Parts for your 2018 Subaru Impreza-Manifold gasket

2018 Subaru Impreza manifold gasket — what it does and when to replace it

Yes, the 2018 Subaru Impreza uses manifold gaskets. Both intake and exhaust manifold gaskets are specified for the FB-series engines fitted to this model. This is documented in the Subaru Service Manual for 2018MY Impreza (STIS) under the Engine/FB sections, which instructs replacing manifold gaskets whenever the manifolds are removed. Subaru’s official parts catalogue (FAST/Global EPC) also lists “Gasket – Intake Manifold” and “Gasket – Exhaust Manifold” for 2.0L FB20 vehicles of this year.

The manifold gasket is a hardworking seal that sits between the manifold and the cylinder head. On the intake side, it prevents unmetered air sneaking past the throttle and upsetting fuel trims, which keeps idle smooth and helps the ECU manage fuelling spot-on. On the exhaust side, it keeps hot gases inside the runners, protecting nearby components, keeping noise down, and ensuring the oxygen sensors get accurate readings for proper closed-loop control.

For a 2018 Impreza, manifold gaskets aren’t a periodic replacement item, but they are a must-replace whenever the intake or exhaust manifold is disturbed—think injector service, carbon clean, head work, or exhaust repairs. Best practice is to use new OEM or high-quality MLS/graphite gaskets, clean the mating faces until they’re spotless, and torque the fasteners in the factory sequence to spec from the Subaru manual. Avoid sealants unless the procedure explicitly calls for them. On the exhaust side, a squirt of penetrating oil on studs, new nuts where required, and a quick check for warped flanges or cracked heat shields will save headaches later.

Common signs of a tired or leaking manifold gasket include:

• Hissing or whistling at idle (intake leak), or a ticking/putt-putt on cold start (exhaust leak)
• Rough idle, hesitation, or higher-than-normal fuel trims and a lean code (e.g., P0171)
• Exhaust smell under the bonnet or in the cabin, soot marks near the flange, or louder exhaust note
• Drop in fuel economy or sluggish performance

There’s no strict kilometre interval, but many workshops renew intake gaskets whenever the manifold comes off, and inspect the exhaust joints after 100–150,000 km or if any of the above symptoms show up. If fumes are noticeable in the cabin, park it up and sort it promptly—exhaust leaks aren’t just annoying, they can be unsafe. Keep it OEM-quality, keep it clean, and torque it right, and the Impreza will stay sealed and happy.

FAQs

Does the 2018 Subaru Impreza have manifold gaskets?
Yes. The Subaru Service Manual for the 2018MY Impreza (FB engine) details intake and exhaust manifold removal with replacement of their gaskets, and the Subaru parts catalogue lists both gasket types for this model.

What are the signs of a failing manifold gasket on a 2018 Impreza?
Listen for a hiss at idle (intake) or a ticking on cold start (exhaust). Watch for lean codes like P0171, rough idle, poor economy, exhaust odour near the engine bay, or soot at the flange. Any of these warrant inspection.

Should sealant be used when installing a manifold gasket?
Generally no. The factory procedure calls for clean, dry mating surfaces and new gaskets, torqued in sequence to spec. Only use sealant if the Subaru manual specifically instructs it for a particular joint.