Air gets into the cooling system typically through:
* A leak: This is the most common cause. A small leak in a hose, radiator, water pump seal (though this usually leaks coolant, not introduces air), or head gasket can allow air to enter as coolant leaks out.
* Improper bleeding/filling: If the cooling system wasn't properly bled (removing air pockets) after maintenance or a coolant change, air can remain trapped.
* Low coolant level: A low coolant level leaves space for air to enter.
* Faulty radiator cap: A faulty radiator cap might not maintain the proper pressure, allowing air to enter.
* Cracked cylinder head or block: In severe cases, cracks can allow combustion gases (containing air) to enter the cooling system.
If your 1998 Chevy Venture is experiencing air in the cooling system, focus your attention on these areas rather than the water pump itself. A failing water pump will usually show other symptoms like overheating or a whining noise.
