Depress the footbrake pedal several times to dissipate the vacuum in the servo unit, then remove the brake fluid reservoir filler cap and draw off the fluid using a syringe or flexible plastic bottle, taking care not to spill any on the car's paintwork; if spilled, wash it off immediately with copious amounts of cold water. Refit the filler cap while disconnecting the wiring for the fluid level warning circuit. Place some rags beneath the master cylinder, unscrew the brake pipe union nuts, and pull the pipes just clear of the master cylinder, plugging the ends of the pipes or covering them with masking tape. If applicable, disconnect the wiring from the brake light switch, then unscrew the mounting nuts and withdraw the master cylinder from the front of the servo unit, removing the seal. Refitting is a reversal of removal, ensuring to always fit a new seal, and finally bleed the hydraulic system.