One problem related to brake master cylinder has been reported for the 1997 Chevrolet C2500. The most recently reported issues are listed below.
Brake pedal sank completely to floor and remained at floor for approximately 0. 5 to 1 second before brake system began operation and pedal began to return to normal feel. Condition has happened two times on this vehicle. During most recent incident, I had to react quickly to vehicles stopping in front of me, engine load went from maintaining steady 55 mph to deceleration. Brake booster on this vehicle is hydraulic, driven by the power steering pump. The delay in brake operation is significant enough, in my opinion, that the vehicle could cause an accident. Have not had system serviced because I cannot duplicate the problem.