COMMON BRAKE SERVO FAULTS

EXCESSIVE PEDAL TRAVEL

  • External leak between master cylinder and servo or between servo and wheel cylinder
  • Leakage past the rubber cup on servo valve operating piston
  • Leak between servo push rod and push rod seal

GRABBING BRAKES

  • Excessive friction between servo vacuum piston and vacuum shell
  • Excessive friction between servo valve operating piston and body

HARD PEDAL

  • Low vacuum from engine from collapsed, restricted or disconnected vacuum line from manifold
  • Air valve or vacuum valve not seating properly
  • Air leak past cup or seal on vacuum piston
  • Faulty gasket under diaphragm or between slave cylinder and vacuum shell
  • Blockage of breather slot in vacuum shell