Subaru Forester: EJ20 Head Gasket Failure at Coolant Passages

The EJ20 boxer engine (both naturally aspirated and turbocharged variants) suffers from a well-documented failure of the multilayer steel head gasket at the external coolant passages on the cylinder head face. The aluminium block and iron-lined cylinder head expand at different rates under thermal cycling, causing the gasket to fail at the water jacket ports. This allows coolant to weep externally down the block rather than entering the combustion chamber in early stages, making it easy to miss until overheating damage occurs. Later-stage failure allows coolant and combustion gases to cross-contaminate. The 2.0-litre EJ20 in SG (2002-2008) and SH (2008-2013) Foresters is particularly affected. Subaru acknowledged the issue with an extended warranty campaign in several markets.

• Visible coolant weeping or residue staining on the side of the block between the head and block mating face, often with white crusty deposits
• Coolant level dropping without visible puddle underneath the car, often requiring frequent top-ups
• Temperature gauge climbing above normal or intermittent overheating, particularly under load or in slow traffic
• Sweet smell from the engine bay after driving, sometimes accompanied by light steam from around the exhaust manifold area

1. 1

   Check for combustion gases in the coolant using a block tester (combustion leak test kit).

2. 2

   Inspect coolant for brown discolouration or oily film.

3. 3

   Compare coolant level between cold starts over several days.

4. 4

   If a workshop inspection is possible: Pressure-test the cooling system cold and watch for pressure drop.

5. 5

   Remove the undertray and inspect both sides of the block at the head-to-block join for brown or white mineral staining.

Parts involved: Head gasket.

$2,200 to $4,800 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 if so can you show the workshop invoice with the replacement gasket part number?”
• “Has the car ever overheated or required coolant top-ups between services?”
• “Is the coolant level currently at the correct mark, and what colour is the coolant in the reservoir?”

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.