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Probable
cause
I Air
leakago
at
check
valve
2
Air
leakage
a
t
push
rod seal
3
Air
leakage
between valve
body
and
seal
4
Air
leakage
at
valve
plunger
seat
5
Damaged
piping
or
joints
2
Fifteen
seconds after
engine
is
stopped
and brake
fully applied
ob
serve
the rate
of
drop
in air
pressure
registered by
vacuum
gauge
Probable
cause
1 Air
leakage
at
check
valve
2
Damaged diaphragm
3
Reaction disc
dropped
off
4
Air
leakage
at
and valve
body
poppet assembly
seat
Note
When
replacement
of any
part
is
required
be
sure
to
renew
Master
Vac
as an
assembly
Inspecting
check valve
Remove
clip
and disconnect hoses
at connections
The check
valve
can
now
be removed
yr
BA3
Fig
BR 26 Location
of
check valve
2
Using
a
Master
Vac
tester
apply
a
vacuum
pressure
of 200
mmHg
7 87
inHg
to
the port of
check
valve
on
the
Master Vac side If
a
pressure
drop
of
10
mmHg
0
3 9
inHg
is exceeded
in
1
I
I
17
I
f
I
I
I
Z
I
I
y1
I
I
I
7
I
I
I
I
I
I
I
I
I
I
y1
II
I
I
I
I
I
I
I
L
I
L
5
to
15
20
25
30
35
40
45
50
55
60
22
44
66
88
110
132
Pedal
operating
force
kg lb
BR772
Fig
BR 28
Performance
curves
of
Master Vac
Brake
System
Corrective
action
Replace
check valve
Replace
seal
Repair
or
replace
faulty
partes
Repair
or
replace
seat
Repair
or
replace
If
a
pressure
drop
of 25
mmHg
0
98
inHg
is
exceeded
refer
to
the
following
chart
to
determine the
cause
of
failure
Corrective
action
Replace
check
valve
Replace
Reinstall and check
push
rod
for
proper turn
Replace faulty
part
s
15
seconds
replace
check valve with
a
new
one
3
When pressure is
applied
to the
Master
Vac side of
check
valve
and
valve
does
not
open
replace
check
valve with
a
new
one
120 I
7IG
110 1 560
100 I
420
i
90 1 280
I
u
80 1 140
70 1
000
I I
60
850
0
0
5
a
50
710
40 570
30
430
20 280
10 140
BR 15
1
I
Manifold side
Master Yac side
1
Spring
2
Valve
BA289
Fig
BR 27 Sectional view
of
check
valve
Operating
test
1
Connect
an
oil pressure gauge in
brake
line
at
connection
on
master
cylinder
2
Install
a
spring
scale
on
brake
pedal
3
Start
engine
and increase
engine
speed
until
a vacuum
pressure of 500
mmHg 19
69
inHg
is
registered
on
vacuum
pressure gauge With
a
vacuum
pressure
of 500
mmHg 19
69
inHg
held
measure
an
oil
pressure
with
respect
to
each
pedal operating
force
Relationship
between oil
pressure
and
pedal operating
force
is
illustrated
in
Figure
BR
28
If test
results
are
not
as
specified
in
Figure
BR 28
check
Master Vac for condition
in
a manner
as
described under
Inspection
before
removal of this unit
Also check brake line for evidence
of fluid
leakage
Note
Determine
whether
malfunc
tion
occurs
in
Master Vac
or
in
check
valve
Always inspect
check
valve fiTlit
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