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How to Repair a Blown Head Gasket: Are They Worth Repairing?

How to Repair a Blown Head Gasket
Written by Nick Steiner

Once you’ve blown a head gasket, it could be the end of your car. You will need to figure out what your next step will be. Here we look at what a head gasket does, signs the head gasket needs replacing, what causes a head gasket to blow, and how to repair a blown head gasket.

Anatomy of a head gasket

Today’s head gaskets have multi-layers of steel, with the middle layer being the thickest. The thinner outer layers have a Viton covering. Viton is a chemical-resistant polymer that is rubber-like and resistant to extreme heat. The Viton-covered gasket is a seal between the engine block and the cylinder head—the head gasket seals in the coolant, oil, and engine compression separate from the cylinders.

The whys and hows of the head gasket

As a seal, the head gasket is a none moving part, but without the head gasket, your engine is worthless.

In the cylinder head, the lubricated pistons pump hundreds of times a minute as the sparks created by the internal combustion system ignite the sparks that heat the air and fuel that explodes to pump the pistons. If there is an oil leak, the pistons won’t pump. If the ignition space fills with oil, it dampens the explosion.

The head gasket is made to withstand the heat and pounding on one side and immense pressure from scorching air and pressure on the other. Any shrinking, slipping, corrosion, or cracking of the head gasket caused by this pounding, chemical attacks, pressure, and heat causes critical stress and eventually will ruin the engine. While head gaskets should last the life of your vehicle, that does not always happen.

While the holes in a head gasket can be confusing, they all serve a purpose. The smaller holes allow coolant to pass through. Most medium holes are to bolt the engine block and cylinder head together, and the larger holes are the piston pump’s actual cylinders.

Signs Head Gasket May Be Blown

Milk colored oil

When coolant mixes with oil, the oil looks tan or milky. As you remove the oil cap, you will see this milky film on the cap and in the oil.

Bubbling coolant

If air gets into the coolant, you may hear bubbling like boiling water in the coolant reservoir or the radiator. Bubbling antifreeze can blow the head gasket or cause leaking. If you hear this, DO NOT OPEN THE RADIATOR CAP UNTIL THE CAR HAS COOLED DOWN!

Smoke and water vapor from your exhaust

Coolant can invade the engine when your head gasket is faulty. This coolant invasion will cause water vapor or white smoke to exit your exhaust pipe.

Wet or fouled spark plugs

Once your head gasket is blown, gas, oil, and coolant can flood or foul up the sparks.

Overheated engine

Engines with blown head gaskets lose the ability to cool down while driving. If your vehicle should overheat, stop and turn off the vehicle to prevent extreme engine damage and figure out why the car is overheating. NEVER open the radiator cap when the engine is overheating. As you open the radiator cap, it will result in facial burns from the scalding coolant geyser!

Coolant and oil leaks

The head block may leak coolant and oil if the seal on your head gasket is lost. Look for oil and antifreeze under your vehicle and on the engine block and head.

Misfiring engine

When the engine fires properly, the air/fuel mix is perfect, and the spark hits it at the precise time to run the engine. If the fuel/air mix is off or the spark is out of timing, the engine will misfire.

What Causes a Blown Head Gasket?

Several of the following issues can result in a blown head gasket.

  • Overheating

Pressure from heat causes the engine to overheat (like a pan of boiling water), creating extra pressure on the head gasket and the head. When the motor gets too hot, the gasket blows.

  • Cracked or warped head or block

The same heat that causes the engine to overheat can cause heat damage to the cylinder heads and the engine block. Aluminum engine parts aren’t as strong as steel and wear quicker, causing the heads to warp. Once they warp, the head gasket seal breaks, and the gasket is blown.

  • The head gasket gets old

After years of extreme heat, immense pressure, and movement in the head block, the head block loses the ability to stay sealed. These harsh conditions cause the seal to fail and the gasket to break down after constant use.

  • Poor installation

If the head gasket were installed incorrectly, it would be faulty from the start.

Testing for a blown head gasket

Testing the head gasket is the best way to determine if you have a small leak vs. a blown head gasket.

  • Leak tester for head gaskets

The leak tester detects a head gasket leak by sucking fumes from the radiator into the testing tube, turning the fluid from blue to yellow if combustion gas is present. You can buy these online and in auto part stores.

  • Antifreeze compression test

The hand pump tester checks the system by adding pressure to the coolant system or the radiator cap to ensure the pressure is in the acceptable range if the system doesn’t hold the pressure for 2 minutes, the system leaks. You can also purchase the Antifreeze Compression kit at an auto parts shop or online.

  • Radiator bubbling

Despite being a sign that the head gasket is blown, it is an effective way to see if the gases from the exhaust are escaping from the radiator. If you hear the bubbling, park the car and turn it off. Let the engine cool, then remove the radiator cap, and start the vehicle. If the coolant starts bubbling, the gasket is blown. Shut off the car and call a tow truck.

The Head Gasket Is Blown. Now What?

Once you’ve confirmed the head gasket is blown, a few things need to be considered.

Professional head gasket repair can cost anywhere from $1200 to $3500 plus the cost to repair the problem that blew the head gasket. Will it be cheaper to take the repair money and buy a new vehicle? Does the car still have miles to go, and can you replace the engine? Is a new engine cheaper than repairing the head gasket? Do you have the money to pay for this? If not, where will it come from? These are just a few questions you need to consider.

While the options aren’t stellar, you have a few choices.

  1. You can pay for the repairs.
  2. Buy a new engine and install it yourself or have a professional install it.
  3. Purchase a new vehicle.
  4. Repair the head gasket yourself.

Changing a head gasket step-by-step

Tools

  • Screwdriver
  • New head gasket
  • Pliers
  • Socket wrench
  • Torque wrench
  • Brake or parts cleaner
  • Clean rag
  • Drain pan
  • New antifreeze

Step 1: Find the negative battery cable on the top of the battery. Disconnect it by unscrewing the terminal connector and removing it.

Step 2: Disconnect the intake hose and remove the airbox.

Step 3: Loosen and remove the bolts on the compressor for the air conditioner. Remove the compressor, laying it on its side so you can get to the cylinder head.

Step 4: Unscrew the clamps that secure the hose for the water pump and remove it.

Step 5: Remove the bolts that secure the alternator, but leave the harness. You want to move the alternator without taking it off.

Step 6: Drain the radiator into a drain pan by removing the petcock underneath the radiator. Use a socket wrench or screwdriver if it is challenging to get the plug out. Once you drain the radiator, remove the radiator hoses. Then, disconnect the air conditioning lines.

Step 7: Now, you should see the head gasket. Check the car’s manual for the tightening and loosening order for the head gasket bolts. Follow the bolt sequence precisely as the manual says to remove the bolts.

Step 8: Once the head gasket is off, clean the cylinder head thoroughly to ensure the head gasket seats well.

Step 9: Put the head gasket in place and fit it correctly, then replace and tighten the bolts in the proper sequence. Check your manual for the specified torque before tightening the bolts.

Using the wrong torque could damage the head gasket!

Step 10: Reconnect all the parts in the same order you disconnected them to ensure all the hoses and lines are reconnected.

Step 11: Replug the radiator and refill it with coolant (if you don’t know how much to use, check the owner’s manual.) Start the vehicle and let it idle so it reaches operating temperature.

Step 12: Let the car idle another few minutes after reaching the operating temperature. Then shut off the car and check if the new head gasket is leaking.

About the author

Nick Steiner

Nick has been a car nut for his whole life as far as he can remember. His father was a car dealer who used to change and repair his cars himself. As a result, Nick had the opportunity to get around all sorts of cars and learned to get his hands dirty repairing vehicles from an early age.

Nick is a great fan of Japanese quality and German preciosity. His deep passion lies in older models that he believes have a flair that takes him back to his childhood. He also loves their durability and reliability when compared to the modern models.

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