One of the most forgotten or misdiagnosed components is the seal between the master cylinder and the brake booster. If the seal or O-ring is leaking, it can cause a driveability issues with poor idle quality and lean DTC codes. Also, it can cause a hard brake pedal complaint from the driver. Andrew Markel covers how to inspect, replace and condition this critical seal. Sponsored by Auto Value and Bumper to Bumper.
Courtesy of Underhood Service.