Toyota 4A-F Repair Manual page 28

T ile cooling sYSI(�m is composed of Ihe w,uer
lICk't Gnside the cylinder block and cylinder head),
radi3tor, waler pump, thermostat, elllCtric fan,
hoses and other components,
faon
Coolant which is heatl!ld .. the walQf Jacket is
Plimpecl to ,he radiator, Ihrough which an eleclric
blows air to cool the coolanl as il passes
through. Coo'anl which has been cooled is Ihen
senl back 10 the engine by the waler pump, where
It cools the engine.
The waHl' jacket is a network of chennels in
01 the cylinder block and cylinder head
VleII
:!waugh which coolttnt passes. It is designl!ld to
lIfOVide adequate cooling ol lhe cylinders a.e
bustlon chambe-rs which become the holtett dur o
ing engine operalion.
AADIATOR
h. MR2
\tie
The radiator p «lorms the funclion of cooling
01
coolant which has passed through the wa'er
link
�ckel and become hoL and
the
the Yehicle. The radielor consists 01 an upper
Ind lower tank. and
lisa
two tank,. The upper tank con'llins Ihe inlel
cooIlint tram Ihe wale. jacket and the filter inlel.
has a hose attechod through whioch uceu
coolant Of sleam can
me ou"et for COOlant and Ihe drein cock. The core
contains many tubn through which cootent llows
�t
trom the upper tlNlk to lhe lower Ilink al weft as
lOr
cooling lins which rediale heat aW8y from the coo­
in lhe tubeS. The .ir sucked through Ihe r&dill­
by the elflclric fen. as well as the wind gener·
ated by tha �ehicle's trayet, passes through the
radiator. cooling it.
transmissions include an lIulomatic IrllnsmisSion
fluid cooler buill inlO the lower tank of the
A 1110 with an electric motor
!&diOlor to assist the flow 01 air through the radi\!­
tor The fan ope,"tes when the coolant tem­
perature becomes high in order to prevent it from
becoming too high.
MR'
The rlldiator performs the funclion of cooling
lhe coolanl which has passed Ihrough the water
jllcket become not, and i, mounted in the Iront
end
of the vehiCle. The radiator in the MR2 is differenl
from 'hilt in other models, in thet il is a cross flow
type which the coolant IIow5 horizontally. It
In
lIeludes ,ide lanks and a core which connects
t hem. The inlet for coolant from the weter jacket
and th-e drain cock for draining out coolant lire
located in Ihe left sido lank The outlet for coolant
and an ai, drain, which facilitates lhe supply of
coolant to the engine, are located in the right side
is
II
mounted In the front
cora which conneCIS
lIow. The lower tank contains
Models wilh automatic
15
radialor.
mounled behind
lank. The core conlie , ins msny tubes through which
coolant flows from the left ,ide tank to th-e righl·
side tank 8S well es cooling fins whiCh rlldlll!S heat
away from the coolent in th-e tubes. Air sucked in
by the electric fan, BS well as the wind generated
by Ihe vehicle's tra�el, passes through the r8diB­
tor, cooliog the coolanl heated by the weter jacket
as it pas5e. Ihrough Ihe tubes in the core. Models
the
with automatic transmission inClude Bn automat ic
Iran.mission fluid cooler Incorporated into the
cooling pipes, A fan with all electric motor is
mounted behind th-e ,adi.tor to assist Ihe lIow of
air Ihrough the r
com·
the coolant lemper8ture becomes high in order to
pre�ent it from becoming too high. The radi,tor
cap is the lame as those used with ordinary �ehi­
cles, bul due to the layout of the MR2. it is Iocaled
on a coolant pipe in tha engine space,
RADIATOR CAP
The radilllor cap i, a pressure Iype can which
tion
$9als the 'lldiator, resulting in pressurization of the
tOl'
radialor as Ihe coolant expllnds. The pressuriu­
prevents the coolanl from boiling e�lIn when
the cootant temperature exceeds
t
A re�el �alye (pressl.lrilation valve) and a vacuum
I
�alve !ne9atiye pressure �alve) are built intO the
radiatOf
escape through the
pressure generated inside Ihe cooling system
exceeds the timil !coolant lemperalure:
120"C, 230
em> ,
4.3 - 14.2
vacuum valve opens to all8Yiate the vilcuum which
develops in the coolant syllem ./ter lhe engine is
stopped and the coolant lemperlliure
valye's o p ening allows the pressure in the cooling
system to return to the coolant in the reservoir
lank.
RESERVOIR
The reservoir tank is used 10 clltch coolant
which oye.flows lhe cooling ,ystsm as
yolumetric expansion when Ih-e coolant is heated.
The coolanl in Ihe reserYoir tank '1Ilurns 10 the
radiator when the coolent temperelUle drops. thus
keeping the r&diator lull 81 ell t,mas and a�oiding
needless coolanl 1055. Check lhe reservoi, lank
level to leern
lenished.
WATER PUMP
The water pump
cootant through the cooting
on Ihe froot 01 the cylinder block and driven by B
V·ribbed
adiator. The fan operate. when
cap. The relief yal�e open. and lets Sleam
overltow pi p e when the
pressura:
248�F,
-
psi .
29.4 -
TANK
the coolant needs to be rep­
,I
I'
used f(lf lorced circulation of
system.
belt,
CO·3
1 OO·C �21 2'FL
1 1 0 -
kgl
0.3 - 1.0
kPIIl. The
98. 1
drops. The
r/lSult of
�
It IS mounted