How To Use Blue Devil Head Gasket Sealer [With Or Without Radiator Cap]?

Is there a leak in your head gasket, and you’d like to try to fix it with a BlueDevil Head Gasket Sealer? Do you want to know how to do it with or without the radiator cap? You’ve come to the right place, for we have researched this question, and we have the answer for you.

Here is a summary of the steps to use BlueDevil Head Gasket Sealer to fix your gasket problem. This is for a system with a radiator cap.

  1. Wait until the engine is cold.
  2. Flush the cooling system.
  3. Remove the thermostat.
  4. Remove the radiator cap.
  5. Fill the cooling system with water.
  6. Set the car’s heater to the maximum.
  7. Start the engine and let it idle.
  8. Slowly pour BlueDevil into the radiator.
  9. Reinstall the radiator cap.
  10. Let your car idle for 50 minutes or more.
  11. Stop the engine.
  12. Let the engine cool once more.
  13. Drain the cooling system.
  14. Reinstall a new thermostat.
  15. Fill the cooling system with a compatible coolant.

Let’s talk more about fixing your head gasket with BlueDevil Gasket Sealer in the succeeding sections. Learn more about the head gasket in the sections below.

Read on!

Why do you need to seal the head gasket?

The head gasket’s purpose is to create a joining seal between the two main divisions of the engine—the engine block and the cylinder head.

The area where the fuel and air mixture undergo the highest pressure is also where the cylinder head and the engine block commonly meet. Not all engines have this configuration, although the majority do.

This is where the head gasket is most needed—to create a seal that can keep the pressure within the combustion chamber.

Additionally, the head gasket is responsible for making sure that the coolant and oil that travels around the engine don’t leak into the combustion chamber and mix with the fuel and air mixture. Oil or coolant in the combustion chamber will dilute the air and fuel mix, causing it to produce less power.

How much BlueDevil Head Gasket Sealer should I use?

You need to pour all the contents of an entire bottle slowly into your radiator. This will ensure that the engine gets enough BlueDevil to seal any leaks within.

1 bottle of blue devil head gasket sealer

Can you pour BlueDevil into the coolant reservoir?

If you check the usage instructions at the back of the BlueDevil head gasket sealer’s bottle, it states that the BlueDevil should be used on the radiator.

Thus, for best results, you should not pour it into the coolant reservoir.

How to use BlueDevil Head Gasket Sealer?

Here are the complete steps that you can follow to use BlueDevil to seal your head gasket.

short-block-installed-cylinder-head-gasket, How To Use Blue Devil Head Gasket Sealer [With Or Without Radiator Cap]

Preparing Your Car

  1. Park your car on a level and solid space. It is best to park it in a well-ventilated area because you will need to let it run for almost an hour.


    • Make sure that your car has enough fuel in it to run idle for an hour or so.
    • Moreover, your car mustn’t stall during the entire process. Thus, your alternator or car battery must also be up to the task of running idle for more than an hour.
  1. Activate your parking brakes.
  2. Place your car’s transmission in Park(P).
  3. Let the engine cool completely.

Draining The Cooling System


  1. If you need to jack up your vehicle before you can get under it, follow the steps below. Otherwise, skip to the next step.
    • Jack up the front of your vehicle at the jack-up point.
    • Place a jack stand on the jack-up point behind both front wheels. For some vehicles, you will need to jack up from behind one front wheel at a time and then place the jack stand.
    • Give your vehicle a shake to test its stability.
    • Lower the jack, then raise it once more until it is just barely touching the jacking point. This is so it would serve as a backup in case one of the jack stands malfunctions.
  1. Press the radiator cap downward, keep it down, then rotate it counterclockwise. There will be a hissing sound after rotating the cap. Wait until the hissing stops.
  2. Remove the radiator cap.
  3. Slide under your car and locate the drain valve at the bottom of the radiator. If there is no drain valve at the bottom of the radiator, disconnect the bottom hose that goes to the radiator.
  4. Place a drain pan under the radiator. Position it under the drain valve or under the hose.
  5. Remove the drain valve cap and let the coolant drain out to the pan.

BIG RED Torin Steel jack stands are available on Amazon through this link.

Custom Accessories drain pan is available on Amazon through this link.

Removing The Thermostat


  1. Trace the lower radiator hose from the bottom of the radiator back to the engine. The end of the hose goes to a metal elbow joint with nut or bolt fasteners.
  2. Pull the hose off the metal connector.
  3. Remove the bolts or nuts that hold the elbow connector in place.
  4. Pull the elbow connector.
  5. The thermostat is inside the elbow connector. Remove the thermostat. If the thermostat is failing, it could break when you remove the connector.
  6. Reconnect the elbow connector and fasten it with a bolt or nut.
  7. Reconnect the radiator hose to the elbow connector.

Flushing The Cooling System

car coolant flushing cooling system

  1. Reconnect the drain valve cap or hose.
  2. Remove the radiator cap.
  3. Pour distilled water into the radiator until it is full. You can also use a cooling system cleaner instead of distilled water.
  4. Replace the radiator cap.
  5. Start the engine and let it run for 10 to 15 minutes. This will let the distilled water rinse the inside of the cooling system.
  6. Turn off the engine.
  7. Disconnect the hose or remove the drain valve once more.
  8. Drain the cooling system of the distilled water.

Prestone AS105 cooling system cleaner for the radiator is available on Amazon through this link.

Applying The BlueDevil Head Gasket Sealer

  1. Reconnect the drain valve cap or reconnect the hose once more.
  2. Remove the radiator cap.
  3. Pour distilled water into the radiator. Do not fill the radiator with distilled water. Leave enough space for the BlueDevil.
  4. Start the engine and let it idle.
  5. Set the heater and the fan to their maximum setting.
  6. Slowly pour the BlueDevil into the radiator. Make sure you are in a comfortable position when pouring the BlueDevil.
    • If the radiator doesn’t have a radiator opening, disconnect the topmost radiator hose and pour the BlueDevil head gasket sealer through there.
    • Raise the hose slightly upward so that the opening is slightly higher than the radiator.
    • It is important to pour the BlueDevil in really slowly.
    • It should take you around thirty seconds to pour in half of the contents and a full minute to completely empty the bottle of BlueDevil into the radiator.
  1. Replace the radiator cover and let the engine idle for at least 50 minutes.

Completing The Application Of BlueDevil

  1. Turn off the engine.
  2. Let the engine cool once more.
  3. Remove the radiator drain valve cap.
  4. Let the distilled water drain out of your car.
  5. Replace the drain valve cap.
  6. Disconnect the hose from the elbow connector.
  7. Remove the bolt or nut that keeps the elbow connector in place.
  8. Reinstall the thermostat. You must reinstall it in the right position. The rounded side of the thermostat points to the radiator, and the long side points to the engine.
    • Look for the small toggle switch on the thermostat.
    • This switch should point up to the engine to make it easier for air to escape.
  1. Insert the pointed side of the thermostat into the engine with the toggle switch pointing upwards.
  2. Install the elbow connector over the thermostat.
  3. Reinstall the bolts or nuts to keep the elbow connector in place.
  4. Insert the radiator hose.
  5. Release the jack stands and carefully lower your vehicle.
  6. Refill your radiator with a compatible coolant or antifreeze until it gets to the full level.
  7. Start your car’s engine.
  8. Set the heater and the fan to the maximum.
  9. Add more coolant as the coolant level drops. The thermostat will start to allow the coolant to circulate in the engine once the engine reaches the ideal temperature. Once the coolant circulates the engine, the coolant level on the radiator will drop. Keep adding coolant until you reach near the maximum level on the reservoir.
  10. Add an antirust coolant additive to help protect the radiator and the rest of the parts of the cooling system.
  11. Once the coolant level stabilizes, stop the engine and cover the radiator.

Prestone’s super radiator anti-rust is available on Amazon through this link.

Can BlueDevil clog a radiator?

According to the manufacturer’s website, BlueDevil does not contain any fibrous materials. Thus, it will not harm the components of cooling systems like the radiator.

Can BlueDevil mess up the thermostat?

BlueDevil can mess up the thermostat. Its sealing ability will clog up the thermostat’s system.

This is why it is important to remove the thermostat during the application process. Once you finish flushing the system, reinstall the thermostat.

It is a good idea to check the thermostat after a few weeks of running your car after the application of BlueDevil.



BlueDevil’s head gasket sealer can seal leaks in the head gasket of your car. However, you will need to flush the coolant, making sure the cooling system is clean before you can use it.

If you enjoyed reading this article, you might find the articles below equally enjoyable to read:

Should I Use Copper Spray On My Head Gasket [& How To]?

Most Common Problems After Head Gasket Replacement – What To Look For?

Share this article

Leave a Reply

Your email address will not be published. Required fields are marked *