2025 Chevy, Buick, GMC Vehicles Plagued by Master Brake Cylinder Defect, GM Lawsuit Alleges

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A proposed class action lawsuit alleges that 2025 model year Chevrolet Traverse and Colorado, Buick Enclave and GMC Acadia and Canyon vehicles are equipped with defective master brake cylinder assemblies that can fail suddenly, causing a risk of collisions, serious injury and death.

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The 50-page class action lawsuit against General Motors says that many drivers have experienced partial or total loss of braking—where the brake pedal either “becomes stiff and hard to press, or sinks into the floor”—as a result of the alleged master brake cylinder defect. Drivers have reported trying “all manner of gimmicks,” including shutting off and restarting their vehicle and pumping the brake pedal, to try to get the brakes to work, the filing claims. 

According to the suit, master brake cylinder assemblies—which house the master brake cylinder, responsible for converting pressure applied to a car’s brake pedal into the hydraulic force that engages the brakes—typically do not require repair or replacement absent a defect. The lawsuit states that the brake master cylinder in the affected vehicle models is “defectively designed and/or manufactured,” as its internal seals and related components fail prematurely and allow brake fluid to bypass or leak, causing the loss of hydraulic pressure. 

“When the Master Cylinder Defect manifests, drivers experience dangerous conditions including brake pedals that feel unusually stiff or require excessive force to depress, brake pedals that sink to the floor without producing adequate braking power, substantial reduction or complete loss of braking capability, and activation of dashboard warning lights and messages such as ‘Brake,’ ABS warnings, and ‘Service Brake System.’”

Per the complaint, GM has failed to repair the problem within a reasonable period of time under its new vehicle limited warranty, despite having prior knowledge of the issue. The automaker has neither issued a widespread bulletin to dealers about the apparent master brake cylinder assembly flaw nor initiated a recall about the problem (or otherwise instructed dealers to perform repairs regardless of whether the defect has manifested), the lawsuit claims. 

“The Defect substantially impairs the Class Vehicles’ ability to provide safe and reliable transportation and renders the vehicles unmerchantable and worth less money at the time of sale or lease,” the case summarizes. 

Evidencing GM’s alleged prior knowledge of the brake master cylinder defect, the suit states that the automaker in December 2024 issued a service update in which it acknowledged problems in the brake master cylinder assemblies installed in 2024 Chevy Traverse and 2025 Buick Enclave vehicles. In that service update, dealers were instructed to inspect and, if necessary, replace the brake master cylinder “because internal seals or related components could fail,” causing the loss of hydraulic pressure and hampering brake performance, the filing says. 

As the case tells it, the service update “did not appear out of thin air,” as GM allegedly learned about the defect “months earlier” through its own testing, complaints from drivers and field reports. 

“Despite this prior knowledge, GM continued to install substantially similar master brake cylinder assemblies in the 2025 Class Vehicles and to market those vehicles as safe, reliable, and suitable for everyday use,” the class action lawsuit alleges. “GM concealed from consumers that these vehicles suffered from a defect that could suddenly impair braking performance and create a serious risk of collision.” 

The GM master brake cylinder lawsuit looks to cover all persons or entities who bought or leased a 2025 Chevrolet Traverse, 2025 GMC Acadia, 2025 Buick Enclave, 2025 Chevrolet Colorado or 2025 GMC Canyon vehicle in Pennsylvania or New York. 

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