Disc Brake Caliper: Reassembly

Lubricate piston seal with clean brake fluid, and install in cylinder bore groove. Lubricate cylinder with clean brake fluid. Coat piston and outside beads of dust boot with clean brake fluid.
Push piston through boot until boot is around bottom (closed end) of piston. See Fig 1 and Fig 2 . Position piston and boot directly over cylinder bore. Spread dust boot over piston as it is installed.
With bead seated in groove, carefully press straight down on piston until it bottoms in cylinder bore. DO NOT cock or jam piston in cylinder. If necessary, use a "C" clamp and a block of wood to bottom piston in cylinder.

Fig 1: Exploded View Of Single Piston Caliper (Bronco, E150 & F150; Others Similar)

Fig 2: Exploded View Of Dual Piston Caliper (E250/350 & F250/350; "F" Series Super Duty Similar)

Courtesy of FORD MOTOR CO.