Acura 3.5 RL Manual page 797

Master Cylinder/Brake Booster
Brake Booster Inspection
Functional Test
1. With the engine stopped, press the brake pedal sev-
eral 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 pedal pressed. If the pedal
sinks slightly, the vacuum booster is operating nor-
mally. If the pedal height does not vary, the booster
or check valve is faulty.
3. With the engine running, press the brake pedal light-
ly. Apply just enough pressure to hold back auto-
matic transmission creep. If the brake pedal sinks
more than 25 mm (1.0 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 nor-
mal. (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. With the engine stopped, press the brake pedal sev-
eral times using normal pressure. When the pedal is
first pressed, it should be low. On consecutive appli-
cations, the pedal height should gradually rise. If the
pedal position does not vary, check the booster
check valve.
Booster Check Valve Test
1. Disconnect the brake booster vacuum hose at the
booster.
2. Start the engine, and let it idle. There should be vac-
uum. If no vacuum is available, the check valve is
not working properly. Replace the brake booster
vacuum hose and check valve, and retest.
NOTE: '96 - 97 models shown.
BRAKE BOOSTER
VACUUM HOSE
(Check valve is
built-in)