The engine cylinder head gasket seals the cylinder head to the engine block. It is responsible for:

1. Containing the high pressure created by the combustion process in the cylinders. Without it, the engine would not run.

2. Sealing the coolant passages between the block and head. This prevents coolant and oil from mixing which can damage the engine.

3. Ensuring even compression in all cylinders. If it fails, it can lead to loss of compression in one or more cylinders and reduced engine power.

4. Allowing for efficient heat transfer from the cylinders to the coolant. It must withstand high heat but also dissipate it properly.

5. Withstanding high stresses, pressures and surface sealing requirements in the engine. It is a critical component in engine operation.

When do you need to replace

The head gasket should be replaced if it fails or shows signs of issues. Some symptoms that indicate a blown or failing head gasket include:
•Overheating - Combustion gases can leak into the coolant system, raising engine temperature.
•Oil in coolant - A breach in the gasket can allow oil and coolant to mix. You may notice a milky color in the coolant or coolant in the oil.
•Coolant in oil - Similarly, a leaking gasket can allow coolant into the oil system, which is also problematic.

•Engine misfiring - Compression loss from a damaged gasket can lead to misfiring cylinders and a loss of power.
•Visible damage - You may see visible damage to the gasket itself, especially between cylinders.
•Excessive exhaust - Combustion gases blowing through a hole in the gasket into the exhaust system will increase exhaust temperature and pressure.
•Overpressurizing - Cylinder pressures can escape into the coolant or crankcase, damaging hoses, seals and more.
If any major issues with the head gasket are suspected, it is best to have it checked by a mechanic as soon as possible. Continuing to drive with a blown head gasket can lead to serious and expensive engine damage. Replacing a head gasket often requires removing both the cylinder head and engine block, so catch any problems early.