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Gonventional Brake Gomponents
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. lf
the pedal sinks, either the master cylinder is
bypassing internally, or the brake system (master
cylinder, lines, modulator, proportioning control
v a l v e , o r c a l i p e r s ) i s l e a k i n g .
2. Start the engine with the brake pedal pressed. lf the
pedal sinks slightly, the vacuum booster is
operating normally. lf 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 E position.
lf the brake pedal sinks more than 1O mm (3/8 in.) in
3 minutes, the master cylinder is faulty. A slight
change in pedal height when the Ay'C compressor
cycles on and off is normal. (The Ay'C compressor
load changes the vacuum available to the booster.)
Leak Test
1 . P r e s s t h e b r a k e p e d a l w i t h t h e e n g i n e r u n n i n g , t h e n
stop the engine. lf the pedal height does not vary
while pressed for 30 seconds. the vacuum booster
is OK. lf 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. lfthe pedal position does not
vary, check the booster check varve.
1 9 - 1 8
u
3. Disconnectthe brake booster vacuum hose (check
valve built-in) (A) at the booster (B) side.
4. Start the engine, and let it idle. There should be
v a c u u m a v a i l a b l e . l f n o v a c u u m i s a v a i l a b l e , t h e
check valve is not working properly. Replace the
brake booster vacuum hose and check valve, and
reresL
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 pedal is first pressed, it should be low.
On consecutive applications, the pedal height
s h o u l d g r a d u a l l y r i s e .
' lf the pedal position varies, replace the brake
booster vacuumhose/check valve assembly.
. lf the pedal position does not vary, replace the
brake booster.
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Chapters
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Troubleshooting
