Subaru Legacy: FB25 External Head Gasket Oil Seep (Driver Side)

The FB25 2.5L flat-four develops a well-documented external oil seep from the front of the driver-side (left) cylinder head gasket. Unlike the older EJ-series blown head gaskets, this is an external leak — oil tracks down the block and accumulates on the undertray. Subaru acknowledged this via TSB 02-157-14R. The root cause is the multi-layer steel gasket design combined with the aluminium block expansion cycle. Left unrepaired it worsens; it does not typically cause coolant contamination but can lead to a fire risk if oil contacts the exhaust.

• Oil residue or staining on the driver-side of the block near the head gasket join
• Oil accumulation on the undertray below the engine
• Burning oil smell from engine bay, especially after a run
• Slow but consistent drop in oil level between services
• Visible oil seepage when cold engine is inspected with a torch

1. 1

   Remove undertray and inspect the driver-side (left when facing engine) cylinder head-to-block joint for brown oily residue or fresh oil seepage.

2. 2

   Check for oil smell at idle and oil level drop between services.

Parts involved: Head gasket.

$700 to $2,000 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 resealed or replaced, and do you have dealer or workshop records?”
• “Has the undertray been removed recently — can I inspect it before purchase?”
• “What is the current oil consumption rate between services?”

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.