Two problems related to brake fluid leak have been reported for the 1999 GMC Sierra 2500. The most recently reported issues are listed below.
While attempting to slow the vehicle to exit the highway, the brake pedal went to the floor and there was limited braking. The vehicle had to be slowed by down shifting. After the vehicle was off of the highway, the brake warning light illuminated. The vehicle was taken to the dealership where mechanics found that one of the steel brake lines had rusted and ruptured causing the brake fluid to leak and the reduction in braking ability. All of the steel brake lines are severely rusted and need to be replaced due to concerns of additional failures.
Brakes failed as brake line corrosion allowed fluid leak. This was first of multiple line failures in the last three years. Three different factory lines failed then one transmission line. This truck is not used during winter and was under coated multiple times. No other part on this truck is corroded nearly as much as every steel line on it, including the gas lines( also replaced just last year) truck runs and drives excellent except for this corrosion problem.