Smoke coming out from under the hood of a car means the engine is overheating, according to CarsDirect and HowStuffWorks. It can be caused by a variety of problems, but is most commonly associated with a malfunction in the cooling system, more specifically the radiator.
There are seven common repairs to a car's cooling system. All of these repairs are for problems that cause a car to overheat and produce smoke from under the hood.
A failed thermostat is the most common problem that causes a vehicle to overheat. The thermostat is a valve that controls the amount of coolant that flows through the radiator. A leaky radiator hose can cause coolant to leak and overheat the engine. The hoses connect the radiator to the engine and allow coolant to flow through them. If air becomes trapped in the cooling system, it can obstruct the coolant flow.
There are also leaks in the radiator itself. These leaks often produce steam or bubbles. A failed water pump causes water to not circulate properly through the engine and it can no longer regulate the temperature efficiently. If there is an obstruction in the cooling system, a car can overheat. Obstructions are caused from body damage produced by an accident or from bent fins. Radiator fans fail, causing an engine to overheat. The fans pull air through the radiator to keep it cool. It is best to add coolant or antifreeze to the vehicle's cooling system to keep it from overheating.