Coolant: Testing and Inspection

COOLANT - LOW LEVEL AERATION
If the coolant level in radiator drops below top of radiator core tubes, air will enter cooling system.
Low coolant level can cause thermostat pellet to be suspended in air instead of coolant. This will cause thermostat to open later, which in turn causes higher coolant temperature. Air trapped in cooling system also reduces amount of coolant circulating in heater core resulting in low heat output.