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Cooling Systems

Cooling Systems. Cooling Systems. The cooling system removes excess heat to keep the inside of the engine at an efficient temperature, about 200 o F (94 o C). Animation: Cooling System. Coolant Flow.

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Cooling Systems

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  1. Cooling Systems

  2. Cooling Systems The cooling system removes excess heat to keep the inside of the engine at an efficient temperature, about 200o F (94o C). Animation: Cooling System

  3. Coolant Flow Coolant flows through the water jackets where it absorbs heat. It then flows through the radiator where heat is transferred to the air passing through. The amount of flow is determined by the water pump. The flow direction is controlled by the thermostat.

  4. Cold Engine When an engine is cold, the thermostat is cold. Coolant flow is through the bypass hose and the water jackets. This allows the engine to warm up evenly.

  5. Warm Engine The thermostat opens when the engine warms up. This allows coolant to circulate through the radiator and the water jackets.

  6. Thermostat Operation The spring in this thermostat has closed the valve. When it gets hot, the heat motor will push the valve open. Animation: Thermostat Operation

  7. Hoses Reinforced rubber hoses transfer the coolant from the engine to the radiator, coolant reservoir, and heater core.

  8. Radiator Operation The hot coolant flows through the radiator tubes and heat is transferred to the fins and then to the air passing through radiator.

  9. Radiator Types Older vehicles used downflow radiators with the coolant flowing from the top to the bottom. Modern vehicles use crossflow radiators with the coolant flowing from one side to the other.

  10. Radiator Cap The upper gasket prevents coolant from escaping to the outside. The lower gasket keeps a pressure in the radiator. The cam lock pushes the two gaskets against the sealing surfaces when the cap is installed. The safety stop prevents the cap from being opened too quickly. Animation: Pressure Cap

  11. Radiator Pressure Radiator pressure results from the expansion of the coolant as the engine warms up. Coolant volume increases about 10% as the temperature increases from 70 to 180o F (21 to 82o C). The radiator cap creates the pressure by holding the coolant in the radiator. The coolant’s boiling point increases about 3o F for each psi increase in pressure.

  12. Coolant Recovery Reservoir When the engine warms up, the radiator cap allows the expanding coolant to flow into the coolant recovery reservoir. When the engine and coolant cool down, the coolant returns to the radiator and water jackets through the vacuum valve in the cap.

  13. Radiator Cap Types These caps are the same except for the vacuum valve. This valve opens to allow coolant to return from the CRR. The gravity vacuum valve opens much easier.

  14. Radiator Air Flow Air flows through the openings at the front of the vehicle, through the radiator and other heat exchangers, and exits past the engine. The fan with shroud assists the natural flow when the vehicle goes slow or is stopped.

  15. Fan and Fan Drive Most rear wheel drive vehicles use a mechanically driven fan that is mounted onto the water pump.

  16. Fan Clutch The fan clutch allows the use of a large fan that can be driven at slower speeds. A thermal fan clutch senses temperature and will drive the fan only when it becomes necessary.

  17. Drive Belt The water pump and fan are driven by a flexible accessory drive belt that is driven by the crankshaft pulley.

  18. Electric Fans Most front wheel drive vehicles use fan that is driven by an electric motor. This fan assembly includes the motor, fan, and shroud. Some vehicles use two fans and some of these have two speeds.

  19. Coolant and Antifreeze Coolant is a mixture of antifreeze and water. Antifreeze lowers the freezing point and raises the boiling point. Coolant also protects the system from rust and corrosion.

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