Two problems related to brake master cylinder have been reported for the 2008 Toyota Sienna. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2008 Toyota Sienna based on all problems reported for the 2008 Sienna.
Brake pedal would go to floor and experienced no braking. Dealer stated "brake components seized and internal failure in master cylinder".
I was driving 35 mph on at least 4 seperate occassions when my I applied my brakes, they completely failed. I took it back to Toyota and they kept it for 10 days, flushed the brake lines 4 times, replaced the master cylinder, charged me $600 and made me sign a form saying the van was unsafe to drive because they have no idea what was wrong with it.