Subaru's most famous defect — external coolant/oil leaks from the head gasket on 1999-2009 2.5L.
Reviewed by SubaruReview Editorial Team · Last reviewed 2026-05-10 · Editorial standards
How this problem ranks against the other documented Outback failures — cost, severity, and DIY difficulty at a glance.
| Problem | Years | Severity | Repair cost | DIY |
|---|---|---|---|---|
| EJ25 SOHC Head Gasket Failure (this page) | 1999-2009 | Major | $1,800–$3,200 | 4/5 |
| Catalytic Converter Failure (P0420) | 2010-2019 | Major | $1,500–$2,500 | 3/5 |
| Excessive Oil Consumption | 2011-2015 | Major | $3,500–$5,500 | 1/5 |
| Outback PCV Valve Oil Leak | 2010-2019 | Minor | $30–$250 | 1/5 |
This is one of several documented Outback problems we track, and it fits inside the broader Engine Guides guide. If you're weighing repair against replacement, cross-check the Subaru repair-cost database and any open NHTSA recalls on your VIN before booking a shop.
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.
OEM gasket composition + thermal cycling. Updated 6-layer gasket (P/N 11044AA770) resolves it.
OEM gasket composition + thermal cycling. Updated 6-layer gasket (P/N 11044AA770) resolves it.
National average $1,800–$3,200. Both heads; add timing belt + water pump while you're in there
Difficulty 4/5. Replace both head gaskets with updated 6-layer P/N 11044AA770
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
Owners typically pay $1,800–$3,200 at an independent Subaru shop, parts and labor included. Our Subaru Head Gasket Replacement Cost guide breaks the job down by parts, labor hours, and where the money actually goes.
The same generation also sees Catalytic Converter Failure (P0420) and Excessive Oil Consumption. Both are documented with symptoms, cost, and a permanent-fix walkthrough — see the full list in the Outback hub.
We rate it 4/5 on our DIY scale. Most owners come out ahead with an independent Subaru shop; read labor-hour benchmarks in the repair-costs hub before you commit tools and a weekend.
It's part of our Engine Guides cluster, which collects every article covering the same system as this failure.
Same EJ-family boxer — the failure mode carries across every chassis this engine shipped in.
Same EJ-family boxer — the failure mode carries across every chassis this engine shipped in.
EJ, FA, FB, and EZ boxer deep-dives — the engine background this failure sits inside.
Dig into the Problems Database to plan your next maintenance sprint, or browse every model hub for buyer's guides, generation breakdowns, and known-issue lists.