The goal is to get it to act up, then stop on a slight incline, shift to neutral, place a block about a foot downhill of one tire, then open the hydraulic system at various places to see where the brake fluid is being trapped. Most commonly that is inside one of the front rubber flex hoses. If that is the cause, the brake will only release when the bleeder screw on that caliper is opened.
You can also loosen the two soft metal line nuts at the master cylinder. If that lets the brakes release, that is the worst possible outcome because it points to the brake fluid is contaminated with a petroleum product. The only proper fix for that is to remove every part that has a rubber part in it that contacts the brake fluid, flush and dry the steel lines, then install all new parts with rubber in them. That repair can exceed the value of the truck, especially if it has anti-lock brakes. The hydraulic controller has rubber seals and o-rings so it must also be replaced.
Tuesday, April 9th, 2019 AT 6:25 PM