EJ25 SOHC Head Gasket Failure

Subaru's most famous defect — external coolant/oil leaks from the head gasket on 1999-2009 2.5L.

Last updated: 2026-05-10

Repair cost

$1,800–$3,200

Both heads; add timing belt + water pump while you're in there

DIY difficulty

4 / 5

Severity

Major

Costly to ignore — plan a fix within weeks

Affected

1999-2009

EJ251, EJ253, EJ252

What goes wrong

The multi-layer steel head gasket fails between the cylinder and the oil/coolant gallery, causing external leaks. Unlike the EJ22T, it rarely fails between the cylinder and water jacket — so combustion gas in coolant is uncommon.

Symptoms to watch for

Sweet smell from engine bay
Coolant or oil residue on the side of the block, just below the head
Slow coolant loss with no visible puddle
Overheating in stop-and-go traffic

Root cause

OEM gasket composition + thermal cycling. Updated 6-layer gasket (P/N 11044AA770) resolves it.

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Buy time with these

• Subaru cooling-system conditioner (P/N SOA868V9270) — buys time, not a fix

Permanent fix

Replace both head gaskets with updated 6-layer P/N 11044AA770
Resurface heads
New head bolts (TTY)

FAQ

What causes ej25 sohc head gasket failure?

OEM gasket composition + thermal cycling. Updated 6-layer gasket (P/N 11044AA770) resolves it.

How much does it cost to fix?

National average $1,800–$3,200. Both heads; add timing belt + water pump while you're in there

Is this a DIY repair?

Difficulty 4/5. Replace both head gaskets with updated 6-layer P/N 11044AA770

What are the symptoms?

Sweet smell from engine bay; Coolant or oil residue on the side of the block, just below the head; Slow coolant loss with no visible puddle; Overheating in stop-and-go traffic

Sources

• Subaru TSB 02-129-09R