Here's why a non-functional impeller would cause this problem:
* No Coolant Flow: The impeller is the part of the water pump that creates the flow of coolant. If it's broken, seized, or simply not spinning, the coolant remains stagnant, leading to overheating in some cases (as the engine generates heat with no way to dissipate it) and in others (like yours), no heat at all because there's no flow to transfer that heat.
* Airlocks: A non-functioning pump can also lead to airlocks in the system, further hindering coolant circulation.
How to check if the impeller is the problem:
* Visually inspect the water pump: If you're comfortable working on your vehicle, you can remove the serpentine belt and check if the impeller spins freely. A seized or damaged impeller will be obvious.
* Feel for flow: With the engine running, carefully (and briefly) touch the upper and lower radiator hoses. You should feel a significant difference in temperature between the two. If both are cold or equally warm, there's likely little to no coolant flow. Be extremely cautious doing this; coolant is hot!
* Inspect the coolant itself: Look for discoloration, rust, or other debris that might indicate pump failure.
If the impeller is the problem, you'll need to replace the entire water pump. It's generally not cost-effective to replace just the impeller.
Before replacing the water pump though, consider these possibilities, even after replacing the thermostat:
* Thermostat installed incorrectly: Double-check the thermostat installation.
* Air in the cooling system: Bleed the cooling system properly to remove any air pockets that might be hindering circulation. This sometimes requires a specific procedure depending on your vehicle's make and model.
* Head gasket failure (less likely but possible): A blown head gasket can prevent proper coolant flow and lead to similar symptoms. This would typically result in other issues, such as white smoke from the exhaust or coolant in the oil.
In short, a faulty impeller is a strong possibility, but ruling out the other, less likely issues is advisable before committing to a water pump replacement.
