The brake line bolt will be 14mm or 9/16" and be sure to obtain and use new copper washers at the connection. The bleeder screws are usually 10mm or 3/8" which is usually too loose. I recommend breaking them all loose with a 6-point socket then close them before you start then using a wrench will be easier. A seized caliper piston can cause this concern when dual piston calipers are used. With these trucks however you need to be sure that the caliper slide pins are not seizing up as well. I have also seem many times whenre the brake pads and rotors were badly rusted and coming apart which can cause the spongy feel.