One problem related to brake foundation components has been reported for the 2005 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2005 Toyota Sienna based on all problems reported for the 2005 Sienna.
I have a 2005 Toyota Sienna van that has intermittent brake failure. It normally occurs when the car is cold. I have run several red lights with the brake pedal pressed completely to the floor and my wife has driven through two yards. The brakes function normally on the first several applications but on the third or fourth application they will occasionally fail. My dealership has replaced the master cylinder and done "diagnostics" at least 8 different times but consistently find nothing. They did tell me that other vehicles were experiencing the same sorts of problem and it had something to do with a new valve timing on the 2005 model and the vacuum was insufficient until the car was warm and that I should idle for 5 minutes before driving. This seems to work more consistently but I still have episodes of poor braking. We have been attempting to have this resolved for almost 18 months.