Two problems related to brake fluid leak have been reported for the 2004 GMC Sierra 3500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 GMC Sierra 3500 based on all problems reported for the 2004 Sierra 3500.
Brakes failed due to a sudden brake line failure. There had been no prior fluid leaks. The rear metal brake line under the bed rusted at a clamp in front of the fuel tank. As I have looked further into this I have several friends that have had this problem and several shops said that they saw this often with these vehicles all failing in the same area.
On highway multi-lane, heavy traffic ahead, suddenly slowed and a lot of lane changing going on as some debris was ejected from truck onto roadway. Applied brakes, application had little effect. Stood on the brakes, butt out of the seat standing on the brakes, truck veered off to right severely while ant lock pulsed. Fortunately traffic got out of the way and escaped harm. Exited highway inspected vehicle. Upon exiting the truck found puddle of brake fluid on ground under driver¿s seat. Brake lines leaking. Sever rust throughout the brake system. Replacement of all brake lines required. This was very close to crash, only the rapid reflexes of the guy next to me averted an accident. Note, repair shop tells me that (and has shown me) all the brake lines must be replaced. As the lines enter a distribution box ( anti-lock anti-skid under the driver¿s seat) and the clamping devices all had significant rust to the point of failure.