Functional Test
- Start engine. Turn ignition off. Depress brake pedal several times. Depress pedal firmly and hold pressure for 15 seconds. If pedal sinks, master cylinder, brakeline or wheel cylinder is faulty.
- With pedal depressed, start engine. If pedal sinks slightly, vacuum unit is working properly. If pedal height does not vary, booster or check valve is faulty.
- With engine running, depress brake pedal lightly. Apply just enough pressure to hold back automatic transmission creep. If brake pedal sinks more than .40" (10 mm) for all models except Civic, or 1" (25 mm) for Civic in 3 minutes, master cylinder is faulty. Slight change in pedal height when A/C compressor cycles on and off is normal.