Subaru Impreza: EJ20 Head Gasket Failure at Coolant Passages

The Phase I and Phase II EJ20 naturally-aspirated and lightly-turbocharged engines used in GD Imprezas are prone to external and internal head gasket failure. The multi-layer steel gasket fails at the coolant passage between cylinders 2 and 3 on both cylinder banks, causing coolant to leak externally down the block or, in more severe cases, enter the combustion chamber. The aluminium head expanding and contracting against the iron-lined block accelerates gasket fatigue, particularly when the cooling system is not maintained and the coolant becomes acidic. Subaru issued updated composite gaskets (SOA 10105AA560) as a remedial measure but the design remained prone to failure through the generation.

• Unexplained coolant loss with no visible puddle under the vehicle
• White steam or sweet-smelling exhaust smoke particularly on warm-up
• Overheating gauge rising on long uphill runs or in traffic
• Brown staining or white crusty deposits on the engine block below the cylinder head joint

1. 1

   Inspect for white crystalline deposits on the block face below the exhaust manifold.

2. 2

   Check coolant for brown discolouration or oil contamination.

3. 3

   Check oil cap underside for a white mayonnaise residue indicating combustion gas ingress.

4. 4

   If a workshop inspection is possible: Pressure-test the cooling system and observe for coolant loss without a visible external leak.

Parts involved: Head gasket.

$1,400 to $3,200 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “Has the head gasket ever been replaced, and do you have the workshop invoice?”
• “When was the coolant last flushed, and what condition is it in?”
• “Has the car ever overheated or shown a high temperature gauge reading?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.