The purpose of a thermostat in an engine cooling system is to

prevent the coolant from boiling

allow the engine to warm up quickly

indicate the coolant temperature

pressurize the system to raise the boiling point

engine piston

engine cylinder

lubricating oil

jacket cooling water

carburettor - air cleaner - intake manifold - intake ports - cylinders

air cleaner - carburetor - intake ports - intake manifold - cylinders

air cleaner - intake manifold - carburetor - intake ports - cylinders

air cleaner - carburetor - intake manifold - intake ports - cylinders

controls the engine's air intake volume

reduces the engine's air intake noise

prevents rain water from entering the engine

prevents dust and other foreign matter from entering the engine

promotes the mixture of air and fuel

reduces intake noise

cools the intake air to a suitable temperature

distributes intake air equally to the cylinders