Brake Servo Faults & Diagnosis

Modified on Fri, 3 Feb, 2023 at 12:01 PM

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

Was this article helpful?

That’s Great!

Thank you for your feedback

Sorry! We couldn't be helpful

Thank you for your feedback

Let us know how can we improve this article!

Select at least one of the reasons
CAPTCHA verification is required.

Feedback sent

We appreciate your effort and will try to fix the article