* Upper Heater Hose: This hose carries hot coolant *from* the engine to the heater core inside the vehicle. It's usually connected to a fitting on the engine near the thermostat housing. You'll likely find it near the top of the engine, possibly somewhat hidden behind other components.
* Lower Heater Hose: This hose carries cooled coolant *from* the heater core back to the engine. This one is typically found lower down, closer to the bottom of the engine and sometimes near the water pump.
Finding them precisely will require some visual inspection. Look for two rubber hoses of similar diameter that are connected to metal fittings. It might be helpful to consult a repair manual specific to your 2000 Chevy Venture. These manuals often have diagrams showing the exact location and routing of all hoses. You can find these manuals online or at auto parts stores.
Caution: The coolant in the system is hot when the engine is running. Allow the engine to cool completely before working near these hoses to avoid burns.
