Diagnosis And Testing: Aeration

Low coolant level in a cross flow radiator will equalize in both tanks with engine off. With engine running and at operating temperature, the high pressure inlet tank runs full and the low pressure outlet tank drops, resulting in cooling system aeration. Aeration will draw air into the water pump resulting in the following:

• High reading shown on the temperature gauge.
• Loss of coolant flow through the heater core.
• Corrosion in the cooling system.
• Water pump seal may run dry, increasing the risk of premature seal failure.
• Combustion gas leaks into the coolant can also cause aeration.