Brake Master Cylinder problems of the 2010 Volkswagen Jetta

My daughter has been driving her 2010 Jetta since June 2010 (purchased new). Until the end of 2016 she complained that her car started running unsmooth, jerky, the vsc warning light on/off randomly, unable to go faster than 60 mph on the freeway while the car was shaking violently and the engine revving aggressively. I verified her car driving condition myself. I was traveling above 70 mph on a 65-mph freeway zone. Suddenly the car started to shake violently as if all wheels were severely off-balanced. Ignoring my accelerator pedal, I could barely drive above 45 mph. I felt very unsafe in the middle of the road and prepared to be hit by another car at any moment. To achieve a desired quick brake pedal response on Volkswagen vehicles, the design engineers opted to increase the assembly interference between the brake master cylinder and the booster instead to reduce the brake pedal to the master cylinder piston travel ratio. They reduced the clearances from the master cylinder piston seals to the brake fluid supply/return ports so that the car brakes can be activated with shorter brake pedal stroke. As the results, under assembly dimensional tolerance stack-ups, some cars were built with the brake fluid supply/return ports partially or fully covered by the piston seals at the Volkswagen factories. When the thermally expanded brake fluid cannot flow back to reservoir through the fully covered supply/return ports easily, the fluid will expand brake caliber pistons pushing the brake pads against the rotors resulting brake dragging. When a moving car's engine cannot overcome with the brake dragging frictions, the car driver will lose his/her control to the vehicle speed. The o-ring swell due to aging made the Jetta worse. . Read more...