Brake Booster Test - Honda 2004 Odyssey Service Manual

Brake Booster Test

Functional Test
1. With the engine stopped, press the brake pedal
several times to deplete the vacuum reservoir, then
press the brake pedal hard and hold it for
15 seconds. If the brake 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 in.) 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. If the pedal rises, the booster is faulty.
2. 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. If the pedal position does not
vary, check the booster check valve.
3. Disconnect the brake booster vacuum hose at the
booster (A). The check valve (B) is built into the
hose.
B
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.
5. Start the engine, and then pinch the brake booster
vacuum hose between the check valve, and the
booster.
6. Turn the engine off, and wait 30 seconds. Press the
brake pedal several times using normal pressure.
When the brake pedal is first pressed, it should be
low. On consecutive applications, the brake pedal
height should gradually rise.
• If the pedal position does not vary, replace the
brake booster.
• If the pedal position varies, replace the brake
booster vacuum hose/check valve assembly.
A
19-17