Consequently, the valve O-ring seal may fracture. Steering efforts may be slightly increased while braking or parking. Under certain driving conditions, a fractured seal may require a slight increase in the applied brake pedal effort to achieve the same vehicle deceleration rate as prior to the seat fracture.
Certain sport utility vehicles, pickup trucks, and passenger vans fail to comply with the requirements of Federal Motor Vehicle Safety Standard no. 135, "passenger car brake systems." Some of these vehicles were produced with an out-of-specification brake hydro-boost housing relief valve bore.
Dealers are to replace the hydro-boost relief valve. The recall began on June 18, 2004. Owners should contact Cadillac at 1-866-982-2339; Chevrolet at 1-800-630-2438; GMC at 1-866-996-9463; or Hummer at 1-866-486-6376.