The thermostat on a 1999 Volkswagen Cabrio is located on the side of the engine closest to the radiator. It is a small, cylindrical device with two wires coming out of it, usually in a brass housing and secured with two bolts. To find it, trace the upper radiator hose from the radiator to the engine block; follow the hose until you arrive at a round or square shaped device about three to four inches wide. That is the thermostat.
