Also, the power brake booster unit does not need any special maintenance, but it may require a regular check on vacuum hose and its casing. To check if it is working properly press the pedal without starting the engine for several times; there should be no change in pedal reserve distance. Next, push the pedal and start your engine. If it slightly goes down, then everything is alright. For air tightness inspection, start an engine and switch off after one or two minutes of running. Then slowly depress the pedal. If on first depression the pedal goes further down and then gradually rises on second and third depressions means that booster is airtight. In addition to that, with your engine running,repeatedly press the brake pedal down until you stop the car by depressing the brake pedal at once,till when you have held down for 30 seconds without any change in reserve travel of pedal,this booster is airtight.In case this booster has malfunctioned ,it cannot be repaired but must be changed with a new or rebuilt unit. To take out this booster disconnect vacuum hose ,remove master cylinder as well.Then inside vehicle remove cotter pin,pushrod clevis pin to unlock brake booster pushrod clevis from behind brake pedals.Lastly remove four nuts from firewall that holds back up into place.Remove those four nuts from back side of firewall.Relatively speaking,it is simple for installation though tightening of those nuts which hold this booster against dashboard must be done.If new power brake boosters are being used,the length of push rod can be adjusted by turning it to right position using adjusting nut which will eventually lock nut.To complete,the last thing to do before hitting road again would be bleeding brakes again.