The first thing to look at is the caliper mounting hardware, specifically the two slide bolts. If those have rust spots or the chrome plating has lifted, they will prevent the caliper from sliding freely. Those bolts must also be lubricated with high-temperature brake grease.
The best suspect is the brake fluid is being trapped somewhere in the hydraulic line and is unable to return to the reservoir. To identify that, stop on a slight incline when the problem is occurring, place a block about a foot downhill of one tire, shift to neutral, then open the hydraulic circuit in various places to narrow down the location of the restriction. An easy place to start is by loosening the steel lines at the master cylinder. Hope that doesn't let the brake release because the likely cause will have a very expensive solution.
The better suspect is a constricted rubber flex hose. If that is the cause, the brake will release when you open the bleeder screw on the new caliper. If that doesn't let it release, there has to be a mechanical problem with the caliper or its mounting hardware.
If the truck has four-wheel anti-lock brakes, the steel line leaving the hydraulic controller for the right front wheel can be loosened. If that lets the brake release, that eliminates the flex hose as a suspect, and points to the hydraulic controller. That controller is the least common suspect.
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Thursday, March 28th, 2019 AT 3:54 PM
