Jeep Cherokee 2000 Service Manual - page 262
RADIATOR
DESCRIPTION
CAUTION: Plastic tanks, while stronger than brass,
are
subject
to
damage
by
impact,
such
as
wrenches.
Radiators for both engines are the cross flow type.
Plastic tanks are used on all radiators.
RADIATOR PRESSURE CAP
DESCRIPTION
All radiators are equipped with a pressure cap.
This cap releases pressure at some point within a
range of 83-110 kPa (12-16 psi). The pressure relief
point (in pounds) is engraved on top of the cap (Fig.
9).
The cooling system will operate at pressures
slightly above atmospheric pressure. This results in a
higher coolant boiling point allowing increased radi-
ator cooling capacity. The cap contains a spring-
loaded pressure relief valve that opens when system
pressure reaches release range of 83-110 kPa (12-16
psi).
A rubber gasket seals 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 cap allows a small
coolant flow through cap when coolant is below boil-
ing temperature. The valve is completely closed when
boiling point is reached. As the coolant cools, it con-
tracts and creates a vacuum in the cooling system.
This causes the vacuum valve to open and coolant in
the reserve/overflow tank to be drawn through its
connecting hose into radiator. If the vacuum valve is
stuck shut, the radiator hoses will collapse on cool-
down.
Fig. 8 Cross Flow Radiator
1 – RADIATOR
Fig. 9 Radiator Pressure Cap and Filler Neck—
Typical
1 – FILLER NECK SEAL
2 – VACUUM VENT VALVE
3 – PRESSURE RATING
4 – PRESSURE VALVE
XJ
COOLING SYSTEM
7 - 5
DESCRIPTION AND OPERATION (Continued)