(5) Install drive belt. See Accessory Drive Belts
this group.
(6) Install right front lower fender shield.
(7) Refill Cooling System. See Refilling Cooling
System in this section.
ENGINE THERMOSTATS
The 2.2 and 2.5L engine thermostats are located on
the front of the engine (radiator side) in the water
box which is part of the cylinder head construction
(Fig. 9). Turbo III thermostat is located in the water
box located on the driver side of the cylinder head
(Fig. 10).
These thermostats do not have an air bleed notch.
The 3.0L engine thermostat is located in a water
box, formed in the timing belt end of the intake man-
ifold. This thermostat has an air bleed valve, located
in the thermostat flange (Fig. 11).
The 3.3/3.8L engine thermostat is located in a wa-
ter box, formed in the drive belt side of the intake
manifold (Fig. 13).
DESCRIPTION AND OPERATION
The engine cooling thermostats are wax pellet
driven, reverse poppet choke type. They are designed
to provide the fastest warm up possible by prevent-
ing leakage through them and to guarantee a mini-
mum engine operating temperature of 88 to 93°C
(192 to 199°F). They also automatically reach wide
open so they do not restrict flow to the radiator as
temperature of the coolant rises in hot weather to
around 104°C (220°F). Above this temperature the
coolant temperature is controlled by the radiator,
fan, and ambient temperature, not the thermostat.
OPERATION AND TESTING
The thermostat is operated by a wax filled con-
tainer (pellet) which is sealed so that when heated to
a predetermined temperature. The wax expands
enough to overcome the closing spring and water
pump pressure, which forces the valve to open. Cool-
ant leakage into the pellet will cause a thermostat to
fail open. Do not attempt to free up a thermostat
with a screwdriver.
The open too soon type failure mode is included in
the onboard diagnosis. The check engine light will
not be lit by an open too soon condition. If it has
failed open, code 17 will be set. Do not change a ther-
mostat for lack of heat by gauge or heater perfor-
mance, unless code 17 is present, see diagnosis for
other probable causes. Failing shut is the normal
long term mode of failure, and normally, only on
high mileage vehicles. The temperature gauge will
indicate this, Refer to diagnosis in this section.
REMOVAL
(1) Drain cooling system down to thermostat level
or below.
(2) Remove thermostat housing bolts and housing
(Figs. 9, 10, 11 and 13).
(3) Remove thermostat, discard gasket and clean
both gasket sealing surfaces.
INSTALLATION—2.2/2.5L AND TURBO III
ENGINES
Place a new gasket (dipped in clean water) on wa-
ter box surface, center thermostat in water box on
gasket. Place housing over gasket and thermostat,
making sure thermostat is in the thermostat hous-
ing. Bolt housing to water box (Figs. 9 and 10).
Tighten bolts to 28 N
Im (250 in. lbs.). Refill cooling
system (see Refilling System).
INSTALLATION—3.0L ENGINE
Center thermostat in water box pocket. Check that
the flange is seated correctly in the countersunk por-
tion of the intake manifold water box (Figs. 11 and
12). Install new gasket on water box. Install housing
over gasket and thermostat and tighten bolts to 12
N
Im (133 in. lbs. torque).
Fig. 9 Thermostat, Housing, and Water Box—2.2/
2.5L Engine
Fig. 10 Thermostat, Housing, and Water Box—Turbo
III
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COOLING SYSTEM
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