I moved this thread from Brakes, Tires, and Suspension section to General Q&A. I am still looking for help with this. Any mechanics on this forum? I am having trouble trying to fix a low and soft brake pedal on my 2004 Silverado. I have already replaced the master cylinder, flushed and bled the brake lines at all four wheels. Still the pedal is low and soft. Does anyone know what it could be? There is no loss of brake fluid any where. The master cylinder reservoir is not losing fluid. My truck has disc brakes on all four wheels, and the pads are in good shape. I do not think there is anything wrong with the calipers because the truck does not pull to one side. To engage the parking brake, I have to push it down a lot more than usual. So, I am not sure if the problem is more likely the booster or the calipers. Can anyone help? BTW, sometimes the pedal will be high and firm, then sometimes it will go back to low and soft. If I pump the pedal they will get firmer. When at a stop, I can feel the pedal slowly sinking.