Parts for your 2010 Subaru Legacy-Head gasket

2010 Subaru Legacy head gasket — what it does and how to look after it

Based on technical documentation, the 2010 Subaru Legacy absolutely uses head gaskets and the topic is relevant. The Subaru Factory Service Manual for 2010 Legacy/Outback (BR/BM) includes removal/installation and torque sequence procedures for the cylinder head gasket in the Engine section. Subaru’s genuine parts catalogues for MY2010 list head gaskets for the EJ253 2.5 petrol, EJ255 2.5 turbo, and EZ36D 3.6 petrol H6 engines. Being a boxer layout, each engine has two cylinder heads — and therefore two head gaskets.

The head gasket’s job is to seal the combustion chambers and keep coolant and oil in their own passages while the engine expands and contracts with heat. On a 2010 Legacy, good sealing means crisp performance, stable temps, and oil that stays clean. Poor sealing can show up as coolant loss, overheating, milky oil, exhaust bubbles in the coolant, or that tell-tale sweet smell under the bonnet.

Because the Subaru flat engine sits horizontally, any seepage tends to show along the block-to-head seam. Regular servicing keeps things sweet and can prevent early dramas:

• Stick with the correct Subaru long-life blue coolant and refresh at the intervals in the service schedule.
• Use a quality or genuine thermostat and radiator cap, cheapies can spike temps.
• Bleed air properly after cooling system work, air pockets can cook a gasket.
• Keep an eye out for dampness along the head seams and for unexplained coolant drops.

Head gaskets aren’t a routine replacement item — they’re done when there’s evidence of failure or during major engine work. If replacement is needed on an EJ25 Legacy, many owners take the opportunity to do the cam belt, water pump, idlers, and cam/crank seals in one go. On the EZ36D H6, space is tight and engine-out is common, so planning is key.

Best practice is to use the updated multi-layer steel gaskets, genuine or high-quality equivalent, replace head bolts, and have the heads checked and skimmed if required by a reputable machine shop. A workshop experienced with Subaru boxers will follow the correct torque/angle sequence and surface prep, which makes all the difference for long-term reliability.

Popular questions

Do all 2010 Subaru Legacy engines have head gaskets?
Yes. Every internal-combustion Legacy in 2010 uses head gaskets. With Subaru’s boxer layout, there are two cylinder heads — so two head gaskets — on both the 2.5 four-cylinder and the 3.6 six-cylinder.

What are the common signs of a failing head gasket on a 2010 Legacy?
Common clues include rising temps, coolant loss with no obvious leak, white exhaust steam on warm-up, bubbles in the overflow, oily residue in coolant, or milky discolouration under the oil filler cap. External dampness along the head-to-block seam is another one to watch on boxers.

How much does a head gasket job typically cost in Australia or New Zealand?
Ballpark, an EJ25 four-cylinder can run in the AUD/NZD 2,000–3,500 range depending on parts choice and how much “while you’re there” work is added (cam belt kit, water pump, seals). The EZ36D H6 is usually higher due to labour and access, often AUD/NZD 3,000–5,000+. Actual pricing varies by workshop and condition.