Tuesday, July 15, 2008

Check vacuum assisted brake system integrity

  • With vacuum depleted from the system and with moderate steady force applied, the brake pedal does not travel towards the floor when the engine is started;
  • If the vehicle is fitted with a low vacuum indicator, the indicator does not activate at a vacuum level of 25 kPa or more;
  • With the engine stopped, one application of the service brake with a moderate pedal force results in the low vacuum indicator coming on;
  • If a trailer is connected to the motor vehicle, the trailer vacuum brakes cannot be applied from the normal driving position;
  • A brake pedal that is held depressed while the engine is running, tends to rise when the engine is stopped;
  • Vehicle is not fitted with at least one vacuum storage reservoir or tank;
  • reservoir or tank for vacuum is not protected by a check valve;
  • Vacuum is not available as soon as the engine starts, or build up time to reach the low vacuum mark (to deactivate the warning device) is longer than 30 seconds;
  • Time taken for vacuum to reach normal working level when the vacuum reserve is fully depleted is longer than 60 seconds;
  • The vacuum warning device (if fitted) does not deactivate when the low mark is reached;
  • The loss of vacuum from its maximum indicated level exceeds 125mm Hg in 10 minutes when the engine is stopped;
  • With the engine stopped and vacuum at its maximum indicated level, the vacuum gauge reading does not fall progressively with every application of the service brake;
  • the engine stopped, there is insufficient level of vacuum to allow at least two assisted service brake applications.

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