Evaporation of lubricating oil that lubricates the piston and cylinder wall is also another reason of under cooling. Under cooling also keeps the engine in correct position and increase the life of the engine. If the engine gets warmed up excessively, it should be cooled so as to keep the correct alignment of the engine. Over cooling results in the increase of viscosity of the lubricating oil, which in turn result in the increase of friction between the moving parts. Both under cooling and over cooling have individual disadvantages. And if the engine is over heated it is to under cool. Getting the engine too much cooled is called overcooling. It should not be too cooled or too heated up. So antifreeze usuallyĪntifreeze should not be drained each summer it can normally be left in for two or three years.Effects of under cooling and over cooling:Įngine should be cooled within a particular temperature limits.
Water expands when it freezes, and if the water in an engine freezes it can burst the block or radiator. When the engine stops and cools, the valve closes again. When the engine warms up, the wax melts, expands and pushes the valve open, allowing coolant to flow through the radiator. The thermostat has a valve worked by a chamber filled with wax. To let the engine warm up quickly, the radiator is closed off by a Other cars have an electric fan, also switched on and off by a temperature Worked by a temperature sensitive valve that uncouples the fan until the coolant temperature reaches a set point. The fan may be driven by the engine, but unless the engine is working hard, it is not always needed while the car is moving, so the When the car is moving, this happens anyway but when it is stationary a The radiator needs a constant flow of air through its core to cool it adequately. , from which it is sucked back into the engine when the remaining liquid cools. Later cars have a sealed system in which any overflow goes into an The system needs topping up from time to time. Of this type there is a continual slight loss of coolant if the engine runs very hot. Excessive pressure opens the valve, and coolant flows out through an overflow pipe. The extra pressure is limited by the radiator cap, which has a pressure In the system, which raises the boiling point. The risk of boiling is avoided by increasing the In an engine at its ordinary working temperature, the coolant is only just below normal boiling point. On older cars the tubes run vertically, but modern, low-fronted cars have crossflow radiators with tubes that run from side to side. The tubes pass through holes in a stack of thin sheet-metal fins, so that the core has a very large surface area and can lose heat rapidly to the cooler air passing through it. , and has a top and bottom tank connected by a core a bank of many fine tubes. The radiator is linked to the engine by rubber Its natural tendency is to flow upwards, and the pump assists circulation. Usually the pump sends coolant up through the engine and down through the radiator, taking advantage of the fact that hot water expands, becomes lighter and rises above cool water when heated. Unwanted heat is passed from the radiator into the air stream, and the cooled liquid then returns to an inlet at the bottom of the block and flows back into the channels again. , drives hot coolant out of the engine to the At the top of the cylinder head all the channels converge to a single outlet. Have interconnected coolant channels running through them.