Subaru Forester: EJ25 Phase 2 head gasket failure

The EJ25 SOHC engine used in SH Foresters suffers chronic head gasket failure due to the original multi-layer steel (MLS) Phase 2 gasket design. The aluminium block and iron cylinder head have different thermal expansion coefficients, causing the gasket to fatigue and fail at the water jacket passages. External coolant seepage is the most common presentation, but internal combustion-gas intrusion into the coolant circuit accelerates overheating. This is the single most prevalent Subaru fault in the New Zealand market. Repair requires full head removal, resurfacing, OEM or Cometic aftermarket MLS replacement, and ARP head stud upgrade to prevent recurrence. Engine must not be operated once coolant loss begins.

• Coolant loss without visible external puddle
• White sweet-smelling exhaust smoke especially on cold start
• Bubbling in coolant overflow reservoir
• Overheating gauge climbing at idle or in traffic
• Milky residue under oil filler cap
• Coolant level drop over 2-4 weeks

1. 1

   Cold-start the engine and watch for white steam from exhaust.

2. 2

   Check coolant reservoir for bubbling under acceleration.

3. 3

   Remove oil filler cap and inspect for mayonnaise emulsion.

4. 4

   Request a combustion leak test (block tester / CO2 sniff test) on the coolant reservoir.

5. 5

   Check service history for recent coolant top-ups or head gasket work.

6. 6

   Inspect radiator for brown discolouration from combustion gases.

Parts involved: Head gasket.

$1,800 to $3,800 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 were ARP head studs fitted?”
• “Has the coolant ever been topped up between services?”
• “Has the engine ever overheated or has the temperature gauge ever risen above normal?”
• “Can I see the service history and any workshop invoices for head work?”

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.