ENGINE 111 2.1.5.2 COMPONENTS A. RADIATOR The radiator used in ARIA is of cross flow type. The radiator is a heat exchanger used to dissipate the coolant heat. A radiator fan is used to create forced air circulation. Radiator consists of radiator core, inlet tank and an outlet tank. Cores are usually made of aluminum. The core has two sets of passages, a set of tubes and a set of fins attached to the tubes. The tubes run from inlet tank to outlet tank. Coolant flows through the tubes and air flows between the fins. The atmospheric air passing between the fins carries away the heat, which lowers the temperature of the coolant. B. THERMOSTAT It is located in a housing provided for it in the Engine block The thermostat controls the flow of coolant as follows. 1. During a cold start, thermostat does not allow coolant to flow to radiator since it is closed; instead the coolant flows through thermostat bypass outlet back to the engine .Thus short circuiting of radiator which helps in attaining engine working temperature in a very short period. 2. As soon as the coolant temperature reaches the opening temperature of the thermostat, the thermostat valve starts opening gradually and coolant starts flowing to the radiator. At the same time the thermostat by-pass starts closing gradually. 3. As the engine working temperature reaches thermostat full open temperature, the thermostat valve opens fully and thermostat by-pass valve closes completely. In this condition maximum quantity of engine coolant flows from radiator to water pump. SPECIFICATIONS • Thermostat start open temperature is 87º±2ºC at 0.1mm travel. • Full open temperature is 98º±2º C at 8.0 mm (Min.) travel. • Leakage through main valve (including jiggle pin) at room temperature and 1 kg/cm2 is 150cc/min. • Main flow rate of 165 LPM at 1.4 bar back pressure. Satisfactory operation of thermostat is very much essential for: • Efficient engine operation • Longer engine life. Checking procedure of thermostat: 1. Remove thermostat element from the housing. 2. Mount thermostat element in a suitable fixture and place the fixture in a vessel filled with water. 3. Fix dial gauge with its spindle on valve surface with a pretension of 0.5mm 4. Heat the vessel and measure the water temperature with proper thermometer. 5. Note down the temperature when dial gauge needles starts moving indicating valve opening. 6. Note down the water temperature for needle movement (for valve fully open position). 7. The opening temperature and fully open temperature as measured should be as per the mentioned specifications.
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