Pilot 2WD V6-3.5L (2006)
Vacuum Brake Booster: Testing and Inspection
Brake Booster Test
Functional Test
1. With the engine stopped, press the brake pedal several times to deplete the vacuum reservoir, then press the pedal hard, and hold it for 15 seconds.
If the pedal sinks, either the master cylinder is bypassing internally, or the brake system (master cylinder, lines, modulator, or caliper) is leaking.
2. Start the engine with the brake pedal pressed. If the pedal sinks slightly, the vacuum booster is operating normally. If the pedal height does not
vary, the booster or check valve is faulty.
3. With the engine running, press the brake pedal lightly, and shift the transmission to the D position. Apply just enough pressure to hold back
automatic transmission creep. If the brake pedal sinks more than 10 mm (3/8 inch) in 3 minutes, the master cylinder is faulty. A slight change in
pedal height when the A/C compressor cycles on and off is normal. (The A/C compressor load changes the vacuum available to the booster.)
Leak Test
1. Press the brake pedal with the engine running, then stop the engine. If the pedal height does not vary while pressed for 30 seconds, the vacuum
booster is OK. Does the pedal height rises go to step 6. If it does not rise go to step 2.
2. Start the engine and let it idle for 30 seconds. Turn the engine off, and wait 30 seconds. Press the brake pedal several times using normal pressure.
When the pedal is first pressed, it should be low. On consecutive applications, the pedal height should gradually rise. Does the pedal rise on each
consecutive application? If it rises the booster is OK. If it does not go to step 3.
3. Disconnect the brake booster vacuum hose (A) at the booster. The check valve (B) is built into the hose.
4. Start the engine, and let it idle. There should be vacuum available. If no vacuum is available, the check valve is not working properly. Replace the
brake booster vacuum hose and check valve, and retest. If vacuum is found, go to step 5.
5. Reconnect the brake booster vacuum hose.
6. Start the engine, and then pinch the brake booster vacuum hose between the check valve and the booster.
7. Turn the engine off and wait 30 seconds. Press the brake pedal several times using normal pressure. When the pedal is first pressed, it should be
low. On consecutive applications, the pedal height should gradually rise.
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If the pedal position does not vary inspect the seal between the master cylinder and booster. If the seal is OK, replace the brake booster.
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If the pedal position varies, replace the brake booster vacuum hose/check valve assembly.
