higher coolant boiling point allowing increased radi-
ator cooling capacity. The cap contains a spring-
loaded pressure relief valve. This valve opens when
system pressure reaches the release range of 124-to-
145 kPa (18-to-21 psi).
A rubber gasket seals the radiator filler neck. This
is done to maintain vacuum during coolant cool-down
and to prevent leakage when system is under pres-
sure.
OPERATION
A vent valve in the center of the cap will remain
shut as long as the cooling system is pressurized. As
the coolant cools, it contracts and creates a vacuum
in cooling system. This causes the vacuum valve to
open and coolant in reserve/overflow tank to be
drawn through connecting hose into radiator. If the
vacuum valve is stuck shut, or overflow hose is
kinked, radiator hoses will collapse on cool-down.
RADIATOR
DESCRIPTION
The radiator is a aluminum cross-flow design with
horizontal tubes through the radiator core and verti-
cal plastic side tanks.
OPERATION
The radiator supplies sufficient heat transfer using
the cooling fins interlaced between the horizontal
tubes in the radaitor core to cool the engine and
automatic transmission oil (if equipped).
WATER PUMP
DESCRIPTION
The water pump is located on the engine front
cover, and has an integral pulley attached (Fig. 8).
The water pump impeller is pressed onto the rear
of a shaft that rotates in a bearing pressed into the
water pump body. The body has a small hole for ven-
tilation. The water pump seals are lubricated by
Fig. 5 Thermostat Cross Section View 4.7L
1 – FROM HEATER
2 – FROM RADIATOR
3 – TO WATER PUMP
4 – ENGINE BYPASS
5 – THERMOSTAT
Fig. 6 Radiator Pressure Cap—Typical
1 – FILLER NECK SEAL
2 – VACUUM VENT VALVE
3 – PRESSURE RATING
4 – PRESSURE VALVE
DN COOLING SYSTEM 7 - 5
DESCRIPTION AND OPERATION (Continued)
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