Parts for your 2017 Subaru Forester-Head gasket

2017 Subaru Forester head gasket: purpose, care and when to replace

A head gasket is absolutely present on every 2017 Subaru Forester engine. Technical documentation confirms it: the Subaru Factory Service Manual for the 2017MY Forester (engine sections covering FB25 2.5‑litre, FA20F 2.0‑litre turbo, and EE20 diesel) specifies a cylinder head gasket, and Subaru’s global FAST parts catalogue lists the OEM head‑gasket assemblies for these engines. Being a horizontally opposed (boxer) design, the Forester runs two cylinder heads, so it has two head gaskets. It’s a genuine, critical service component on this model.

The head gasket’s job is to seal the mating surface between the aluminium cylinder head and the engine block. It keeps combustion pressure inside the cylinders while also sealing oil and coolant passages so the fluids don’t mix or leak externally. On 2017 Forester engines, the gasket is a robust multi‑layer steel (MLS) design used with torque‑to‑yield head bolts. This setup handles heat cycles and pressure well when the cooling system is healthy. If a gasket loses clamp or the engine overheats, compression can drop, coolant can enter a cylinder, or oil and coolant can contaminate each other—none of which the Forester appreciates on Aussie or Kiwi roads.

The head gasket isn’t a routine service item and doesn’t have a scheduled replacement interval. Sensible care helps it last the life of the engine: keep the cooling system in top nick, run the correct Subaru blue long‑life coolant per the logbook, don’t mix coolant types, fix leaks early, and ensure radiator fans, the cap and thermostat are working properly. A workshop inspection around the head‑to‑block seam for weeping is smart during regular servicing. Typical warning signs include:

• Unexplained coolant loss, overheating, or pressurised hoses when cold
• White exhaust vapour after warm‑up, sweet coolant smell, or misfire on cold start
• Milky residue under the oil filler cap or in the overflow bottle

Replacement is required only if the gasket fails or when the head is removed for other major work. Proper repair on a 2017 Forester means following the Subaru FSM torque‑angle sequence, using new head bolts, checking head and block flatness, pressure‑testing the head, and renewing related gaskets, coolant and engine oil. Quality OEM‑spec MLS gaskets are strongly recommended. A reputable workshop familiar with Subaru boxer engines will also bleed the cooling system correctly and road‑test under load to verify a stable temperature and no residual combustion gases in the coolant.

Popular questions

Do all 2017 Subaru Foresters use a head gasket?
Yes. The Subaru Factory Service Manual and the Subaru FAST parts catalogue both specify head gaskets for the 2017 Forester’s FB25, FA20F and EE20 engines. The boxer layout means two cylinder heads and therefore two head gaskets.

What are the signs of a failing head gasket on a 2017 Forester?
Common clues include ongoing coolant loss, overheating, white vapour from the exhaust after warm‑up, sweet coolant odour, rough cold starts or misfire, and cross‑contamination of oil and coolant. A cooling‑system pressure test and chemical block test help confirm the diagnosis.

When should a 2017 Forester head gasket be replaced?
There’s no kilometre‑based interval. It’s replaced only when failed or when the head is off for other repairs. Preventive focus is on cooling‑system maintenance—correct coolant, leak repairs and avoiding overheating—to maximise gasket life.