Parts for your 2013 Subaru Impreza-Brake booster

2013 Subaru Impreza Brake Booster — What it does and how to look after it

Technical sources including the Subaru factory service information (Brake “BR” section) and the genuine Subaru parts catalogue confirm that the 2013 Subaru Impreza (GP/GJ, FB20) is fitted with a vacuum brake booster mounted to the firewall, working with a tandem master cylinder. Subaru technical bulletins for FB‑series engines also reference the vacuum supply (via manifold vacuum and/or a cam-driven vacuum pump), further confirming the booster’s use on this model.

On this Impreza, the brake booster’s job is to use engine vacuum to multiply the driver’s pedal effort, so stopping feels light and confident without needing to stand on the pedal. It’s a simple, reliable bit of kit: a sealed housing with a diaphragm, a one‑way check valve, and a vacuum hose feeding it.

When it’s healthy, pedal feel is consistent and the car pulls up smartly. When it’s not, the driver may notice a hard brake pedal, increased stopping distance, a hissing sound at the pedal, or a rough idle when the brakes are applied (vacuum leak). Because the FB20 often relies on a cam-driven vacuum pump to keep vacuum steady, issues with the pump, its hose, or the booster’s check valve can all show up as poor brake assist.

As part of routine servicing, it’s smart to:

• Inspect the booster vacuum hose and check valve for cracks, oil soak, or loose fits every 10,000–15,000 km or annually.
• Listen for hissing near the pedal or firewall with the engine running.
• Perform a quick booster test: with engine off, pump the pedal until firm, hold pressure, then start the engine — the pedal should drop slightly as vacuum assist kicks in.

If replacement is needed, a quality OE or equivalent booster is recommended. Ensure the one‑way valve is oriented correctly, renew the master‑to‑booster seal, and torque fixings to spec. If brake pipes are opened, a fluid change and full system bleed are required. Many techs will slide the master cylinder forward to save cracking lines where possible, but on some cars lines must be disconnected — follow Subaru procedure. After fitment, confirm strong, even pedal feel and verify vacuum supply from the manifold or pump. Any oil leaks around the vacuum pump should be addressed promptly, as low vacuum can compromise assist.

Popular questions about 2013 Subaru Impreza brake boosters

How can someone quickly test the brake booster at home?
With the engine off, pump the brake pedal several times until it feels firm. Keep holding pressure and start the engine. A healthy booster will let the pedal sink slightly as vacuum assist arrives. No change usually points to a booster, hose, or check valve issue.

What are common symptoms of a failing brake booster or check valve?
A hard pedal, longer stopping distances, a hissing noise when pressing the brake, and a rough or high idle when braking are common signs. If the one‑way valve sticks or the hose splits, assist can be inconsistent, especially after repeated stops.

Does the 2013 Impreza use a vacuum pump for the booster?
Many FB20-equipped Imprezas use a cam-driven vacuum pump to stabilise vacuum supply for the booster, especially at low manifold vacuum. If the pump or its plumbing is compromised, brake assist can drop — so it’s worth checking pump condition and hose integrity during servicing.