
The c oolant outlet is located at the front of the inlet
manifold.
The thermostat is housed between the coolant
outlet and the inlet manifold.
Figure 6B1-1-4
A wax pellet type thermostat is used in the coolant
outlet passage to control the flow of coolant,
providing fast engine warm up and regulating
coolant temperature. The wax pellet or power
element in the thermostat, expands when heated
and contracts when cooled. The wax pellet is
connected through a piston to a valve and when the
pellet is heated, pressure is exerted against a metal
valve which is forced to open. As the pellet is
cooled, the contraction allows a spring to close the
valve. Thus, the valve remains closed while the
coolant is cold, preventing circulation of coolant
through the radiator, but allowing the coolant to
circulate throughout the engine to warm it quickly
and evenly.
As the engine becomes warm, the pellet expands
and the therm ostat opens, perm itting the coolant to
flow through the radiator where heat is passed
through the radiator walls. This opening and c los ing
of the thermostat valve permits enough coolant to
enter the radiator to keep the engine within
specified temperature limits.
Figure 6B1-1-5
A radiator cap, fitted to the radiator filler neck,
causes the cooling system to operate at higher
than atmospheric pressure. The higher pressure,
raises the boiling point of the coolant, resulting in
increased engine cooling efficiency.
The radiator cap contains a pressure valve and a
vacuum (atm ospheric) valve. T he pressure valve is
held against its seat by a spring, which determines
the maximum operating pressure of the cooling
system (135 kPa for V6 engine) The vacuum valve
is held against its seat by a light spring. The
vacuum created during cool down over-comes the
spring force and opens the valve, preventing the
radiator hoses from collapsing. Figure 6B1-1-6
NOTE:
Due to the cooling system pressure on vehicles
with V6 engine being greater than vehicles with V8
engine, a specific radiator cap is used on vehicles
fitted with V6 engines and will not fit onto the V8
type radiator neck.
The radiator cap for V6 is stamped with a 135 kPa
pressure rating.