Using Gauges

INSPECTION
OPERATION CHECK (WITH GAUGES)

CAUTION: When checking operation, be sure to securely apply the hand brake.

- Checking with gauges





Connect gauges as shown in Figure. After bleeding air from pressure gauges, proceed to each check.
- Air tightness check





1. Start engine and keep it running until a vacuum of 66.7 kPa (500 mm-Hg, 19.69 inch-Hg) = point A is indicated on vacuum gauge. Do not depress brake pedal.
2. Stop engine and watch the gauge. If the vacuum drop range is less than 3.3 kPa (25 mm-Hg, 0.98 inch-Hg) within 15 seconds after stopping engine, brake booster is functioning properly. If defective, the cause may be one of those listed below.
- Check valve malfunction
- Leak from vacuum hose
- Leak from the shell jointed portion or stud bolt welded portion
- Damaged diaphragm
- Leak from valve body seal and bearing portion
- Leak from plate and seal assembly portion
- Leak from poppet valve assembly portion
- Loaded air tightness check





1. Start engine and depress brake pedal with pedal force of 196 N (20 kg, 44 lbs.). Keep engine running until a vacuum of 66.7 kPa (500 mm-Hg, 19.69 inch-Hg) = point B is indicated on vacuum gauge while the pedal is still depressed.
2. Stop engine and watch vacuum gauge. If the vacuum drop range is less than 3.3 kPa (25 mm-Hg, 0.98 inch-Hg) within 15 seconds after stopping engine, brake booster is functioning properly. If defective, refer to "AIR TIGHTNESS CHECK". Under Without Using Gauges. Without Using Gauges

- Lack of boosting action check





Turn off engine, and set the vacuum gauge reading at "0". Then, check the fluid pressure when brake pedal is depressed. The pressure must be greater than the standard value listed.
- Boosting action check





Set the vacuum gauge reading at 66.7 kPa (500 mm-Hg, 19.69 inch-Hg) by running engine. Then, check the fluid pressure when brake pedal is depressed. The pressure must be greater than the standard value listed.