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7 - 10
COOLING SYSTEM
•
WATER PUMP
INSTALLATION
(1) U s i n g a new gasket, i n s t a l l t h e w a t e r pump.
T i g h t e n m o u n t i n g bolts to 4 1 N»m (30 ft-lbs) torque.
(2) Spin t h e water pump t o ensure t h a t t h e impel-
ler does n o t r u b against the c h a i n case cover.
(3) Connect radiator lower hose, bypass hose and
heater r e t u r n hose t o water p u m p .
(4) I n s t a l l power steering p u m p a n d bracket.
(5) I n s t a l l a i r pump and bracket.
(6) I n s t a l l alternator.
(7) I n s t a l l front bracket t o a l t e r n a t o r a n d a i r con-
d i t i o n i n g compressor or idler p u l l e y . T i g h t e n bracket
m o u n t i n g bolts to 68 N n n (50 f t . lbs.) torque. T i g h t e n
the bolts t h a t mount t h e bracket a n d water p u m p to
41 N*m (30 f t . lbs.) torque.
(8) I n s t a l l water p u m p pulley, viscous fan assembly
or spacer a n d fan shroud.
(9) I n s t a l l accessory drive belts. Refer to "Accessory
D r i v e B e l t " section o f t h i s m a n u a l .
(10) F i l l cooling system. Refer t o " R e f i l l i n g Cooling
System" section i n t h i s group.
ENGINE THERMOSTAT
The thermostat is located beneath the t h e r m o s t a t
housing a t t h e front o f the i n t a k e m a n i f o l d (Fig. 4).
The thermostat has a n air bleed notch.
HOUSING
Fig. 4 Thermostat—All Engines
DESCRIPTION
AND
OPERATION
The thermostat is a wax pellet d r i v e n , reverse pop-
pet choke type. The wax pellet i s located i n a sealed
container a t the spring end o f t h e thermostat. W h e n
heated, the pellet expands, overcoming closing spring
tension and water pump pressure t o force t h e valve
to open. Coolant leakage i n t o t h e pellet container
w i l l cause t h e thermostat t o f a i l i n t h e open position.
Thermostats very r a r e l y " s t i c k " . D o n o t a t t e m p t t o
free a thermostat w i t h a p r y i n g device.
The thermostat controls t h e operating temperature
of the engine by c o n t r o l l i n g t h e amount o f coolant
flow to the radiator. T h e t h e r m o s t a t is closed below
88°C (192°F). When t h e coolant reaches t h i s temper-
ature, the thermostat begins t o open a l l o w i n g coolant
flow to t h e radiator. T h i s provides
quick engine
warm-up a n d overall temperature control. T h e t h e r -
mostat is designed t o provide a m i n i m u m engine op-
e r a t i n g temperature range o f from 88 to 93°C (192 to
199°F) a n d t o be f u l l y open for m a x i m u m coolant
flow d u r i n g operation i n h o t a m b i e n t temperatures o f
approximately 104°C (220°F). Above 104°C (220°F)
coolant temperature is controlled b y t h e radiator, fan
and ambient temperature.
A n arrow plus the w o r d U P stamped on the f r o n t
flange
next t o the a i r bleed and t h e words T O R A D
stamped o n one a r m o f t h e thermostat, indicate t h e
proper i n s t a l l e d position.
The same thermostat is used for w i n t e r and sum-
mer seasons. A n engine should n o t be operated w i t h -
out a thermostat, except for servicing or testing.
Operating w i t h o u t a t h e r m o s t a t causes longer engine
w a r m u p t i m e , unreliable w a r m u p performance, i n -
creased exhaust emissions, and crankcase
condensa-
t i o n t h a t can result i n sludge formation.
CAUTION: Do not operate an engine without a ther-
mostat, except for servicing or testing.
TESTING
The on-board diagnostics include a mode for a t h e r -
mostat open too soon f a i l u r e condition. The check en-
gine
l i g h t w i l l not be l i t b y a n open too soon
condition, b t i t i f i t has failed open, code 17 w i l l be
set. Do not change a t h e r m o s t a t for lack o f heat b y
gauge or heater
performance
unless
code 17 i s
present.
Refer to "Diagnosis"
for other
probable
causes.
The more common type o f thermostat failure, usu-
a l l y found o n h i g h milage vehicles, i s a thermostat
failed i n t h e shut position. The temperature gauge ( i f
equipped) w i l l give a n i n d i c a t i o n of t h i s condition.
Depending upon length o f t i m e t h a t the vehicle is op-
erated, t h e pressure cap m a y vent, expelling steam
and coolant t o the coolant reserve bottle and t o t h e
surface below t h e vehicle. Refer t o t h e "Diagnosis"
section o f t h i s group.
The thermostat opening a n d f u l l open conditions
can also be tested.
Remove t h e thermostat. Refer to "Thermostat Re-
m o v a l " section i n t h i s group. Insert a 0.076mm
(0.003-in) feeler gauge, w i t h a w i r e or s t r i n g a t -
tached, between the thermostat valve and seat (Fig.
5).
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