Brake Booster Function Check

Precautions: Precautions for Brake Service · Precautions for Brakes · General safety (00)

NOTE:

Check that no air is in hydraulic line before this check.

Air Tightness Check

1)Start engine.

2)Stop engine after running for 1 to 2 minutes.

3)Depress brake pedal several times with the same force as in ordinary braking to see how pedal travel changes. Brake booster is air tight if pedal travel decreases every time the pedal is depressed.

1.	1st	3.	3rd
2.	2nd

4)If pedal travel does not change, brake booster is defective in air tightness.

NOTE:

If faulty condition is found, check vacuum lines and sealing parts, and replace the faulty part. After this, repeat the entire test.

1.	1st, 2nd, 3rd

Operation Check

1)With engine stopped, depress brake pedal several times with the same force and check that pedal travel does not change.

2)Start engine while depressing brake pedal. If pedal travel increases a little, brake booster operation is satisfactory. No change in pedal travel indicates malfunction of brake booster.

Air Tightness Check under Loaded Condition

1)With engine running, depress brake pedal. Then stop engine while holding brake pedal depressed.

Hold

2)Hold brake pedal depressed for 30 seconds. If pedal height does not change, brake booster is in good condition. If pedal height changes, brake booster is not in good condition.

Hold

30 seconds