When Not Using Measuring Device
WARNING: This page is about a different car, the 2022 Subaru WRX. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
When an operation check is performed with no measuring devices, a faulty part cannot be identified correctly. But it is possible to identify the outline of the defect by performing the check according to the following procedures.
- Air tightness check
NOTE:
- In case of defective operation, inspect the sealing surface conditions of check valve, vacuum hose, and cylinder seal assembly and vacuum booster assembly.
- If parts are damaged, or the sealing surface of the vacuum booster assembly has a defect such as flaking paint, damage or rust, it may cause negative pressure leakage. Therefore, replace the parts and perform the test again.
- If no improvement is observed, check precisely with gauges.
- Start the engine, and idle it for 1 to 2 minutes, then turn it OFF.
- Depress the brake pedal several times applying the normal pedal force.NOTE:
The pedal stroke should be the longest at the 1st depression, and it should become shorter at each successive depression.
- If no change occurs in the pedal height when pressed, the vacuum booster assembly is faulty.
- Check operation
NOTE:If a faulty part is detected after inspection, check precisely with measuring devices.
- While the engine is OFF, depress the brake pedal several times applying the same pedal force, to check for a change in pedal height.
- With the brake pedal depressed, start the engine.
- As the engine starts, the brake pedal should move slowly toward the floor. If the brake pedal height does not change, the vacuum booster assembly is faulty.
- Loaded air tightness check
NOTE:
If a faulty part is detected after inspection, check precisely with measuring devices.
- Depress the brake pedal while the engine is running, and turn the engine to OFF while the pedal is depressed.
- Keep the pedal depressed for 30 seconds. If the pedal height does not change, the function of vacuum booster assembly is normal. If the pedal height increases, it is faulty.