The cylinder head gasket is an essential component of a fuel engine. It ensures that the pressure created by igniting the fuel vapor through the spark plug stays inside the combustion chamber.
The combustion chamber contains pistons, which need a lot of pressure to ensure that they continue to burn correctly.
Oil and coolant are equally essential tasks, but they cannot be mixed to perform tasks effectively.
The cylinder head gasket keeps the chambers separate to avoid mutual fluid contamination.
The head gasket seals the engine’s combustion chamber and allows oil and coolant to circulate, as well as the combustion portion of the engine.
This allows the vehicle to fabricate enough power to move forward and prevents harmful gases from escaping from the combustion chamber by directing it through the exhaust system.
The head gasket of modern vehicles is made of several layers of steel material interwoven with elastomer, which makes them more durable.
Vehicles manufactured in the past were fitted with either graphite or asbestos gaskets.
Today’s head gaskets are better because they are less prone to leaks and pose little to no health risk than asbestos gaskets.
Purpose of the Head Gasket
Inside the water-cooled internal combustion engine, three fluids move between the engine block and the cylinder head:
- Combustion gas (unburned air-fuel mixture and exhaust gas) in each cylinder
- The water-based refrigerant in refrigerant lines
- Lubricating oil in oil galleries.
Proper engine operation requires that none of these circuits leak or lose pressure at the junction of the engine block and cylinder head. The head gasket prevents these leaks and pressure drops.
Types of Head Gaskets
- Multilayer Steel (MLS): Most modern engines use MLS seals, which consist of two to five (usually three) thin layers of steel interspersed with elastomer. Steaming surfaces are typically coated with a rubber coating, such as Viton, which adheres to the engine block and cylinder head, while the internal layers are optimized for elasticity.
- Solid Copper: Solid copper foil usually requires a special treatment called an o-ring, which places a piece of wire around the bounds of the cylinder to bite into the copper. When this is done, the copper gaskets become very durable.
- Composite: an older design is more prone to deflation than newer designs. Composite gaskets have traditionally been made from asbestos or graphite, but asbestos gaskets are becoming less common due to health concerns.
- Elastomer: This type of head gasket uses a steel center plate with silicone rubber balls to seal in oil and coolant. The holes are closed in the usual way with rolled steel fire rings. It was used in the Rover K series engine.
- O-ring: these seals are mainly made of steel or copper. They can be reused and, when used between properly prepared flat surfaces, create the most excellent clamping pressure due to their significantly smaller area than other types of joints.
What Causes a Head Gasket Explosion?
Engine overheating is the most repeated cause of cylinder head gasket breakage or damage.
High engine temperatures are always caused by a lack of coolant inside the radiator, generally due to a leak.
Depending on the material, some joints will likely weaken sooner than others. For example, aluminum expands faster when heated.
Metals with a higher thermal expansion rate are more sensitive to heat. Higher temperatures can change the shape of the object, which will cause unfavorable results.
The development and deformation of the cylinder head under the influence of heat weakens its integrity and prevents a good seal of the head gasket.
When the head gasket melts, it is vital to repair it immediately. Continuous inspection of the vehicle with melted gaskets can cause severe and irreparable damage to the engine.
Since the gasket is used as a gasket, maintaining pressure is essential for engine power.
Once the seal is broken, it can no longer act as a seal and will allow pressure to escape, drastically reducing engine power – one of the few signs of a broken head. Also, oil and coolant hoses can leak where they shouldn’t be.
As coolant enters the combustion chambers, it mixes and dilutes engine oil, reducing the cooling capacity of the cooling system, which can cause the engine to overheat.
Symptoms of a Head Gasket
The engine relies on three essential fluids: fuel, coolant, and engine oil. If the seal is broken, all fluids can enter or exit the combustion chamber.
You may notice some or all of the following:
- Overheating is caused by a lack or reduction of refrigerant and by the entry of hydrocarbons into the cooling system.
- White, blue, or grey smoke indicates that refrigerant or oil has entered the combustion chamber.
- Loss of Power: A shortage of compression causes splashing, loss of power, and reduced fuel efficiency.
- Colorless Oil: Oil that looks like milk chocolate indicates that the coolant is mixing with the oil in the engine.
Head Gasket Failure
A leaking head gasket, often called a “shaped head gasket,” can cause coolant, flue gas, or both to leak.
Blue smoke from the exhaust indicates that excess oil is entering the combustion chambers.
White smoke from the exhaust means that coolant is entering the combustion chamber.
Head gaskets are classified as external or internal. External leaks are visible as coolant or oil on the outside of the engine (usually at the bottom).
An internal leak occurs when fluids enter the second circuit and can cause oil or coolant changes.
The first may be the presence of foam (caused by hydrocarbons) in the coolant expansion tank.
A coolant leak in the oil system can result in a mayonnaise-like substance in the oil, which is often seen on the oil filler cap or dipsticks.
However, the existence of this substance is not conclusive evidence of a head gasket malfunction, as the oil could also mix with the coolant in other ways.
Besides, the head gasket can fail so that the oil never comes into contact with the coolant.
Therefore, it isn’t possible to determine the condition of the head gasket definitively by inspecting the oil.
Coolant Leakage
If coolant enters the cylinder, combustion of the air-fuel mixture is compromised, reducing engine performance and often causing exhaust gases (white smoke).
This vapor can damage the catalytic converter. If a large quantity of coolant gets into the cylinders, the engine can be hydraulically locked, which can cause severe engine damage.
Combustion Gas Leakage
When the combustion gases leave the cylinder, there is a loss of compression, which can result in reduced power or improper operation.
If combustion gases enter the cooling system, they reduce its efficiency and can cause the engine to overheat.
In other cases, gases can seep into small spaces between the gasket and the cylinder head or engine block, trapping them until they are released when the engine is stopped. These gases then escape into the refrigerant and create air pockets.
Sometimes, these airbags can get stuck in the engine coolant thermostat, causing it to stay closed and cause further overheating, creating more spaces between the gasket and the engine.
Otherwise, these airbags can cause the engine to push the coolant into the expansion tank or overflow.
Diagnosis and Repair of Head Gaskets
Common methods of testing the head gasket for leaks are a compression test (using a pressure gauge), a leak test, or a chemical test to determine the hydrocarbons in the coolant.
The cost of a replacement component (i.e., the head gasket itself) is usually relatively low, but significant labor costs are involved in the replacement process.
The process of replacing and removing the cylinder head gasket is a tedious task.
