The temperature difference between the top and bottom radiator hoses will depend on several factors, including the engine’s operating temperature, the cooling system’s efficiency, and the amount of coolant flow through the system.
In a properly functioning cooling system, the coolant is circulated from the engine to the radiator via the upper radiator hose, where it is cooled by airflow and then returned to the engine via the lower radiator hose. The temperature difference between the two hoses will typically be in the range of 10-20 degrees Fahrenheit (5-11 degrees Celsius) under normal operating conditions.
If the temperature difference is significantly greater than this range, it could be an indication of a problem with the cooling system, such as a clogged radiator or a malfunctioning water pump. In such cases, it is recommended to have the cooling system inspected by a qualified mechanic.