Diagnosis And Testing: DEAERATION
As air is removed from the cooling system, it gathers in the pressurized coolant bottle. This pressure is released into the atmosphere through the pressure valve located in the radiator pressure cap when pressure reaches 21 PSI (145 kPa.).
NOTE:
Deaeration does not occur at engine idle, higher engine speeds are required. Normal driving will deaerate the cooling system.
To effectively deaerate the system, multiple thermal cycles of the system may be required.