It also provided an escape route for trapped air when first filling the system. This allows enough flow of cooling water to heat the thermostat when warming up. Conveniently this was also the hottest accessible part of the cooling circuit, giving a fast response when warming up.Ĭooling circuits have a small bypass path even when the thermostat is closed, usually by a small hole in the thermostat. As these thermostats could fail in service, they were designed for easy replacement during servicing, usually by being mounted under the water outlet fitting at the top of the cylinder block. As the liquid boiled inside the capsule, the capsule bellows expanded, opening a sheet brass plug valve within the thermostat. These capsules were made in the form of a cylindrical bellows. The first thermostats used a sealed capsule of an organic liquid with a boiling point just below the desired opening temperature. The development of the automatic thermostat in the 1930s solved this problem by ensuring fast engine warm-up. Research in the 1920s showed that cylinder wear was aggravated by condensation of fuel when it contacted a cool cylinder wall which removed the oil film. Although most vehicles now have a temperature-controlled electric cooling fan, 'the unassisted air stream can provide sufficient cooling up to 95% of the time' and so such a fan is not the mechanism for primary control of the internal temperature. Conveniently, both the sensing element of the thermostat and its control valve may be placed at the same location, allowing the use of a simple self-contained non-powered thermostat as the primary device for the precise control of engine temperature. This regulation is now carried out by an internal thermostat.

The internal combustion engine cooling thermostat maintains the temperature of the engine near its optimum operating temperature by regulating the flow of coolant to an air cooled radiator.

Element 3d 2.2 auto-normals