Parts for your 2018 Mitsubishi Asx-Brake booster

2018 Mitsubishi ASX brake booster — what it does and how to look after it

Referencing technical sources, the 2018 Mitsubishi ASX is fitted with a vacuum-type brake booster (also called a power brake unit). Mitsubishi Motors Service Manual for ASX/RVR 2017–2019 (Group 35A – Brakes) details booster function and checks, while the Mitsubishi ASA electronic parts catalogue for ASX/RVR (GA0W) lists brake booster assemblies (e.g., 4605A585/4605A586). Aftermarket fitment guides and workshop manuals covering 2010–2019 ASX models likewise specify a vacuum servo/booster. So the brake booster is absolutely relevant to the 2018 ASX.

On a 2018 Mitsubishi ASX, the brake booster is there to make every stop easy. It uses engine vacuum (petrol) or a vacuum pump’s supply (diesel) to multiply pedal effort, so the brakes bite firmly without the driver needing to stand on the pedal. Inside the booster, a diaphragm and control valve balance vacuum and atmospheric pressure as the pedal is pressed, giving strong, progressive assistance.

There’s no routine service interval for the booster itself, but it should get a regular once-over during scheduled servicing. Good workshops will:

• Inspect the vacuum hose and one-way check valve for cracks, loose clamps, and perishing.
• Listen for constant hissing at idle (a tell-tale vacuum leak).
• Do a quick function test: with the engine off, pump the pedal until it’s firm, start the engine, and confirm the pedal drops slightly as vacuum fills the booster.

Common symptoms that point to a tired or leaking booster include a hard brake pedal, extra stopping distance, uneven idle or stalling when the pedal’s held, and a whooshing sound near the firewall. If any of these pop up, it’s time to get it checked before the next WOF/roadworthy or big trip.

Replacement is straight-forward for a trained tech: the master cylinder is unbolted from the booster, the pedal clevis is disconnected inside the cabin, and the booster is swapped out. Best practice is to renew the vacuum hose and check valve if they’re brittle, fit a new gasket, set the pushrod/clevis length to spec for correct pedal height, and torque everything properly. If brake lines are opened, the system must be bled and the vehicle road-tested. Expect around 1.5–3.0 hours in typical workshop conditions. While the ASX can still be stopped with a failed booster, pedal effort skyrockets — not something anyone wants in city traffic or on a wet Kiwi back road — so prompt repair is the smart move.

Popular questions about the 2018 Mitsubishi ASX brake booster

What does the brake booster do on a 2018 Mitsubishi ASX?
It amplifies pedal force using engine or pump vacuum, so the driver gets strong, progressive braking with light pedal effort. Without it, the pedal feels rock-hard and stopping distances increase.

What are the signs the ASX brake booster is failing?
A hard pedal, hissing from the firewall, rough idle or stalling when holding the brake at a stop, and increased stopping distance are the big clues. Any of these should trigger a workshop inspection.

How is a brake booster replaced on a 2018 ASX and how long does it take?
The master cylinder is unbolted, the pedal clevis is disconnected, and the booster is swapped. The check valve and hose are often renewed. Setting the pushrod length and a final road test wrap it up. Most shops allow 1.5–3.0 hours.