Cadillac 54-6219 1954 Shop Manual page 148

9-3
B k K S
on cars equipped with thc Factory :nstalaed Power
Brake, is 71k' lower than that on cars withno: this
accessory.
The Power drake, Fig. 9-1,
con.ssrs
of three basic
anus, ocsig:ted
to
fonctinn as a single assembly
slid controlled
by hydraulic Prcss,a rc deve lonetl
in tale master cylinder. These three unit.s are,
1.
A
vacuum 05cr cvliier which contains a
P1.50
In and a push rod wb]acL cuonects the vactltcn
piston to the ljydrsolic
piston an the hydraulic
cylinder.
1. A ijydar-ulic cylinder which contains a piston
with a
I:
heck valve.
3. A hydraulically actuated vactlomcontrul vave
whjch regcla:es the dcgroc of brake application or
release. mis control yMca consIsts of a hydrau
lically a,tn:aled piston, a diapljragin, andanutmos-
phn ne and v a: oum poppet,
Manifold vacciinl is dtrected to chic Exiwer brake
cdnder :hrnl];h a hose attached to the front of the
intake ]Jianifold. A check vs lye
ill
ibc Idle between
the intake nrnnifn Id a nh
the power r ak
a>
serves a
dual
fanlciioi;t
It prevents da
Filagu to
the power brake !n the
ovont of an er4ine backfire.
2, it traps va:au ni in the
unit at
cIte ltiliest
manifold
depression
under nnoc-.tiFig cnnditinns
usually i.c to 11 lncbee. This trapped vacuum is
sufficient to jiiakc at icuat tine brake stop with
power lassist even when nionild
vacuum u5;er:.
law or non-existent.
a..:
teil ch..k
and the power piston, Fig. 9-2, are exposed
manifold vacuum
As ide brakc pcdad is depressed, the hydraucic
pressure developed
an the
master :ylinder ia
transmitted to the power b rake I jydra 0 Inc cylinder
aod
to
the hydraulic piston in the vacuum corirot
valve, .As the hydraulic pistoli in tile ljydiadlic
cyii'adcr ts againSt the stnp wa.sher when the reds a
is fire, depressed the check ball in the piston is
heLd off Cd it.: Scot by the hydrao :ic pistnn yoke.
Fig. 9_S. ibis a
:*
loss fluid from the moeter cylinder
to
pass through
ito piston directis to th'c
wdcca
cv]ijjdcra.
nba
safety feature permit.s normal
operation of the standard brake .swtanc when ihe
oligilie is not. runniog or in 'he event that the power
syarrni ehc,uitl fail.
hluid under prnssu re is also directed to the
hydraulic piston in the vac.uc]n c:ttl:rol valec. As
fig. 7-3 hyd:a:.Iir P;.,,on Aaembty
tn
Moiper
Cylind.r Pteseure
When :115: brake pedal is in the relcssedpositaou,
the arcaa Oil bull] sides of the vacullm diaparagln
AREA
/
-AREA
Ahsosphe,ir Poppet
tImed
-
Yotuom Poppet Cloied
AP,aoiphe;it Poppet
Open
Atninipheric
Prtsvre
a.
Ped& Moving
bow,,
-
Crnbiied Preliorel
'a
-
V at U 11th
.1
AREA
A'
Mntrar Clyinder
Prestj,re
Ptetare
Og. 9-2 Pose:
.Sioce Opecoilon
-
Peleoied P,aiitia,
Fig.
c-a
Pa-ear Brake Orsiaiic,
-
traktt AppIi.d