* Air Pockets: Air trapped within the heater core's passages prevents coolant from flowing smoothly. As the coolant circulates and the air bubbles move, they create a gurgling or bubbling sound. This is often exacerbated when the heater is turned on, as the coolant flow through the core increases.
* Low Coolant Level: A low coolant level can lead to increased air in the system, contributing to the gurgling.
* Leaking Head Gasket (less likely, but serious): In more severe cases, a blown or leaking head gasket can introduce exhaust gases into the cooling system. These gases can become trapped, creating bubbles and a gurgling sound, accompanied by other symptoms like white smoke from the exhaust, overheating, and milky oil. This is a much more serious problem requiring immediate attention.
* Other Leaks: Small leaks in the cooling system can also introduce air, though this is less likely to cause a consistent gurgling.
What to do:
1. Check the coolant level: Open the coolant reservoir (when the engine is cool!) and check the level. If it's low, add the correct type of coolant (refer to your owner's manual).
2. Bleed the cooling system: If the coolant level is fine or after adding coolant, you likely need to bleed the cooling system to remove trapped air. This process varies depending on the Impala's specific engine, but often involves locating a bleed valve (usually on the engine block or radiator) and opening it while the engine runs to allow air to escape. Consult your owner's manual or a repair manual for your specific model. Some Impalas require a specific procedure to bleed the heater core.
3. Look for external leaks: Inspect the hoses, clamps, radiator, and water pump for any visible leaks.
4. If the gurgling persists or is accompanied by other symptoms (overheating, white exhaust smoke, milky oil): Take your Impala to a mechanic. A leaking head gasket is a serious issue that needs professional diagnosis and repair.
Don't ignore a gurgling heater core. While a simple air pocket is easily resolved, it could be a symptom of a more significant problem. Addressing it promptly can prevent more extensive (and costly) damage.
