单项选择题

Which of the following precautions must be taken if an electric immersion heater is used to keep the coolant in a diesel engine warm during the time the engine is secured?（）

A.The coolant temperature must be maintained at 180℃
B.The thermostatic bypass valves must be manually opened before the engine is started
C.The pressure cap must be removed while the engine is secured
D.Electrical power to the heater must be secured before the cooling system is drained

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单项选择题

Which of the following statements is true regarding the installation of piston rings on two-stroke/cycle, diesel engines as compared to four-stroke/cycle, diesel engines?（）

A.In a two-stroke/cycle engine, the rings run hotter, requiring the end gap to be greater
B.Some provision must be made in a two-stroke/cycle engine to keep the rings from binding in the ports
C.No gap is required to exist between the ends of the ring when cold in a two-stroke/cycle engine, but a small gap is required in a four-stoke/cycle engine
D.The gaps should be staggered on either side of a piston in a two-stroke/cycle engine, while staggering is not necessary in a four-stroke/cycle engine

单项选择题

If a crankcase explosion occurs in a diesel engine, which of the listed actions should be taken?（）

A.Open the crankcase immediately to check for damage
B.Apply fire fighting water through the crankcase breather
C.Allow the engine to cool before opening the crankcase
D.Assume that there is no damage to the crankshaft

单项选择题

A substance found in residual fuels which tends to cause exhaust valve corrosion and grooving, is（）

A.carbon
B.vanadium
C.calcium
D.hydrogen