Cruise Control Problems of Chevrolet Sonic

I was driving on the highway at between 55 and 65 mph. The side I was on had a long, steady incline upward. I had set my cruise control to about 63 mph. As I was going uphill the cruise control was supplying fuel to get to and maintain my speed at 63 mph. I was approaching another car in my lane and decided rather than pass, I would slow down. They were going quite a bit slower than me so came up upon them quickly. I pressed the brake to slow down but the brake was hard as a rock. It would not budge so it did not disconnect the cruise control and my car kept accelerating. I panicked and tried to use both feet on the brake. It still would not budge. I was within 2 car lengths of the car in front of me when finally the car reached the speed I had set the cruise control for and the brakes finally depressed. In hindsight, I had options I. E. Putting the car in neutral, turning key off, turning to avoid a collision, shutting off cruise control, but this car was new to me, and in that moment I fully expected the brakes to work. Once I was in control, I tried to recreate the problem with no one around, knowing my options now. It happened repeatedly. A service tech also had it happen to them. First attempt at repair did not fix it. Second attempt did. It was a bad check valve. Apparently the check valve let air out of a booster, so I lost my brakes? the check valve also let fluid fill the booster. The master cylinder and vacuum were replaced as well. Looking back, there were signs, but no obvious ones. A random hi-pitched noise (air squeaking out the check valve). Loss of brake fluid. Dealer had to fill it when I bought it and I added some at 6 months. This was a dangerous and scary experience. I question the design to dis-engage cruise control and the quality of the check valves themselves.

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