Parts for your 2020 Subaru Impreza-Brake booster

2020 Subaru Impreza Brake Booster — What It Does and How to Look After It

Yes, the 2020 Subaru Impreza is fitted with a vacuum brake booster. Technical sources including the Subaru Service Manual (STIS) for the 2017–2021 Impreza (GK/GT) list a “Vacuum Booster” in the Brake > Power Assist section, and Subaru’s genuine parts catalogue shows a “Booster Assy – Brake” for the 2020 model with the FB20 engine. The owner’s manual also describes pedal feel checks that rely on normal booster operation. So, the brake booster is absolutely relevant on this model.

The brake booster’s job is to multiply the driver’s pedal effort using engine manifold vacuum, so stopping feels confident without standing on the pedal. Mounted on the firewall under the bonnet and coupled to the master cylinder, it uses a one-way check valve and diaphragm to create a pressure difference that assists braking. On cars with EyeSight, the assisted system works hand-in-glove with ABS, EBD and stability control to keep braking smooth and predictable.

Day to day, the booster is largely maintenance-free, but it’s smart to inspect it during regular servicing. A workshop should check the vacuum hose and check valve for splits, perishing or loose clamps, confirm there’s no hissing at idle, and perform a simple function test: with the engine off, pump the pedal a few times, hold pressure, then start the engine — the pedal should sink slightly as assist kicks in. A brake fluid flush every two years, as per Subaru’s schedule, helps protect the master cylinder and prevents contamination that can harm seals over time.

• Hard pedal and longer stopping distances
• Hissing noise near the pedal or from the booster area
• Engine stumbling at idle from a vacuum leak
• Pedal not dropping when the engine starts after being pumped

If replacement is needed, a trained tech will disconnect the vacuum hose, unbolt the master cylinder from the booster, release the pedal clevis under the dash, and remove the booster’s mounting nuts. Care is taken to avoid spilling brake fluid into the booster and to set the pushrod length to spec so pedal height and feel are spot on. Most 2020 Imprezas use manifold vacuum, even with stop–start there’s stored vacuum in the booster, so no separate electric pump is typically fitted. If any doubt exists about assist performance, organise a proper inspection — brakes aren’t the place to gamble.

Popular questions about 2020 Subaru Impreza brake boosters

How long does a brake booster usually last on a 2020 Impreza?

There’s no set replacement interval. Many last well over 10 years and hundreds of thousands of kilometres. Replacement is driven by symptoms like a hard pedal, vacuum leaks, or internal diaphragm failure. Regular checks of the vacuum hose and timely brake fluid servicing help extend its life.

Does the 2020 Impreza have an electric vacuum pump for the brakes?

On most trims it doesn’t. The FB20 engine supplies manifold vacuum, and the booster’s check valve stores enough assist for a couple of pedal applications during stop–start events. If a diagnostic shows low vacuum reserve, a technician will check the hose, check valve and engine vacuum before suspecting any auxiliary hardware.

What’s the quick at-home test for a failing brake booster?

With the engine off, pump the brake pedal several times, hold it, then start the engine. If the booster is healthy, the pedal will drop slightly as vacuum assist returns. No drop, persistent hissing, or a very hard pedal suggests it’s time for a workshop check.