Grand Prix V6-191 3.1L VIN M SFI (1998)
Radiator Cap: Description and Operation
RADIATOR FILLER CAP
The crossflow radiator uses a pressure-vent filler cap to allow a buildup of 103 kPa (15 psi) in the cooling system. The cap allows the system to
operate at a higher than atmospheric pressure. This pressure raises the boiling point of the coolant to about 129°C (265°F) at sea level, which increases
the cooling efficiency of the radiator.
The pressure-type cap contains a blowoff (pressure) valve (2) and a vacuum (atmospheric) valve (1). A spring of predetermined strength holds the
pressure valve against the valve's seat. This spring protects the radiator by relieving any pressure that exceeds design limits. A spring holds the
vacuum valve against the valve's seat which permits opening of the valve in order to relieve vacuum created in the system when the system cools. This
prevents radiator collapse.
CAUTION: To avoid being burned, do not remove the radiator cap or surge tank cap while the engine is hot The cooling system will release scalding
fluid and steam under pressure if radiator cap or surge tank cap is removed while the engine and radiator are still hot. As long as there is pressure in
the cooling system, the temperature can be considerably higher than the boiling temperature of the solution in the radiator without causing the solution
to boil. Removal of the pressure cap while the engine is hot and pressure is high will cause the solution to boil instantaneously - possibly with
explosive force - spewing the solution over the engine, fenders and the person removing the cap.
The radiator cap is designed to discourage unintentional removal. Safely remove the cap in the following way:
1. Slowly rotate the cap counterclockwise, do not press down, to the detent.
2. Allow any residual pressure, indicated by a hissing sound, to be relieved.
3. After the hissing stops, continue to rotate the cap counterclockwise until the cap is removed.
The following is embossed on the cap:
^
A caution regarding opening of the cap
^
Arrows that indicate the proper closed position
