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2-18
ENGINE DESCRIPTION
ENGINE
(40)
The
cooling
system is
sealed by
a pressure
type
radiator
filler cap
which
cau ses the system
to
operate
at higher
t
han atmosphe ri c pres-
sure. The higher
pressure r
aises the boiling
point of coolant and incr eas es
t
he cooling effici-
ency of the radiator
.
Cars
equipped
wit h the
cellular type
radiato r
core
use
a 7
pounds pres-
sure cap wh
ich permits
a possible increase of
approximately
20°
F. in boiling point of .cool-
ant.
Cars equipped with
the
tube
and
fin t
ype
radiator cor e use
a
13
pound
cap
which permits
a poss
ible
increase of
approximately
30° F
.
in
boiling point of coolant.
THERMOSTAT CLO SED
BLOWQ.FF
VALVE
Figure 2-
16 -Recircu lation
,
Thermosta t Clos ed
Wh
en the
coola nt is
below normal
oper at ing
t
emp eratur e, the thermostat valve
closes
and
blocks circulati on t
hroug h
t
he radiator.
The
water
pump
pr essure forces the
coolant
through
the
by-pa ss passages to recirculate
through
the
cylind er block and
head.
See
figure 2-16. Wh
en
the
coolant in
cylinder block and head
reaches
th
e proper
temperature
the thermostat va
lve
starts t
o
open and
the circulation pro ceeds
through the radiator in the
normal way.
At
normal oper at ing te
mperatures
the
thermostat
is
full
open
.
See figure 2-17.
~
=
I
r
i
~VACUUM
VALVE
I
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OVERFLOW PIPE
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Figu re
2
-1
S-Pressure Ty pe Radiator Filler Cap
Installation
The pressu r e
t
yp e
radiator
filler
cap con-
tainsa blow off or
pr essure
valve and a vacuum
or atmospheric
valve.
See figure
2-15.
The pres-
sure valve is held against its seat by a spring
of
predetermined strength
which protects the
radiator by relieving the
pressure if
an ex-
treme
case of internal
pressu r e
should exceed
that for which the cooling
system
is designed.
The vacuum valve is held against its seat by a
light spring which
permits opening
of the valve
to
relieve
vac uum
creat ed
in the sys
tem when
it cools off
a
nd which
otherwise
might
cause
the
radiator to
collapse.
The
thermostatica lly operated
by-pass t
ype
of water
temperatu r e
contro l
permits
the en-
gine to reach its
normal
operating
tempera-
t
ures quickly,
by causing t
he water pump to
circulate
coolant through
the
engine, but not
through
the radiator during the warm-up
period. This is accomplished by a thermostat
valve located in the cylinder head water outlet,
a
nd
a fixed by-pass passage located between the
wat er outlet and the water pump inlet. See
figur e 2-16 and
2-17.
THERMOSTAT
OPEN
VENT
/
, - - - -
- - - -
- -
-
/
::~~~~---
-------~~ -
-_/
Figu
re
2-1
7 -
Nor mal
Circula tion ,
Thermostat
Open
Water entering
the cylinder
block
water
jacket from the pump
moves
to
the r
ea r end
of the block
befor e flowing upwar d
into the
cylinder
head wa
ter
jacket and t
hence forward
to the radiator. This path
of
circulation
pro-
vides
maximum a
nd un
ifor m
flow of coolant
over all water-jacketed su
rfaces.
A small vent
passage
is located forward of
n
umber
one
cylinder
to
permit
any steam
forming in the cylinder
block
water jacket to
escape into the cylinder head water jacket. See
figure
2-17.
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