A cooling apparatus for an engine comprising: a) a coolant reservoir comprising a coolant line outlet port; b) a tank for holding an aqueous urea solution for injection into an exhaust system of the engine; c) a coolant line for transferring a coolant fluid discharged from the coolant reservoir via the coolant line outlet port to the tank to enable, in use, heat exchange between the coolant fluid and the aqueous urea solution contained in the tank; d) a coolant control valve located on the coolant line for controlling flow of coolant fluid along the coolant line to the tank; and e) a filter for filtering the coolant fluid being discharged via the coolant line outlet port; wherein the filter comprises a filtering portion that is located within an interior of the coolant reservoir so that the coolant fluid is filtered within the coolant reservoir before the coolant fluid enters the coolant line.