Cooling system

A cooling system for an internal combustion engine, the cooling system comprising:

• a cooling passage provided within an engine housing of the engine, the cooling passage configured to carry a bulk flow of coolant to cool the engine housing, wherein the bulk flow of coolant within the cooling passage is driven by convection or a pump;
• one or more additional cooling passages provided within the engine housing, the or each additional cooling passage configured to introduce a flow of coolant midstream into the flow of coolant in the cooling passage;
• and
• one or more additional cooling passage pumps configured to pump coolant within the additional coolant passages;
• wherein the engine housing comprises one or more high temperature regions, which are at a higher temperature than one or more low temperature regions of the engine housing;
• wherein the additional cooling passages are configured to direct the introduced coolant towards the one or more high temperature regions;
• wherein the bulk flow of coolant within the cooling passage is driven only by convection;
• wherein the bulk flow of coolant within the cooling passage is at a first velocity;
• and
• wherein the additional cooling passage pumps are configured to pump the coolant in the additional cooling passages at a second velocity, which is greater than the first velocity.