1979 DATSUN 210 low oil pressure

Engine
Tune

up

BASIC
MECHANICAL
SYSTEM

ADJUSTING
INTAKE

AND
EXHAUST

VAL
fE
CLEARANCE

Note
After

tightening
cYlinder
head

bolts

adjust
intake
and
exhaust

valve

clearances

Valve
clearance
ai
ljustment
cannot

be

made
while
the

engine
is
in

opera

tion

To

adjust
proceed
as
follows

I
Start

engine
and

warm
it

up
uritil

water

temperature
indicator

points
to

the
middle
of

gauge
Then

stop
engine

2
Rotate

crankshaft
to

bring
No
I

cylinder
in

top
dead
center
on
its

compression
stroke

3
Remove

valve
rocker

cover

Adjust
valve
clearance
at

following

four

points
while

engine
is
still
hot

CD
Exhaust
valve

of
No
I

cylinder

@
Intake
valve
of
No
I

cylinder

@
Intake
valve
of
No
2

cylinder

@
Exhaust

valve
of
No
3

cylinder

Note

Numbers
in

circle

agree
with

those
in

accompanying
sketch

tiri

Fig
ET
1

Adjusting
Value
Clearanu

4

Again
rotate
crankshaft
one
turn

so
that

No
4

piston
is
in

top
dead

center
on
its

ompression
stroke
Ad

just
following
valve

s

CID
Exhaust

valve
of
No
2

cylinder

@
Intake
valve
of
No
3

cylinder

j
Intake
valve
of
No
4

cylinder

@
Exhaust
valve
of
No
4

cylinder

Adjustment
should
be
made
while

engine
is
hot
After
all
valves
have
been

adjusted
correctly
tighten
lock

nut

firmly
to
secure
ihe

adjustment

Valve
clearance

Hot

Intake

0
35

mm
0
014

inl

Exhaust
0
35
mm

0
014

in

tJl
Tightening
torque

Valve

rocker

adjusting
nut

1
6

to
2
2

kltm

12

to
16
ft
lb

Alternator

Crankshaft

pulley

Unit
mm

in

Idler

pulley

Fig
ET
2

CHANGING
ENGINE

OIL

1

Check
if
oil
is
diluted
with
water

or

gasoline
Drain
and
refill
oil
if

necessary

Note

a
A

milky
oil
iiulicates
the

presence

of

cooling
water
Isolate
the
cause

and
take
corrective
measure

b
An
oil

with

extremely
low

viscosity

indicates
dilution
with

gasoline

2
Check

oil
level
If
below
the

specified
level
raise
it

up
to
the
H

level

3

Change
engine
oil
in

accordance

with
the
maintenance

schedule

Engine
oil

capacity

A14

With
oil
filter

3
7
liters

3
U
US

qt
3
Yo

Imp
qtl

ET3
CHECKING
AND

ADJUSTING
DRIVE

BELTS

I

Check
for

cracks
or

damage
Re

place
if

necessary

2

Normal
drive

belt
deflection
is

showndI
figure
below
when

moderate

thumb

pressure
is

applied
midway

between

pulleys

Thumb

pressure
10

kg
221bl

Idler

pulley

Compressor
p1
111ey

AC710

Checking
Drive
Belts

for
Deflection

Without
oil
filter

3
2
liters

3

USqt
2

U

ImP
ltl

A15

With
oil
filter

3
3
liters

3
US

qt
2
U

Imp
qd

Without
oil
filter

2
8
liters

3
us

qt
2

Imp
qd

REPLACING
OIL

FILTER

The
oil
filter
is
a

cartridge
type
and

can
be

removed

using
Oil
Filter

Wrench
STl9320000

I
Check
for

oil
leaks

past
gasketed

Oange
If

leakage
is

found
retighten

just
enough
to

stop
leakage
If
reo

tightening
is

no

longer
effective
re

pl
ice
mter
as

an

assembly

2

When

installing
oil
mter

tighten

by
hand

Note
Do
not

overtighten
oil
filter

lest

leakage
shoUld
occur

CHANGING
ENGINE

COOLANT

PERMANENT

ANTI
FREEZE

COOLANT

Note

The

permanent
anti

freeze

coolant
is
an

ethylene
glya
l
base

product

containing
chemical
in

hibitors
to

protect
the

cooling

system
from

rusting
and
corrosion

The
anti

freeze
does
not
cOntain

any
glycerine
or

ethyl
alcohol
It

will
not

evaporate
or
boil
a

ay
and

can
be

ilsed
with
either

high
or
low

temperature
thermostats
It

flows

freely
transfers
heat

efficiently

and
will
not

clog
the

passages
in

the

cooling

system
The
anti
freeze

must
not
be
mixed

with
other

product
This
coolant
can
be
used

throughout
the
seasons
of
the

year

Whenever
coolant
is

changed
the

cooling

system
must
be
flushed
and

refilled
with
a
new
coolant
Check
the

coolant
level

See
instructions

attached
to

the

anti
freeze
container
for

mixing
ratio

of
anti
freeze

to
water

CHECKING
COOLING

SYSTEM
HOSES

AND
CONNECTIONS

Check
hoses
and

fittings
for
loose

connections

or
deterioration
Re

tighten
or

replace
if

necessary

INSPECTION
OF
RADIATOR

CAP

Apply
reference

pressure
0

9

kgj
cm2
13

psi
to

radiator

cap
by

means
of
a

cap
tester
to

see
if
it
is

satisfactory
Replace

cap
assembly
if

necessary
I

j
ngine
Tune

up

ET012

Fig
ET

3

Testing
Radiator

Cap

COOLING
SYSTEM

PRESSURE
TEST

Witli
radiator

cap
removed

apply

reference

pressure
1
6

kgfcm2
23

psi
to
the

cooling
system
by
means

0

no

Fig
ET
4

Water

capacity
M
Tmodelsl

Without
heater

5
2
liten

5
1f
US

qt
4

Imp
qt

With
heeter

5
9
Iiten

6
4
US

qt
5

Y

Imp
qt

Water

capacity
AfT
modelsl

Without
heater

5
0
liters

5

y
US

qt
4

Imp

qt

With
heater

5
7
liten

6
US

qt
5

Imp
ill

CHECKING
ENGINE

COMPRESSION

Note

a
To
check

cylinder

compression
it
is

essential

to
remove
all

spark
plugs

The

purpose
of
this
test
is
to

ET
4
determine
whether
there
is
exces

sive

leakage

past
piston
rings
head

gasket
etc
To
test

engine
should

be
heated
to
the

operating
t
M

ture
and
throttle
valve

opened

b

Cylinder
compre
on
in

Cylinders

should
not
be
less

than
llO
of
the

highest
reading
Different

compres

sion

in
two
ore
more

cYlinder
usual

ly
indicates
an

improperly
seated

valve
or
broken

piston
ring

c
Low

compression
in

cylinders
am

result
from
worn

piston

rings
This

trouble

may
usuaDy
be
accom

panied
by
ex
ssive
fuel

consump

tion

I

Warm

up
engine
sufficiently

2

Disconnect

aU

spark

plugs

3
Disconnect
anti
dieseling

solenoid

valve
connector

4

Properly
attach
a

compression

tester
to

spark

plug
hole
in

cylinder

being
tested

FiI
ET
S
ET529

Testing
Compre
sion

Pr
s8ure

5

Depress
accelenit6r

pedal
to

open

throttle
and
choke

valves

Note
Do
not

pump
pedal

6
Start

engine
as

quickly
as

pos

sible

Compression
pressllre

kg
cm2
ii
at

rpm

Standard
13

5
192

350

Minimum
12
5

1781
350

If

cylinder

compression
in
o
e

or

more
cylinders
is
low

pour
a

small

quantity
of

engine
oil
into

cylinders

through
the

spark

plug
holes
and
retest

compression

I

If

addingoil
helps
the

compres

sion

pressure
chances
are

that

piston

rings
are

worn
or
damaged

2

If

pressure
stays
low

the
likeli

hood
is
that
valve
is

sticking
or

seating
Engine
Tune

up

improperly

3

If

cylinder
compression
in

any

two

adjacent
cylinders
is
low

and
if

adding
oil
does
not

help
the

compres
sion
there
is

leakage
past
the

gasketed

surface

Oil
and

water
in
combustion
cham

bers
can
result
from
this

problem

IGNITION
AND

FUEL
SYSTEM

CHECKING
BATTERY

I

Remove
six
vent

plugs
and
check

electrolyte
level
in
each

battery
cell
If

necessary
pour
distilled
water

Overflow
Correct

Shortage

t
t
j

t

t
t

EE358

Fig
ET
6

Checking
Electrolyte

Level
2
Measure
the

specific
gravity
of

battery
electrolyte

E
T372

Fig
ET
7

Checking
Specific
Gravity

of
Battery
Electrolyte

Over
1
22
Full

charge
value

at
200C
680F

1
28

1
26
Permissible
value

Frigid
climates

Other
climates

Note

a
Clean

top
of

battery
and

terminals

with
a

solution
of

baking
soda
and

water
Rinse
off
and

dry
with
com

pressed
air

Top
of

battery
must

be

c1
n
to

prevent
current

leakage

between
terminals
and
from

posi

tive
terminal
to
hold
down

clamp

b
In

addition
to
current

leakage

prolonged
accumulation
of
acid
and

dirt

on

top
of

hattery
may
cause

blistering
of
the
material

covering

ronnector

straps
and
rorrosion
of

straps

c
Afte
r

tightening
terminals
coat

them
with

petrolatum
vaseline
to

protect
them
from
corrosion

CAUTION

If
the

battery
cables
are
disconnected

they
should
be

tightly
clamped
to
the

battery
terminals
to
secure
a

good

contact
Over
I

20

CHECKING
AND

ADJUSTING

IGNITION
TIMING

Check

spark
plugs
for
condition

2

Thoroughly
remove
dirt
and
dust

from
crank

pulley
at

timing
mark

location

and
front
cover
at

timing

indicator

3
Warm

up
engine
sufficiently

4
Connect

engine
tachometer
and

timing
light
in
their

proper
positions

5

Adjust
idling
speed
to
the

specifi

ed
value

Idling
speed

Manual
transmission

700

pm

Automatic
transmission

6S0

rpm

in
0

position

ET
S
WARNING

When
selector
lever
is
shifted
to

0

position
apply
parking
brake

and
block
both
front
and
rear

wheels
with
chocks

Note

a
On
FU
models

set

idling
speed

with

distributor
vacuum
hose
dis

connected

b
Disconnect

distributor
vacuum

hose

at

distributor

diaphragm
side
and

plug
hose
with
blind

plug
See

Fig

ET
8

ET501

Fig
ET

B
Disconnecting
Distributor

Vacuum
Hose

6
Check

ignition
timing
with
a

timing
light
to
ensure
that
it
is

adjust

ed
to

specifications
indicated
below

Ignition
timing

Manual
transmission

SO
B
T
0
C
f700

rpm

California
FU
models

100
B
T
0
C
f700

pm

Non
California
Canada

models

Automatic
transmission

SO
B
T
0
C
f6S0

rpm

California
models

Condition

Othen

NOISY
ENGINE

Cor

knockillll

M8chanicol

knocking

Crankshaft

bearing

knocking

Connecting
rod

bearing
knocking

Piston
and

cylinder

noise

Piston

pin
noise

Water

pump
noise

Air

pump
noise

Others
Engine
Tune

up

Probable
cause

Improper
octane
fuel

Improper
tire

pressure

Dragging
brake

Dutch

slipping

Overloaded

engine

Carbon

knocking

Timing
knocking

Fuel

knocking

Preignition
miswing
of

spark
plug

This

strong
dull
noise
increases
when

engine

is
occelerated
To
locate
the

place
cause
a

misfire
on
each

cylinder
If
the
noise

stops

by
the
misfire
this

cylinder

generates
the

noise

This

is
a
little

higher
pitched
noise
than
the

crankshaft

knocking
and
also
increases

when

engine
is
accelerated
Cause
a
misfire

on
each

cylinder
and
if
the
noise
diminishes

almost

completely
this
crankshaft

bearing

generates
the
noise

When

you
hear
an

overlapping
metalic
noise

which
increases
its

magnitude
with
the

revolution
of

engine
and
which
decreases
as

engil
e
is
warmed

up
this
noise
is
caused

by

piston
and

cylinder
To
locate
the

place

cause
a
misfire
on
each

cylinder

This

noise
is
heared
at
each

highest
and

lowest
dead
end
of

piston
To
locate
the

place
cause
a
misfire

on
each

cylinder

This
noise

may
be
caused

by
worn
or

damaged
b

arings
or

by
the
uneven
surface

of

sliding
parts

Damaged
air

pump
Except
Canada
and
FU

models

An

improper
adjustment
of
valve
clearance

Noise
of

timing
chain

An
excessive
end

play
on
crankshaft

Noisy
E
F
E

valve
shaft

H20
Corrective
action

Replace
with

specified
octane
fuel

Inflate
to

sptcifled
pressure

Adjust

Adjwt

Use

right
gear
in

driving

Disassemble

cylinder
head

and
remove

carbon

Adjust
ignition
timing

Use

specified
octane
fuel

Use

specified

spark
plug

This
is
caused

by
worn
or

damaged
bearings

or

unevenly
worn
crankshaft
Renew

bearings
and

adjust
or

change
crankshaft

Check
lubrication

system

Same
as
the
case
of
crankshaft

bearings

This

may
cause
an
abnormal

wearing
of

cylinder
and
lower

compression
which
in

turn
will
cause
a
lower
out

put
power
and

excess
ive
consumption
of
oil

Overhaul

engine

This

may
cause
a
wear
on

piston
pin
or

piston
pin
hole

Renew

piston
and

piston
pin
assembly

Replace
water

pump
with
a
new
one

Repair
or

replace

Adjust

Adjust
the
tension
of
chain

Disassemble

engine
and
new
main

beaung

Repair

Condition

Faulty

connecting

rod

Faulty
crankshaft

bearing
Engine
Mechanical

Probable

cause

Shortage
of

engine
oil

Low
oil

pressure

Poor

engine
oil

quality

Rough
crankshaft
surface

Clogged
oil

passage

Bearing
worn
or
eccentric

Bearing
improperly
assembled

Loose

bearing

Incorrect

connecting
rod

alignment

Shortage
of

engine
oil

Low
oil

pressure

Poor

quality
engine
oil

Worn

or
out
of
round
crankshaft

journal

Clogged
oil

passage
in
crankshaft

Bearing
worn
or
eccentric

Bearing

inproperly
assembled

Non
co
centric
crankshaft

or

bearing

EM
33
Corrective
action

Add
or

replace
oil

Check
oil
level
on

daily
basis

Correct

Use

proper
oil

Grind
and

replace
bearing

Clean

Replace

Repair

Replace

Repair
or

replace

Add
or

replace

Check
oil
level
on
daily
basis

Adjust

Use

proper
oil

Repair

Clean

Replace

Repair

Replace

OIL

PUMP

The
oil

pump
and
filter

assembly
is

bolted
to

the

right
side

of
the

cylinder

block
and
can
be
removed

with
the

engine
in

pl
c
The
oil

pump
which
is

driven

by
a

gear
on
the
camshaft

has

the

full
flow

element

type
filter
in

stalled
to
the

oil

pump
cover

REMOVAL

I

Place
a
suitable
container

under

oil

pump

2
Remove
three

bolts

attaching
oil

pump
and
filter

assembly
and

with

draw

assembly

3

Separate
oil

filter
from
oil

pump

4

Ciean
off
old

gasket
from

mating

surfaces

i

E

L043

F
EL

2
R

moving
Oil

Pump

Asso

mbly

INSTALLATION

I

Install
oil
filter
to
oil

pump

2

Locate
oil

pump
and

filter
as

sembly
or

cylinder
block

using
a

spacer
and
new

gasket
Secure
with

three

bolts

l
l
Tightening

torque

Oil

pump
securing
bolts

0
9
to
1
4

kg
m

6
5
to
10
1
ft

lbl

3

Check
oil
level

and
add
oil
if

necessary

4

Start

engine
and

check
for
oil

leaks

5

Remove
the
container
Engine
Lubrication

System

DISASSEMBLY
AND

ASSEMBLY

I

Remove
bolt

securing

pump
cover

to

pump

body
Separate
pump
cover

from

pump
body

2

Slide
out
outer
rotor

from

pump

body

3

Remove
oil

pressure

regulator

plug
washer

shim

spring
and
valve

4

Assemble
oil

pump
in
reverse

order
of

disassembly

Note

a

When

placing
oil

pump
in

a
vice

use
extreme
care
not
to
distort

pump
body
and
cover
in
the

jaws

b
Do

not

pull
out

drive
shaft

pin

securing
drive
shaft

and
inner
rotor

Shaft
is

press
fitted
to
rotor
with

the

pin
caulked

EL044

Fig
EL
3
Oil

Pump

l
l
Tightening

torque

Oil

pump
cove
bolt

0
39

to
0

5
2

kltm

2
8

to
3
8

ti
Ib

Regulator
valve

plug

4
0
to
5
0

kltm

29
to
36
ft

bl
INSPECTION

Wash
all

parts
in

cleaning
solvent

and

dry
wiih

compressed
air

I

hispect
pump
body
and

cover

for
cracks
or
excessive
wear

2

Inspect
pump
rotors
for

excessive

wear

3
Check
inner

rotor
shaft
for

looseness
in

pump
body

4

Inspect
regulator
valve
for
wear

or

scoring

5
Check

regulator

spring
to

see
that

it
is

not
worn
on
its

side
or

collapsed

6

Using
a
feeler
gauge
check

tip

clearance

00
and
outer
rotor
to

body

clearance

CD
shown
in

Fig
EL
4

EL059

1
Outer
rotor
to

body
clearance

2

Tip
clearance

3

Gap
between

rotor
and

stnight
edge

4

Gap
between

body
and

straight
edge

ig
EL
4

Checking
Rotor

Clea
nce

7

Place
a

straight
edge
across
the

face
of

pU
mp
and

depress
it

slightly
as

shown
in

Fig
EL
4

Check

gap

@

between

body
and

straight
edge
or

gap

@
between
rotor
and

straight
edge

Gap

0
03
to
0
06
mm

0
0012
to
0
0024
in

Rotor
side
clearance
rotor
to
bot

tom

cover
clearance
with

gasket

should

satisfy
the

specifications

Standard
Wear
limit

Rotor

side
clearance

mm
in
0

04
to
0
08

rotor
to
bottom

cover

0
0016
to
0
031
0
20
0

0079

Rotor

tip
clearance

V
mm
in
Less
than

0
20
0
0079

0
12
0
0047

Outer
rotor
to

body

mm
in
0

15
to
0
21

0
50
0
0197

clearance

CD
0
0059
to
0
083

EL3

Not

Pump
rotors
and

body
are
not
serv

iced

separatdy
If

pump
rotors
or

body
are

damaged
or

worn

replace

ment
of
the
entire
oil

pump
assembly

isnecessary

OIL
PRESSURE

REGULATOR
VALVE

The
oil

pressure
regulator
valve
is

not

adjustable
At
the
released

posi

tion
the
valve

permits
the
oil
to

by

pass
through
the

passage
in
the

pump
cover
to
the
inlet
side
of

the

pump
Check

regulator
valve

spring
to

ensure

that

spring
tension
is
correct

no

1

Regulator
valve

2
Relief

valve

3
Valve

spring
E
L045

Fig
EL
5

Regulator
and
Reli
Vatv
Engine
Lubrication
System

8Peciflcatlons

Oil

pressure

At

idling

more
than

O

Blrg
an2
11

psi

At

3
000

rpm

3
B
to
5
2lrg

an2

54
to
74

psi

Regulator
ai

spring

Free

length

43
49
rom
1
7122
in

InstoJlod
l

ngth
load

30
3
mm
3
67

kg

1
193

inJB
09lbl

Regulator
val

o

ning
pressur

3

8
to
4
2

lrg
an2

54
1060

psi

OIL
PRESSURE

RELIEF
VALVE

The
relief
valve
located
in

the
oil

pump
cover

by
passes
the

oil
into
the

main
oil

gallery
when

the
oil
filter

elem
nt
is

exCessively
clogged
With

regula
tor
valve
removed
check
valve

for

operation
See

Fig
EL
5

OIL
FILTER

tEMOVAL

Place
a
suitable
container
under
the

f1lter

Unscrew
f1lter
from
oil

pump
cover

flange
using
Oil
Filter
Wrench

STl9320000

EL
4
Fig
EL
6

Removing
Oil
Filter

INSTALLAnON

I
Coat

the

packing
on
the
new

f1lter
with

oil
Position
the

f1lter
on

the
oil

pump
cover

flange
Hand

tight

en
the
f11ter
until
the

packing
contacts

the

cover

flange
then
advance
it

2
3

tum

Note
Do
not

overtighten
the
fiIter

or

oil
leak

may
occur

2

Operate
the

engine
at
fast
idle

and
check
for
oil
leaks
Check
the
oil

level
and
add
oil
if

necessary

OIL
PRESSURE

WARNING

SWITCIt

The
oil

pressure
warning
switch
is

located

on
the

oil

pump
cover
and

wired
to

an
instrument

cluster
See

Fig
EL
6

The

warning

light
glows
whenever

the

oil

pressure
drops
below
0

2
to
0
4

kg
cm1
2
8
to
5
7

psi

Prior
to

installing
a
switch
to
cover
I

be

sure
to

apply
a
conductive
sealer

to

threads
of

switch

10

Replenish
coolant
and

check
for

leaks

INSPECTION

I

Submerge
thermostat
in

hot

water
SOC
90F
above
the

specified

temperature
Refer
to
Service
Data

and

Specifications

2

After

preparing
for
the
marked

screwdriver

at
about
8

mm
0
31
in

from
the

tip
inspect
the
lift

height

H
of
valve

by

inserting
it

f

C0097

Fig
CO
g
In

pecting
Thermostat

3
Now

place
thermostat
in

water

SoC
90F
below
the

specified
temper

ature

If
thermostat
does
not

operate
at

the
above

specified
temperature
it

must
be

replaced
because
it
cannot
be

repaired

Note

If

necessary
check
a
new
ther

mostat
before

installing
it
in

the

engine

RADIATOR

The
radiator
filler

cap
is

designed
to

maintain
a

pre
set

pressure
0
9

kgfcm2

13

psi
above

atmospheric

pressure

The
relief
valve

consisting
of
a

blow
off
valve

and
a

vacuum
valve

helps
to

prevent
the

coolant
from

boiling
by
giving

pressure
to
it
How

ever
when
the

pressure
is

reduced

below

atmospheric

pressure
the
vacu

wn
valve
allows
air
to

re
enter
the

radiator

preventing
the
formation
ofa

vacuum
in
the

cooling
system

On
models

equipped
wi

th
the
au
to

malic

transmission
the
oil
cooler
is
Cooling
System

combined
with
the
radiator
to

cool

transmission

fluid

REMOVAL
AND

INSTALLATION

1
Drain

coolant
into
a

clean
con

tainer

2
Disconnect
radiator

upper
and

lower
hoses

On
models
with
automat

ic

transmission
disconnect
cooler
inlet

and
ou
tlet
lines

from
radiator

3
Rem
Ne
fan
shroud

retaining

bolts
and
remove
fan
shroud

4
Remove
radiator

retaining
bolts

and
then

remove
radiator

upward

S
I

nstaD
radiator
in

the
reverse
se

quence
of
removal
Note
the
fol

lowing

I
Insert

hoses
in
their

positions

until

they
bottom

2
Ensure
that
arrow
marks
on

hoses

are
clearly
visible
from

upper

direction

when
hoses
are
assembled

3
Ensure
that
clearance
between

radiator
hose
and

any

adjacent
parts
is

30
mm
1
18
in
min
On
air
condi

tioner

equipped
models
a
minimum

clearance
of
18
mm
0
71
in
should

exist
between

compressor
and
hose

4

Ensure
that

clearance
be
tween

shroud
and
fan
is

even
at
any
place

Note
Be
careful
not
to

damage
radi

ator
fins
and
core
tube
when
install

ing

INSPECTION

Radiator

cap
should
be
checked
for

working
pressure
at

regular
tune

up

intelVals
First
check
rubber
seal
on

cap
for
tears
cracks
or
deteriontion

after

cleaning
it
Then
ins
taD
radiator

cap
on
a

tester
If

cap
does
not
hold

or

will

not
release
at
the

specified
pres

sure

replace
cap

Fig
CO
lO

Testing
Radiator

Cap

CO
5
Also

inspect
radiator
for

leakage

using
cap
tester
and

applying
a

pres

sure
of
1

6

kgfcm2
23

psi

If

a

leakage
is
detected

repair
or

replace
radiator

ET116

Fig
CO
II

Testing
Cooling
System

Prtuurt

RADIATOR

RESERVOIR
TANK

OPERATION

The
radiator
reservoir
tank
is

mounted
to
the

right
hand
side
core

support
through
the
bracket
When

the

coolant

temperature
in
the
radiator

rises

and

pressure
builds

up
to
an

extent
the

pressure
relief
valve

provided
in

the
radiator

cap

opens
to

release
excess
coolant
into

the
re

servoir

tank
When
the
coolant

temper

ature
lowers
and

pressure
decreases
in

the
radiator
the
vacuum
valve

provid

ed

in
the
radiator

cap
opens
to
allow

the
coolant
to

re
enter
the
radiator