WARNING: This page is about a different car, the 2003 Ford Thunderbird. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
Try not to roll the seal onto the housing when installing the seal or damage to the seal can occur.
Fig 1: Identifying Reverse Servo Piston Seal
Courtesy of FORD MOTOR CO.
Lubricate and install a new reverse servo piston seal.