Anyone else experienced this? 2016 sierra crew cab 5.3, 320km on it. Had drove it from Calgary to Kelowna as I was in kelowna going down hill i could not stop (was also going under the speed limit thank God it probably saved my life). I had a truck full of pvc fittings maybe an extra 1000-1500 lbs as I was going slowly down hill the brakes just would not work all I could hear was air coming out when I pumped them and I crashed the truck. Anyone have an idea what could’ve happened?