The function of the Ashland radiator is to dissipate heat from the hot water circulating in the cooling system. It normally consists of a header or top tank and a bottom or receiving tank, with a core, usually of metal tubes, between them.
Hot water enters the header tank through the thermostat from the water jacket and flows through the core, where it gives up its heat. The tubes are fitted with fins to provide a greater contact area for the cooling air.
The cooled water passes into the receiving tank and is then returned to the engine through the water pump.
In many radiators, space is left between the surface of the water and the top of the header tank for expansion of water. Any surplus water or steam escape through the overflow to the ground.
In later designs, the overflow is taken to an extra expansion tank away from the radiator. As the water cools, it is drawn back into the header tank.
This is known as a sealed system. Since no water is allowed to escape, the system is sometimes filled as the factory with a mixture of water and antifreeze. As long as the cooling system remains leak proof, no further attention, other than the occasional inspection, is called for.
The Role Antifreeze Plays in the Radiator
In cold weather, freezing water can cause a burst in the radiator of a car which has been left standing. It is equally possible for a radiator to freeze and burst when a car is being driven – even though the water in the engine may be boiling. This is because the thermostat prevents hot water from the engine circulating through the radiator until the engine reaches a set temperature.
If a car is driven through the cold air, water in the radiator can freeze before the thermostat valve has opened.
Freezing of the radiator can be avoided by adding a chemical – usually glycol and inhibitors.
The ASTM has prepared a specification for antifreeze solutions, and motorists should ensure that the antifreeze they buy carries their approval and that it is used according to the instructions on the product. The indiscriminate mixing of different solutions should be avoided.
Unless otherwise specified, antifreeze may be left in the cooling system all year round as the inhibitors give protection against corrosion.
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Speeding the Flow
In most engines, the water pump is mounted on the front of the cylinder block and is driven by the fan belt. It draws cool water from the bottom of the radiator and delivers this into the engine’s water jackets. Water heated by the engine then flows through the cylinder head and the thermostat back into the radiator.
A small flow to the vehicle’s heater, and in some makes to the induction manifold, is returned to the radiator without passing through the thermostat.
The impeller of the pump is a rotating disc carrying vanes, which fling the water outwards against the pump’s casing by centrifugal force and impel it forwards into the water jacket. A seal prevents water from escaping along the impeller shaft.
When the thermostat restricts circulation of the coolant through the radiator, the impeller still revolves, circulating water around the engine only, through the bypass pipe.
Any squeak from the water pump seal is usually only temporary. It should not be treated, as some garages advise, by mixing soluble oil that is also referred to as cutting oil with the radiator water. Minerals in the soluble oil could rot the rubber hoses in the cooling system.
How Do Air-cooled Engines Work?
Air cooling without proper ducting and fan assisted circulation cannot overcome the difficulty of cooling all cylinders evenly, particularly with in-line engines.
The cylinders at the rear of the engine would get little cooling effects from the flow of air through the grille at the front of the car.
To overcome this, air cooled engines use a fan to force a cooling air stream over the cylinders. Thermostatic control adjusts the airflow to suit temperature conditions.
Fins on the cylinders and cylinder heads increase the surface exposed to the air. Since certain areas of the cylinders and heads, such as the exhausts ports of the combustion chambers, develop more heat that must be dissipated, the fins are usually bigger in those areas than elsewhere on the engine.
Heat always flows from a large mass of the material to the thinnest section exposed to a cooler medium. Fins are therefore tapered, to promote the dissipation of heat.
Somehow an air cooled engine is a lot noisier than a water cooled engine, in which the water jacket dumps down a great deal of the engine noise.
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