Parts for your 2005 Subaru Impreza-Head gasket

2005 Subaru Impreza head gasket — what it does and how to look after it

Yes, the 2005 Subaru Impreza uses a cylinder head gasket. Every EJ-series flat-four fitted to this model year (including the EJ253 2.5‑litre SOHC in non‑turbo variants, the EJ205 WRX, and the EJ257 STI) relies on head gaskets between the aluminium heads and the block. This is documented in the 2005 Subaru Impreza Factory Service Manual (engine sections covering cylinder head removal, inspection and gasket installation) and reflected in the official Subaru parts catalogue, which lists specific head gaskets for each EJ engine. Subaru service literature also references cooling system conditioner usage for certain EJ25 applications, underscoring the gasket’s relevance.

The head gasket’s job is simple but critical: it seals combustion pressure, coolant, and oil passages where the cylinder head meets the block. In a boxer engine, those interfaces sit low and long on each side under the bonnet, so a healthy seal keeps compression strong, power consistent, and fluids exactly where they belong.

There’s no fixed replacement interval for a head gasket — it’s not a routine service item — but good cooling-system care goes a long way. Use the correct Subaru‑approved coolant mix, keep the radiator cap, thermostat, and hoses in good nick, and change coolant at the recommended intervals. If the model falls under Subaru’s guidance to use cooling system conditioner, follow the manufacturer’s instructions at service time.

• Watch for early signs: a sweet coolant smell, a light weep at the head/block seam, bubbles in the overflow, unexplained coolant loss, misfires on cold start, overheating under load, or milky contamination.
• If symptoms crop up, organise checks like a cooling system pressure test, a chemical test for combustion gases in the coolant, and compression/leak‑down testing.

When replacement is needed, proper procedure matters. On EJ engines, removing the engine from the car often makes access cleaner and helps ensure torque-angle sequences are followed precisely. Heads should be checked for flatness and resurfaced if out of spec