汽车专业英语：第五章

1、Unit5 Cooling System Service Procedures5.1 Cooling System Operation5.2 Toyota Corolla Repair Manual5.1 Cooling System OperationThe cooling system controls temperature through heat transfer. Heat always moves from a hot object to a cooler object, so the cooling system transfers heat from the engine t

2、o the circulating coolant. Then the coolant transfers heat to the airflow through the radiator. Temperature control and heat transfer are based on the pressure of the system and coolant circulation(See Figure 5-1).下一页返回Pressures are highest at the water pump outlet and in the water jackets near the

3、combustion chambers.System pressure is lowest at the water pump inlet. Pressure is generated by the water pump and controlled by variable restrictions, like the thermostat, the heater control valve and valves in the radiator cap.The system also has fixed restrictions, such as orifices in the water j

4、ackets and passages in the radiator.返回上一页5.1 Cooling System Operation下一页返回To avoid the danger of being burned, do not remove the reservoir cap while the engine and radiator are still hot, as fluid and steam can be blown out under pressure.5.2.1 Inspect Cooling System for Leaks1.Fill the radiator wit

5、h coolant and attach a radiator cap tester.2.Warm up the engine.3.Pump the radiator cap tester to 118 KPa, and check the pressure does not drop.5.2 Toyota Corolla Repair Manual上一页返回5.2.2 Check Engine Coolant Level at ReservoirThe engine coolant level is checked when the engine is cold only.The engin

6、e coolant level should be between the LOW and FULL line.If low, check for leak and add Toyota Long Life Coolant or equivalent up to the FULL line.5.2 Toyota Corolla Repair Manual下一页上一页返回5.2.3 Check Engine Coolant Quality1.Remove the radiator cap (Please pay particular attention to be burned).2.Check

7、 if there is any excessive deposits of rust or scale around the radiator cap and radiator filler holes，the coolant should be free from oil.3.Reinstall the radiator cap.5.2 Toyota Corolla Repair Manual下一页上一页返回5.2.4 Inspect ThermostatThere are three ways to check the thermostat, one of which is Heat t

8、he Water.The thermostat is numbered with the valve opening temperature, as is shown in Figure 5-2.5.2 Toyota Corolla Repair Manual下一页上一页返回1.Remove the thermostat from engine and put it close.2.Immerse the thermostat in water and gradually heat the water (See Figure 5-3).3.Check the valve opening tem

9、perature (80-84).4.Check the valve lift(10 mm or more at 90) (See Figure 5-4).5.Check that the valve is fully closed when the thermostat is at low temperatures (below 77).5.2 Toyota Corolla Repair Manual下一页上一页返回5.2.5 Inspect Radiator Cap Sub-AssemblyIf the reservoir cap has contaminations, always ri

10、nse it with water.Before using a radiator cap tester, wet the relief valve and the pressure valve with engine coolant or water. 5.2 Toyota Corolla Repair Manual下一页上一页返回Using a radiator cap tester, slowly pump the tester and check that air is coming from the vacuum value.Pump the tester and measure t

11、he relief valve opening pressure.5.2 Toyota Corolla Repair Manual下一页上一页返回5.2.6 Coolant ReplacementA coolant change should be performed at every two years or 36,000 km.lDrain coolant( when engine is cold).lAdd coolant (always check the owners manual for the specifications for the recommended engine coolant).lInspect engine coolant leak.5.2 Toyota Corolla Repair ManualFig5-1 Cooling syste