provided By:

exhaust_smoke.jpg – By Stefan_Redel – Licensed by Getty Images – Original Link

BlueDevil Products can be found on Amazon.com or at AutoZone, Advance Auto Parts, O’Reilly Auto Parts, NAPA, and other major auto parts retailers.

6 responses to "Why Does a Blown Head Gasket Smoke?"


  1. Carl on November 25, 2020 at 11:33 pm

    How long does Blue Devil head gasket sealer usually last

    • BlueDevil Pro on November 30, 2020 at 9:40 am


      The BlueDevil Head Gasket Sealer carries a very high success rate. Once the product seals, it would be a permanent seal. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  2. James on July 2, 2021 at 3:10 pm

    Before using blue devil do you change the fluids ? Coolant and do an oil change ?

    • BlueDevil Pro on July 6, 2021 at 8:16 am


      You would want to flush the cooling system prior to using the BlueDevil Head Gasket Sealer. If you are getting water/coolant into the oil, we recommend changing the oil before and after the procedure. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


  3. Paul on November 21, 2023 at 1:54 am

    How do you know which of the four different B.D. head gasket/cracked block sealing products is the best one to use in a particular application? Wish you had a comparison chart on your website to aid in that selection process.

    • BlueDevil Pro on November 21, 2023 at 8:31 am


      You may use either of the two Head Gasket Sealers or the Head Gasket Repair. The Pour N Go Head Gasket Sealer is an easy to use, less concentrated formula that does not require the removal of the thermostat or a flush of the cooling system prior to use. BlueDevil Head Gasket Repair is also an easy to use product that is 2x more concentrated than the BlueDevil Pour N Go Head Gasket Sealer. Whereas the “Mechanic Approved” requires both the removal of the thermostat and a flush before applying the product; the 32 ounce is the strongest formula.

      The product with the yellow label will give you best overall results as long as you can remove the thermostat and flush the system prior to use. However, if the thermostat is difficult to remove or you would rather not then you can always use the “Pour N Go” Head Gasket Sealer or Head Gasket Repair. Any of the products may be added with fresh antifreeze or water.

      Thank you!


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