Honda Civic Service Manual page 1179

Brake Booster InsPection
FunctionalTest
1. With the engine stopped, depress the brake pedal
several times to deplete the vacuum reservoir, then
depress the pedal hard and hold it for 15 seconds lf
t h e p e d a l s i n k s ' e i t h e r t h e m a s t e r c Y l i n d e r i s
bypassing internally, or the brake system (master
c y l i n d e r . l i n e s . m o d u l a t o r , p r o p o r t i o n i n g c o n t r o l
valve, or caliPer) is ieaking.
2.
Start the engine with the pedal depressed lf the
pedal sinks slightly, the vacuum booster is operating
n o r m a l l y . l f t h e p e d a l h e i g h t d o e s n o t v a r y , t h e
booster or check valve is faultY.
3. With the engine running. depress the brake pedal
l i g h t l y . A p p l y j u s t e n o u g h p r e s s u r e t o h o l d b a c k
a u t o m a t i c t r a n s m i s s i o n c r e e p . l f t h e b r a k e p e d a l
s i n k s m o r e t h a n 2 5 m m ( 1 . 0 i n . ) i n t h r e e m i n u t e s ,
t h e m a s t e r c v l i n d e r i s f a u l t y . A s l i g h t c h a n g e i n
pedal height when the A'lC compressor cycles on
a n d o f f i f n o r m a l . ( T h e A / C c o m p r e s s o r l o a d
changes the vacuum available to the booster')
Leak Test
1 . D e 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 .
then stop the engine. lf the pedal height does not
vary while depressed for 30 seconds, the vacuum
b o o s t e r i s O K . l f t h e p e d a l r i s e s . t h e b o o s t e r i s
faulty.
2, With the engine stopped, depress the brake pedal
s e v e r a l t i m e s u s i n g n o r m a l p r e s s u r e W h e n t h e
Dedal is first depressed, it should be low On con-
secutive applications, the pedal height should grad-
uallv rise. lf the pedal position does not vary, checK
the booster check valve.
l . /
19-23
Booster Check Valve Test
1. Disconnect the brake booster vacuum hose at the
booster.
2.
Stan the engine and let it idle. There should be vac-
uum. lf no vacuum is available, the check valve is
not working properly. Replace the brake booster
vacuum hose and check valve, and retest.
BRAKE BOOSTER
VACUUM HOSE
( C h e c k v a l v e
b u i l t - i n )