The head gasket acts as a sealer between the cylinder head and the engine block. Apart from sealing the combustion chamber, it allows the car to maintain proper compression that is crucial for maintaining engine efficiency. Overheating, pre-ignition, poor design- are the typical causes of head gasket failure in a car. Depending on the cause, the potential damage can be fairly extreme. You must keep the gasket inspected and replace the gasket whenever needed in order to save your SUBARU from the scrapyard.