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The cooling system
Introduction
Your engine needs a cooling system to protect it from self-destruction. Burning gases inside the cylinders can reach a temperature of 4500°F (2500°C) and produce enough heat to melt a 200 lb. engine block.
About one-third of the heat produced in the engine must be carried away by the cooling system. Some is utilized for heating the passenger compartment. Moreover, strange as it seems, your vehicle’s air conditioner produces heat in the process of cooing and dehumidifying the air. This heat must also be dispersed by the cooling system.
How the cooling system works
The main parts of the engine cooling system are the radiator, pressure cap, hoses, thermostat, coolant pump, fan, and drive belt (except on electric fan engines). The system is filled with coolant, which should be a 50-50 mixture of antifreeze and water. No mater where you live or how hot or cold the weather becomes, the mixture should be maintained the year around.
The water pump and engine cooling fan are mounted on the same shaft and driven by a belt connected to the engine. The pump draws coolant from the bottom of the radiator and forces it through passages surrounding the hot area—the cylinders, combustion chambers, valves and spark plugs. From there the coolant flows through a hose into the top of the radiator, then downward through tubes attached to cooling fins and surrounded by air passages. Heat is transferred from the coolant to air forced through the radiator passages by the fan and the forward motion of the vehicle.
Controlling the temperature
It’s important to get the coolant up to normal operating temperature as quickly as possible to ensure enough smooth engine operation, free flow of oil, and ample heat for the occupants. When the engine is cold, the thermostat blocks the passage from the cylinder head to the radiator and sends coolant on a shortcut to the water pump. The cooling fluid is not exposed to the blast of air from the radiator, so it warms up rapidly. As temperature increases, the thermostat gradually opens and allows coolant to flow through the radiator.
Cooling systems on older vehicles were limited to a maximum temperature of 212°F (100°C)—the boiling point of water. To get rid of the extra heat generated by more powerful engines, automatic transmissions, and air conditioning, modern vehicles have pressurized systems using a 50-50 mixture of antifreeze and water which enables them to operate at temperature up to 263°F (129.4°C) without boiling. At this temperature, plain water alone would boil away.
Transmission oil cooler
Automatic transmission oil is cooled by a small, separate radiator, usually located in the lower tank or alongside the main radiator. While the only purpose of the engine coolant is to keep the block and upper engine components cool, the transmission oil has three functions. It hydraulically operates the transmission, lubricates the transmission internal components and also keep the transmission within proper operating temperature range.
Most vehicles can benefit from the installation of a transmission oil cooler, especially if the vehicle is used to pull a trailer or for some other kind of heavy service.
Engine oil cooler
Some vehicles, particular high performance or diesel engines, are equipped with an engine oil cooler. The oil cooler can be located in one of the radiator tanks (similar to the transmission oil cooler), or mounted separately, near the front of the engine, on aftermarket applications. Also, there is usually an adapter mounted between the engine block and the oil filter. If the cooler is mounted in a radiator tank, heat is dissipated from the oil to the coolant. A separate oil cooler usually looks like a small radiator and heat is dispersed from the tubes and fins in the cooler to the air passing through the cooler. The purpose of the cooler is to reduce the temperature of the oil, preventing oxidation and increasing the oil’s lubricating and protecting properties. |
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