To test the operation of the booster unit, depress the
Brake Pedal four or five times to dissipate the vacuum, then start the engine while keeping the brake depressed; there should be a noticeable give in the brake pedal as vacuum builds up. Allow the engine to run for at least two minutes, then switch it off. If the brake pedal is depressed again, a hiss from the booster should be audible, and after four or five applications, no further hissing should be heard, with the pedal feeling harder. Before assuming a problem exists in the booster unit, inspect the non-return valve. To remove the booster unit, first remove the master cylinder, then disconnect the electrical connector from the brake booster solenoid on vehicles with TCS, and remove the mounting screws at the firewall for models with cruise control to set the actuator aside. Release the cover on the hydraulic control unit and disconnect the electrical connector, then remove the brake pipes to the hydraulic control unit, capping the ends to prevent dirt contamination. Remove the securing bolts from the hydraulic unit and unclip the brake lines from the retaining clips on the firewall. Access the brake pedal by removing the driver's lower dash panel, then depress the clip and remove the pin from the booster actuator rod, followed by removing the four nuts from the booster unit mounting bracket above the pedals. Withdraw the booster unit from the firewall and engine compartment, taking care not to damage any other components, noting that the booster unit cannot be disassembled for repair or overhaul and must be replaced if faulty. For installation, reverse the removal procedure, ensuring to compress the actuator rod into the brake booster before replacement, correctly position the gasket on the booster, and test the brakes carefully before returning the vehicle to normal service.