Two problems related to brake master cylinder have been reported for the 2006 Toyota 4Runner. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2006 Toyota 4Runner based on all problems reported for the 2006 4Runner.
Brake pedal goes to floor. At stoplight pedal goes to floor and will not hold vehicle. Told it was a master cylinder. This is a $1500+ job. Dealer told me this never fails but out of warranty so their defect is my loss.
First issue: the brake pedal has a buzzing that occurs with every stop, it' is severe enough that it alters the brake pedal pressure. Second issue: when hitting a bump while stopping the brake pedal loses pressure. Would seem to be a concern for Toyota, they first said they haven't heard of a complaint, and then said it was normal.