Vehicle models equipped with an Anti-lock brake system (ABS) will have either the MK25 or MK25E factory systems installed. The MK25, an earlier ABS system, can be identified by a pressure sensor mounted to the bottom of the master cylinder, while the MK25E, a later system, does not have this sensor. To check the operation, depress the brake pedal several times with the engine off to ensure no change in pedal reserve distance, then start the engine; a slight drop in the pedal indicates normal operation. For the airtightness check, start the engine and turn it off after one or two minutes, then depress the brake pedal slowly; if the pedal depresses less each time, the booster is airtight. With the engine off, press the brake pedal several times to remove any stored vacuum in the power brake booster, then move the driver's seat to the rearmost position and disconnect the cable from the negative terminal of the battery. Remove the windshield wiper motor and the
Brake Master Cylinder, disconnect any electrical connectors attached to the power brake booster, and carefully disconnect the vacuum hose from the brake booster check valve. Inside the vehicle, remove the
Brake Light Switch, pry the retaining clip off the brake pedal pin, and disconnect the booster pushrod. Remove the booster mounting fasteners and slide the booster straight out from the firewall. For installation, follow the reverse procedures, ensuring to replace the seal between the power booster and the firewall, tighten the booster mounting nuts to the specified torque, install a new retaining clip for the booster pushrod, and bleed the brake system before testing the operation of the brakes.