One problem related to brake master cylinder has been reported for the 2004 Toyota 4Runner. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 Toyota 4Runner based on all problems reported for the 2004 4Runner.
While driving at approximately 30 mph on a city street, with children in vehicle, breaks failed and loud cabin alarm sound and abs, vsc and trac dash lights came on. I had to pull into a grassy swale, apply emergency break and down shift in order to stop and avoid crashing into traffic. Had vehicle towed to dealership. Abs pump break master cylinder was replaced at a cost of $3,300. I have read many posts in blogs from Toyota owners with similar issue, and some that caused accidents. I had just come off the highway, so this could have caused a serious accident just minutes earlier. Merits an investigation.