Parts for your 2015 Mitsubishi Lancer-Brake booster

2015 Mitsubishi Lancer brake booster — what it does, why it matters, and how to look after it

Yes, the 2015 Mitsubishi Lancer is fitted with a vacuum-assisted brake booster (also called a power brake unit) across its petrol variants, including CJ/CF-series 2.0L and 2.4L models, and turbocharged variants that use a vacuum pump. This is confirmed by technical references including: Mitsubishi Lancer CJ/CF Workshop/Service Manual (Group 35A – Service Brakes: Power Brake Unit/Vacuum Brake Booster), Mitsubishi Genuine Parts Catalogue (Brake – Power Brake Unit), and the Haynes Repair Manual for Mitsubishi Lancer 2007–2017 (Brakes chapter – Power brake booster inspection and replacement). These sources describe the vacuum-type booster, check valve, diagnostic tests, and replacement procedures for 2015 model-year vehicles.

The brake booster on a 2015 Lancer is there to make everyday braking feel natural and confidence-inspiring. It uses engine vacuum to multiply the force from a driver’s foot, so the car pulls up smartly without needing to stomp on the pedal. On naturally aspirated Lancers the booster draws vacuum from the intake manifold, on turbo variants a dedicated vacuum pump maintains assistance even when manifold vacuum is low. Either way, the result is a consistent, easy pedal with solid stopping power.

There isn’t much to “service” inside a booster, but there’s plenty the technician can check during regular brake work. The vacuum hose and one-way check valve should be inspected for cracks, loose clamps or perishing, the grommet at the booster housing should be snug, and the area between the master cylinder and booster should be dry. Any brake fluid seeping into the booster can damage the diaphragm and quickly snowball into a hard pedal and longer stopping distances.

Tell-tale signs the booster or its vacuum supply needs attention include:

• A noticeably hard brake pedal and increased pedal effort
• A hissing noise at the firewall or a change in engine idle when pressing the pedal
• Longer stopping distances or the pedal sitting higher and feeling “wooden”

If replacement is on the cards, a quality new or reman unit is the go. The job typically involves disconnecting the master cylinder from the booster (often without cracking the brake lines), separating the pushrod at the pedal, and transferring or adjusting the pushrod length to factory spec as per the workshop manual. If the lines are opened, the system should be bled. Refit the brake light switch correctly, torque all fasteners to spec, and finish with a road test to confirm pedal feel and brake balance. As part of normal servicing, it’s smart to have the booster hose and check valve looked over annually or at every brake pad/rotor service.

Popular questions about the 2015 Mitsubishi Lancer brake booster

• Does the 2015 Lancer have a brake booster?
  Yes. All 2015 petrol Lancer models use a vacuum-assisted brake booster (power brake unit). Turbocharged variants use a vacuum pump to ensure steady assistance under boost.
• What are the signs my Lancer’s brake booster is failing?
  Common clues include a hard, high pedal, a hissing sound from the firewall, a change in idle when braking, and increased stopping distances. Any fluid around the master cylinder/booster joint is also a red flag.
• Is it safe to drive with a bad brake booster?
  It’s not recommended. The car will still have brakes, but pedal effort shoots up and stopping distance can blow out, especially in an emergency. Get it checked and repaired before regular driving.