The Thermo-Cap radiator cap indicates the coolant temperature with its own inbuilt calibrated thermometer. This can be useful information prior to cap removal. The temperature probe does not need to be in contact with the coolant in order to indicate the correct temperature. Thermo-Cap is also equipped with a coolant recovery reclamation valve so it is compatible with cooling systems that have an overflow reservoir. Thermo-Caps can also be used with cooling systems that do not have an overflow reservoir.