One problem related to strut failure has been reported for the 1998 Toyota Sienna. The most recently reported issues are listed below.
Started to get clunking/rattling noises on highway that sounded like it was coming from front left driver's side. Reduced speed to 50 mph. About 5 miles from home brake light came on. Pulled over and found brake fluid leaking around front drivers side tire (about 9pm). Slowly drove to mechanic about 2 miles away and left car overnight. Returned next morning and examined brake fluid reservoir. Found very little fluid in reservoir - distributed across the entire bottom. Mechanic reported the front strut mounting failed (apparently a problem with these cars). After failing the strut punctured the bottom of the brake fluid reservoir (about 3/8" hole) at one of the corners (see photo) allowing the fluid to drain. Should I have lost almost all fluid with a 2 circuit braking system? does the reservoir have an internal baffle to prevent almost total lose of fluid? I am the original owner and have all maintenance receipts.