Three problems related to brake master cylinder have been reported for the 2005 GMC Sierra. The most recently reported issues are listed below.
On 11-30-2015 I lost the brake system while driving on a city street. Upon inspection I found a ruptured brake line from the primary side of the master cylinder. The brake line had failed due to corrosion. Inspecting other brake lines, I found others that had corrosion where plastic clips were used to locate lines. I have owned this truck since new and have cared for it meticulously. The truck has 66,00 miles on it. I have never owned any vehicle that had it brake lines rust through like this. A major catastrophe to me and my family was averted by pulling over at the first sign of failure. Gm should be held liable for every vehicle it manufactured with poor quality materials that can cause failure to the single most important part of an automobile, the brakes. As you can see from the attached photos, this truck is not rusted anywhere else.
The problem is a totally rusted-out set of steel brake lines throughout the GMC truck. The burst brake line is in the engine compartment. It is the line that runs from the antilock brake distribution point (attached to the frame beneath the driver seat). It runs along the frame, above the frame rail and past the steering box, and then makes a right turn beneath the radiator to the passenger side of the truck, where it exits into the wheel well and connects to the flexible brake hose on the passenger side. The steel line burst in the area adjacent to the steering box, so that it sprays brake fluid all over the steering box whenever the brake pedal is depressed. This quickly emptied the reservoir on the master cylinder leaving almost no brakes at all. There is very minimal braking available with the pedal fully depressed the floor. I initially examined the system to see if there is any chance of a do-it-yourself repair but quickly abandoned that idea. All of the brake lines are badly corroded and covered with scale, so there is no chance of cutting out the bad segment, double flaring the ends, and splicing-in a short segment to replace the rusted-out portion of the brake line. All of the brake lines throughout the truck are badly rusted and likely will fail again if left in place (according to the GMC service manager). The brake line that failed burst in a part of the engine compartment that would seem to not even be exposed to road salt, since it is inside the engine compartment and relatively shielded from salt spray and road grime by the body, wheel well and frame rail. The dealer service manager in murphy, nc estimates that it will take one of his mechanics almost a full day to remove all of the bad brake lines and fabricate replacements (these lines are not available in prefabricated form from GMC.
Tl- the contact owns a 2005 GMC Sierra. The contact stated that while driving at various speeds, she applied the brakes and the vehicle slid a small distance. The contact then pumped the brakes and the brakes functioned normally. The vehicle was taken to an independent mechanic for diagnosis and the contact was informed that the flex hoses lines from the master cylinder and the abs pump to the rear calipers would all need to be replaced. The vehicle was not repaired. The failure mileage was unknown and the current mileage was 70,000. Kmj.