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REPAI R I NSTRUCTIONS
CLEANING
The components of
the
hydraulic brake system should
be
cleaned in clean brake
flui
d
or
de nat ured alcohol
,
w
hi
ch does
not
co
ntain
benzene
(b
enzo
l)
.
Of the ex
isting kinds of
denatured alcohol being
so
ld
generally only methylated
s
pi
rit is free from benzene.
Brake fluid is
a
n
excellent but
expe
nsive cl
eaning
agent. Fro
m mo
st
vi
e
wpoints,
methylated
spi
rit
is
therefore
th
e
most
s
uitabl
e.
Petroi, w hite
spirit,
trichlorethylene
or alcohol with
benzene
mu
st
not
be
used
for
clea
nin
g
as,
like the
s
li
ghtest trace of
min
era
l
oi
l,
they attack
the
rubber
sea ls and ca use
them
to swe
ll
out.
For this
reason,
hands
s
houl
d
be washed
w ith soap and water before
the
interna
i
parts are
touched.
The mec hanic
working
with
the
hydraulic
components sho
ul
d preferab ly be
provi
ded
with
rubber g loves.
Fin
a
l
rins
in
g s ho
ul
d
take
p lace in the clean ing agent
free fro
m impu riti
es after
which the
parts can
be
dried in
th
e open air. To
precipitate
th
e
dryin
g and
co
mpl
ete
the
clean
ing
process,
f
iltered,
compressed
air free from
moi stu
re ca
n
be
used. It
is
of the
utmost
importan
ce
that no
alcoholic residue
is
left in the
system
when
filled with
brake fluid. Traces of alcohol
in the brake fluid
reduces its
boiling point
and can
result in the formation of vapour which
can affect
brake
functioning.
After being cleaning and dried, the parts should be
moistened with brake fluid,
assembled
and then the
complete
unit filled with brake fluid as
soon
as
possible in order to prevent corrosion
attacks
from
the moisture in the air. This applies to parts which
should
be
fitted
immediately in the vehicle. To
counteract corrosion on brake parts which are stored,
or for any other reason not
covered
by brake fluid,
the plungers,
cylinders
and
seals
should be coated
with
a
thin layer of lubricant
called
brake paste in-
tended for this purpose. Under no conditions
what-
soever
must other types of grease or rustproofing oil
be used.
BRAKE
FLU,
I D
Only first-class brake fluid, which is guaranteed by a
well-known manufacturer to fulfil the requirements
according to the
standard SAE
70 R 3, should be used
for the brake system. Fluids which only fulfil the re-
quirements according to SAE 70 R
l,
for example HD-
quaiity and FS-YY-H 910 A, should not be used.
Mix-
ing of brake fluids produced by different firms should
be avoided.
When the container of the master cylinder is being
filled, likewise with all work concerning connections,
etc. the greatest clea
nlin
ess
shoul
d be o bserved
in
order
to prevent dirt from getting into th
e syste m.
O
nly
clean,
unused
brake f
lu
id should be filled.
Brake fluid which is expelled
during,
for
example,
venting,
may not be put back into the system.
Af
ter use
over
a long
period,
it
is
normal
that
even
first-class brake
fl
ui
d grad ua
lly
deteriorates thro ug
h
the
absorpti
on
of
mo isture and small
impurities.
Thus,
deteriorated brake
fluid
can be recognized by the
fact that,
compared wi
th
new
brake
fluid,
it is darker
or has changed
its
colour, is relatively odourless and
watery, i.e
.
when felt between the
fingers
it
lacks
the
normal feeling of a
li
ght lubricat.ing film
.
Such brake
fluid sho
ul
d
be
replaced
by
new fluid, and this should
also be done when the master cylinder and
wheel
brake units are being
ove
rhauled.
FAUtT TRACING
The fo
llowin
g fau
lt
tracing
procedure can
be
used,
for
examp le
,
after
the
d iscovery, fo
ll
owing upon some
kind
of brake testing, that the
capacity of
the
foot-
brake
syste
m
is
not
what it
shoul
d
be.
Fault
tracing
can also
be carried
out
with
a
vi
e
w to
preventing
faults
arising.
l.
Check
that the level of the
brake
fluid
reaches
up to the "Max" mark on the
container. Top
up,
if
necessa ry.
See
under
the
heading "Brake
Fluid".
2.
Remove both the inside venting
nipples at one
of the front brake
calipers
a
nd connect up the
testing
device
SYO
2741
s
hown in Fig
.
5-2.
3.
Depress
the brake pedal
several
times to
even
out
any partiai
vacuum
in the servo brake
cylinder
and in this way disconnect it. Check that when free
the brake
pedal
is about level with the clutch
pedal.
4.
Apply and release the footbrake while
reading
off the pressure gauges of the testing device.
The
pressure in both the circuits
should
be observed.
At 100 kg/cm
2
(1422 Ib/sq.in.), there must not be a
difference in pressure of more than
3
kg/cm
2
(42.7 Ib/sq.in.)
.
5. With the help of a pedal jack apply the foot-
brake to
a
hydraulic brake pressure of about
100 kg/cm
2
(1422 Ib/sq.in.). Check the lines
and
parts for damage and leakage. The pressure
should
remain unchanged for at least 15 seconds.
6. Remove the pedal jack. Depress the brake pedal
and maintain this pressure. Start the engine. Here
a noticeable lowering of
the
pedal should be
felt
when the servo
cylinder starts
to operate.
7. Stop the engine af ter it has run at least
l
minute.
With the help of the pedal jack apply a hydraulic
5:3
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