I have had this problem for as long as I have had the truck, but never really worried about it. When I push on the Brake Pedal it comes all of the way back up to the top, but when you look at the brake lights they stay on for about 5-10 seconds after I let my foot off the pedal. Also the the pedal feels a little "mushy". What could this be? Master Cylinder? Rear Brakes?