How Can I Check For A Blown Head Gasket?

Blown Head GasketThe best way to check for a blown head gasket is to know the symptoms it creates in your vehicle.  Many of the symptoms a leaking head gasket creates can be confused with other problems, so it’s important to diagnose the problem correctly and look for multiple symptoms.

Symptoms of a Blown Head Gasket:

  • Over heating
  • Low Coolant levels
  • Coolant leaking from the engine
  • White smoke from the exhaust
  • Sweet smell while driving

There are varied and multiple blown head gasket symptoms because the head gasket has a lot of jobs.  The head gasket sits between the engine block and the engine head.  Coolant has to flow in and around the head and the block and it is kept in the coolant passage by the head gasket.  Also, the head gasket is responsible for keeping the combustion gases in the combustion chamber and out of the coolant passages.  Head gasket failure can therefore result in a leaking of coolant outside the engine to the atmosphere, and leaving drips or puddles under your car, or leaking of coolant into the combustion chamber causing white smoke from the exhaust and a sweet smell.

Having multiple of the above symptoms at once is a good indication that you have a blown head gasket, however, you can check for sure.  If you have an external leak with puddles and drips, you can check to see if the coolant is coming from in between the head and the block (just under the exhaust manifold).  You may need a mechanics mirror, available at your local auto parts store, to be able to see the affected area.  If you Blown Head Gaskethave an internal leak with white smoke and a sweet smell, you can purchase a Combustion Leak Test Kit from your local parts store.  The Combustion Leak Test Kit will test your coolant for the presence of exhaust gases, proving there is a breach between your combustion chamber and coolant passages.  Lastly, you can perform a cooling system pressure test to detect a leak, but the equipment for this test is expensive and it will only prove there is a leak, and not necessarily the location.

Once you are confident your head gasket is leaking, head to your local AutoZone, NAPA, Advance Auto Parts, Car Quest, O’Reilly, or Bennett auto supply or Prime Automotive to pick up a bottle of BlueDevil Head Gasket Sealer or Pour-N-Go.  BlueDevil Head Gasket Sealer is activated by the temperature differential at the leak point so it only is activated where there is a leak and will not clog or harm the rest of your cooling system.  You can also purchase BlueDevil Head Gasket Sealer directly from BlueDevil here: Head Gasket Sealer

BlueDevil Head Gasket Sealer

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16 responses to “How Can I Check For A Blown Head Gasket?

  1. So I bought blue devil and without opening it, overnight 75% of it evaporated or spilled. I guess the seal was broken. Its cool that they are sold with broken seals and you pay 50 bucks to not even be able to see if it works.

  2. Have a 4.3 liter, inboard/outboard, GMC motor.
    The coolant is not in a closed system, but circulates H2O surrounding boat as a coolant. Will BlueDevil head gasket sealer work on this motor?

    1. Nick-

      We have had success using BlueDevil Head Gasket Sealer with marine applications in the past. The key is that you are able to circulate the same body of water for the recommended 50 minute idle; using a bucket or barrel would accomplish this. The other need is that the water will heat to at least 150 degrees during that run.

      Feel free to contact us at 888-863-0426 with any further questions.

      Thank you!


    1. Carl-

      Typically, combustion/exhaust gases getting into the cooling system would cause the vehicle to overheat. However, if the gases are only entering intermittently, or the system is not losing water/coolant at an extreme rate, the temperature may simply fluctuate and may take longer to overheat, if it does so at all. Feel free to contact our technical support line at 888-863-0426 with any other questions.

      Thank you!


    1. Michael-

      Thank you for asking about your Chevy Tahoe. Yes, the BlueDevil Head Gasket Sealer would be able to seal that kind of a leak. To give yourself the best overall chance of BlueDevil working successfully is to remove the spark plug from the cylinder with the leak; this will be the spark plug from the cylinder with the low compression reading. If you are not sure which one that is, you may pull all of the spark plugs and will notice one will have a white-crystal-like substance on it and/or may look dirty; this is the plug you should pull. Leave the plug out for the 50 minute idle in order to relieve the pressure from building up and thus allowing the product to seal properly.

      Thank you!


  3. I am having a problem with a 350 chevy tbi engine. It started running 210 after I changed a bad water pump and a weeping radiator. Changed the thermostat twice, did a compression test and a leak down test, both were within specs. Changed the dash gauge and sensor and still ran hot. Tried a new fan clutch, no change. It has 50000 miles and always ran at 195 before the new pump. Can your product help me?

    1. Mario-

      Thank you for asking about your Chevy. Is it still lowing water/coolant after replacing the water pump and weeping radiator? Based on your description, it does not seem like the vehicle has any tell-tale signs of a blown head gasket. Have you noticed any bubbling or boiling over in the radiator or overflow? Please contact our technical support line at 888-863-0426 so that we can get a little better understanding of the vehicle’s condition and be able to make any appropriate recommendations.

      Thank you!


  4. I Have a Cummins 450 Diamond / 6cta diesel. Recently had to remove the turbo on stbd. to replace a torsion coupling in gearbox. Its the only thing we did before experiencing the current problem. Installed a fresh gasket on turbo, and all new hoses. Engine always ran at 160 degrees and matched port engine for years.
    Just noticed a raise approx. 1 1/2″ in the coolant tank while engine is running, and temp about 5-8 degrees hotter that it used to run, Absolutely no leaks from engine, and after the engine cools down, the coolant level goes back down in the tank to original level. Replaced the radiator cap already. Any ideas on what to do next?

    1. Peter-

      Thank you for asking about your Cummins 450 Diamond. Based on your description, it sounds like coolant may be being forced back into the overflow tank. If that’s the case, it’s possible you have combustion/exhaust gases pumping back into the cooling system. Another possibility is an air pocket. Try bleeding the system to remove the excess air. If that doesn’t help, we’d recommend performing a block-dye test to check for combustion/exhaust gases.

      Hope this helps!


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