2012 Subaru Impreza Owner's Manual - Page 388

11-20 Maintenance and service Brake booster If the brake booster does not operate as described in the following, have it checked by your SUBARU dealer. 1. With the engine off, depress the brake pedal several times, applying the same pedal force each time. The distance the pedal travels should not vary. 2. With the brake pedal depressed, start the engine. The pedal should move slightly down to the floor. 3. With the brake pedal depressed, stop the engine and keep the pedal depressed for 30 seconds. The pedal height should not change. 4. Start the engine again and run for approximately one minute then turn it off. Depress the brake pedal several times to check the brake booster. The brake booster operates properly if the pedal stroke decreases with each depression. functions, and the brake assist system is operating properly. Brake assist is not a system that brings more braking ability to the vehicle beyond its breaking capability. Brake pedal Check the brake pedal free play and reserve distance according to the maintenance schedule in the "Warranty and Maintenance Booklet". & Checking the brake pedal free play 1) 0.02 - 0.08 in (0.5 - 2.0 mm) NOTE For vehicles equipped with the brake assist system, when you depress the brake pedal strongly or suddenly, you might feel that lighter depression of the brake pedal generates a greater braking force. However, even though these occur, they do not indicate any mal- Stop the engine and firmly depress the brake pedal several times. Lightly pull the brake pedal up with one finger to check the free play with a force of less than 2 lbf (10 N, 1 kgf). If the free play is not within proper specification, contact your SUBARU dealer.