Parts for your 1999 Subaru Forester-Head gasket

1999 Subaru Forester Head Gasket — What It Does and When to Sort It

Yes, the 1999 Subaru Forester absolutely uses a head gasket. That’s straight from technical sources: the 1999 Forester SF Series Service Manual (Engine: Cylinder Head section) specifies the gasket and torque sequence, Subaru parts catalogues list cylinder head gaskets for both EJ20 and EJ25 engines fitted to this model year, and Subaru Technical Service Bulletin 09-36-03 addresses external coolant seepage at the cylinder head gasket on late‑90s/early‑2000s 2.5‑litre engines, including Forester. So the head gasket is relevant, used, and critical on a ’99 Forester.

On this boxer engine, there are two head gaskets—one per bank. Their job is to seal the combustion chambers and keep oil and coolant in their own circuits under pressure and heat. A healthy head gasket maintains compression for proper power and efficiency, while preventing coolant from sneaking into oil (or vice versa) and stopping combustion gases from bubbling into the cooling system. Because the engine lies flat, good sealing on both sides matters heaps for smooth running and long life.

Owners in Australia and New Zealand often know the EJ25 from this era can develop external coolant leaks as the gasket ages. Subaru even released a Genuine Cooling System Conditioner as a mitigation. Smart servicing for a 1999 Forester means fresh Subaru‑spec coolant at the proper mix, the conditioner where applicable, and regular checks under the bonnet. Keep an eye out for these signs:

• Sweet smell, dampness, or crusty residue around the head‑to‑block join
• Unexplained coolant loss or bubbles in the overflow bottle
• Overheating on climbs or in traffic
• Milky residue on the oil cap or dipstick
• Rough cold starts or exhaust steam after warm‑up

When replacement time comes, a workshop familiar with Subaru flat‑fours is worth its weight. Quality multi‑layer steel (MLS) gaskets, precise head‑bolt torqueing in sequence, and clean, flat mating surfaces are non‑negotiable. Many shops also recommend doing both sides, plus “while you’re there” items to save future labour:

• Timing belt, idlers, and tensioner (aligns nicely with typical kilometre intervals)
• Water pump, thermostat, and radiator cap
• Heater and radiator hoses, and fresh Subaru coolant with the correct conditioner where specified
• Check head bolts for stretch, replace if out of spec

Pressure testing, a chemical block test, and a cooling‑system check are quick ways to confirm issues early. Avoid overheating at all costs—heat is the enemy of head gaskets and alloy heads. Done right, a fresh set and a healthy cooling system will keep a ’99 Forester humming for many more kilometres.

Popular questions about 1999 Subaru Forester head gaskets

What are the tell‑tale signs the head gasket is failing on a 1999 Forester?
Typical clues include coolant seepage at the head‑to‑block join, bubbles in the overflow bottle after a drive, unexplained coolant loss, and a temperature gauge that creeps up under load. You might also spot white steam from the exhaust once warm, or find milky residue on the oil cap.

If you notice any of these, avoid long trips or heavy loads and book a pressure test and block test. Catching it early usually means a simpler repair and less chance of warped heads.

Should both head gaskets be replaced at once on the boxer engine?
Most Subaru‑savvy workshops recommend doing both sides. Labour overlaps heavily, and replacing just one bank can lead to doing the other soon after, doubling downtime and cost. Doing both, machining as needed, and refreshing the cooling system gives the best long‑term reliability.

It’s also an ideal time to tackle the timing belt, idlers, and water pump, because access is open and you’ll save on future labour.

How can they make a replacement head gasket last longer?
Use quality MLS gaskets, follow the correct torque sequence, and keep the cooling system in top nick with Subaru‑approved coolant (and the genuine conditioner where specified). Renew the thermostat, cap, and tired hoses so pressure and temperature stay stable.

Stick to coolant change intervals, bleed air properly, and never ignore early overheating. A cool, clean system is the best insurance for gasket longevity.