A coolant flow measurement device includes a coolant flow circuit, a cooling system, a purge system, a variable speed fluid pump, a differential pressure gage and a primary flow meter. The coolant flow circuit may be attached to a an HVAC system of the vehicle such that coolant may be circulated through the HVAC system of the vehicle. The cooling system may cool the coolant in the coolant flow circuit. The purge system may be used to purge air from the coolant flow circuit. The variable speed fluid pump may be operable to balance the fluid pressure between the device inlet and the device outlet. The primary flow meter may be operable to measure the coolant flow in the coolant flow circuit. The differential pressure gage measures a pressure differential between the device inlet and the device outlet.