How to Test for Blown Head Gasket

A head gasket is a ringed panel positioned between an engine block and the cylinder head in an automobile engine. It resists the pressure of the two surfaces rubbing, warping, shrinking and expanding while containing the coolant and the engine oil flowing through casting ports. The head gasket acts as a boundary that stops leaking engine fluids from getting into the cylinders. This makes it a crucial component of the combustion chamber. It also ensures the gas fumes ignited by the spark plug are contained within the combustion chamber. The pistons are also positioned in the combustion chamber. It is important to note that there is maximum pressure to keep the pistons firing effectively.

The head gasket functions as a corridor for coolant and motor oil and upholds the chambers’ separation to prevent the mixing of the coolant and motor oil. The two liquids serve a different function that is why they should never mix. Due to its location between cold and hot components of the engine, the head gasket withstands all temperatures ranging from the cooling system’s cold temperature to the combustion chamber’s high temperature. They are typically composed of copper or steel. However, some gaskets are made of asbestos and graphite, which are not very efficient. Lately, manufacturers are doing away with the asbestos, which are known to have negative effects on your health.

What Causes a Blown Head Gasket?

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The first cause is extreme engine temperature. When a coolant leaks, it causes insufficient cooler to flow through the radiator. The temperature in the engine will rise due to inadequate cooling effect.

When the rates at which the engine and the head gasket expand are different, a newly expanded opening is formed and cannot be sealed by the gasket head. This commonly happens on some automobiles that have an aluminum head gasket and an iron cylinder block. Similarly, some engines are manufactured with inadequate clamping force from bolt heads or heads likely to warp and fail.

What are the Signs of a Blown Head Gasket?


When an engine frequently overheats due to faulty fan, a clogged radiator or a coolant leak, you may be having a blown head gasket. Blown head gasket causes overheating of the engine. However, overheating of the engine due to coolant leak also causes a blown head gasket. Hot exhaust fumes can sip into the cooling system interfering with the cooling effects. The coolant can sip into the cylinder and get burnt as steam, both cases resulting in overheating. If you persistently drive a car with overheating issues, it may cause head warping of the alloy cylinder or the catalytic converter being damaged by the steam. This will significantly increase the cost of repair.

Loss of Power

A faulty head gasket enables the compressed fuel and air mixture to exit, resulting in reduced compression in the cylinder. Engine problems such as rough running or reduced engine power are often caused by reduced compression in the cylinder. A sound similar to an exhaust leak accompanies the loss of power.

External Leaks

If a head gasket between the oil and the water passage and the engine’s outside has failed, this can lead to oil or coolant leak. Leaking in the external parts may not present Itself as an immediate cause of the alarm and may be overlooked. Still, it takes too long before it is fixed; the level of the coolant will drop significantly and cause severe damage to the engine. Leaking oil may also sip into the hot exhaust, eventually resulting in acrid smoke and perhaps even fire.

White Smoke

White smoke from the exhaust that smells sweet billowing is an indication of the faulty head gasket. When antifreeze leaks through the gasket into the gas cylinder where it is burnt to steam during the combustion process, it produces a smoke an oil passage leak sipping into the cylinder, causing a bluish smoke after being burnt to steam. This kind of gasket malfunctions will enable combustion pressure to enter the oil breather system or the cooling system. If a radiator hose’s water outlet is blown off or out of place dipstick, this may be the explanation.

Oil Contamination

A milky sludge below the oil filter cap or on the dipstick is a clear indication of the blown head gasket. This oil contamination is caused by the coolant finding its way into the oil or the oil finding it’s way into the coolant. This is not a definite proof of a faulty head gasket, but if all the other symptoms accompany it, then it is a clear indication that the engine is in trouble and has to come out for further inspection. Driving with antifreeze contaminating your oil rapidly ruins the bearings of an engine. To fix this issue, you will need engine oil flush and an oil filter replacement. The engine’s bottom will then be disassembled entirely to ascertain that the engine bearings have no damages and are totally free of contaminated oil.

How to Test for a Blown Head Gasket

The Coffee Color Test

Before you start this test, make sure that your engine is cold. Please take off the oil filler cap and inspect it for any coffee-colored liquid forming around or inside it. The coffee-colored liquid’s presence indicates that the coolant mixed with the oil, which implies that the head gasket failed to keep the liquids separated. Confirm if the dipstick has a similar color after dipping it into the engine oil. After confirming that the results test positive for the faulty head gasket, you will proceed to repairs; however, if you do not observe anything, move on to the next step as this test is not always conclusive.

The Spark Plug Test

Faulty head gaskets are manifested through leaks. Please take out your spark plug to be examined as leaks are mostly seen in them. Pressure the cooling system after you have taken out the spark plug. While you are carrying out your examination, crank the engine. If the spark plug hole begins sprinkling out, then there is coolant inside the holes. This is a clear indication that you have a blown head gasket.

The Bubbles Test

A faulty head gasket enables combustible gases to get into the cooling system. Suppose you discover bubbles of air in your expansion tank or radiator. Take any safety precaution necessary while carrying out this test as the coolant is at risk If erupting from the radiator.

To check out for bubbles, warm your engine after removing the radiator cap. You will discover bubbles in the tank if you have a bad head gasket. To aid this test, try using a combustion leak tester kit.

Hydrocarbon Test

Having the right working tools is an essential part of testing for a blown head gasket. Correct tools will save you time and energy. A gas analyzer is one of the tools that will make things easier for you during this process. It is part of an emission reading machine that detects the number of hydrocarbons present in the engine. If it is too much, then you probably have a blown head gasket. Carrying out this test at a repair shop with the assistance of a professional is highly recommended.

  1. Take off the cap and fit in the gas analyzer’s exhaust probe.
  2. Place your hand above the exhaust probe to ensure that it is getting adequate gas for analysis.
  3. There shouldn’t be any coolant in your analyzer as it is only supposed to read gas but not liquid.
  4. Most cars still have pressurized caps, be cautious if you’re working with them.
  5. It is time to have your head gasket fixed if the hydrocarbon goes beyond 100 after checking your reading.
  6. Carry out the test at least three times and crank up the engine for more accurate readings.

The Compression Test

Just in case all the tests fail, do not stop just yet. It’s common for the head gasket to blow in between two tanks. The space in the head gasket enables the combustion or contraction of one cylinder to drip into the other.

  1. Remove the spark plugs and manually bind the compression.
  2. For each cylinder, crank the engine while observing the readings on the compression tester.
  3. You are dealing with a blown head gasket if the two side by side cylinders read 0psi.

How to Repair a Blown Head Gasket

Find a negative battery terminal positioned at the tip of the battery and disconnect it.

Take out the Intake Airbox and Hose

  1. Remove the air conditioner compressed. You will have to take out numerous bolts. After freeing the compressor, lay it on the side to gain access to the head of the cylinder.
  2. Use a screwdriver to loosen up screws securing the clamp and then get the water pump hose disconnected.
  3. Take off the alternator. It is not necessary to remove the whole alternator harness.
  4. Drain radiator and take off the hoses. All the lines running to the air conditioner should be disconnected.
  5. The head gasket should be seen at this point. Carefully read the instruction from your service manual on the tightening sequence of the head bolts securing the gasket in position. This has to be done in the proper reverse.
  6. Take out the blown head gasket. Completely clean up the cylinder head to enable the new gasket (view on Amazon) to position well.
  7. Position the new gasket in place and position and firmly secure it with the bolts. A torque wrench will come in handy at this point.

Replace the Components

Put fresh coolant in the cooling system, turn the engine on and let it idle until operating temperature is achieved.

You Need to Know This About Your Blown Gasket

Most vehicle owners understand that a vehicle must be inspected and serviced from time to time, as referred to as routine maintenance. For those who don’t, the likelihood of problems that cause a damaged head gasket is extremely high. If the vehicle is not inspected routinely, small problems can escalate to major problems that are much more expensive to fix. This is also true for vehicles which sit for long periods of time.

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A lot of our readers have the Auto Maintenance and Repair Manual printed on their garage wall and 92% of them haven’t visited the auto repair shop in the last year because they know what to do to avoid problems. All it takes is giving your vehicle a little attention every few thousand miles and you’ll never spend money at the workshop again.

Preventing Head Gasket Failures

Repairing a head gasket involves intensive labor, even though the head gasket is inexpensive. The total cost of labor and repairs is significantly high, mostly on modern vehicles. Therefore, preventing the causes of a blown head gasket will save you quite a lot, both money and time.

Since faulty head gaskets are mostly caused by overheating or driving with an overheated engine for a long time, ensure that you regularly check your cooling system to ascertain that it is in good shape. If your car begins to overheat, stop, and allow it to cool down for not less than an hour and fill up the radiator before you proceed. To inspect the cooling system, watch out for leaks, and ensure that the radiator is functioning well. The thermostat should open up correctly, and the coolant is up to the required level. The fan should be in good shape with all its blades intact, and to increase efficiency, it should have a shroud surrounding it.

Do the scientific tests to detect combustion gases present within the cooling system, if you think you have a faulty head gasket. The test will indicate if there was leakage of the compression into the cooling system. If there are bubbles in the coolant when you start the car after taking off the radiator indicates the presence of gases.