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Lesson 1 How To Adjust The Valve Of Diesel Engine Do You Know

  • With the hot weather, many faults of the vehicle began to leak out. How to adjust the valve of Jiefang car when receiving the most problems? How many intake valves are there in Auman? Let’s talk about the valve today.
diesel engine

What is diesel engine clearance?

  • When the engine is working, the valve will expand due to the increase of temperature. If there is no clearance or the clearance between the valve and its transmission parts is too small in the cold state, diesel engine the thermal expansion of the valve and its transmission parts will inevitably cause the valve to close loosely in the hot state, resulting in air leakage in the compression stroke and power stroke of the engine, so as to reduce the power and even make it difficult to start in serious cases.
diesel engine
  • In order to eliminate this phenomenon, a certain clearance is usually reserved in the valve and its transmission diesel engine mechanism during the cold assembly of the engine to compensate for the expansion of the valve after heating. This clearance is called valve clearance.

Why adjust the diesel engine clearance?

  • Because the valve is in contact with the cylinder block, the cylinder block emits a lot of heat when moving, and after the valve is in contact with the cylinder block, the heat will be transferred to the valve, so as to increase the elongation of the valve.
diesel engine
  • If the valve clearance is not reserved in advance, when the vehicle is in cold state, the valve is in close contact with the cylinder block. When the cylinder block becomes hot and the elongation of the valve increases due to thermal expansion, the valve will top the cylinder block or the valve itself. 
  • Therefore, appropriate valve clearance should be reserved. Reasonable valve clearance is an important prerequisite to ensure the normal and stable operation of the engine.
  • Basic conditions of diesel engine valve clearance adjustment
  • The basic conditions for valve clearance adjustment of diesel engine are:
    Shutdown, cold running and valve closing; The valve closing state of diesel engine is the valve clearance adjustable position, which is referred to as valve position for short.
diesel engine
  • The principle of valve adjustment of diesel engine is that the intake valve is cooled by fresh air and the temperature is between 300 ℃ and 400 ℃, while the exhaust valve is washed by high-temperature exhaust gas and the temperature is between 600 ℃ and 800 ℃. 
  • Therefore, the temperature of exhaust valve is higher than that of inlet valve and the thermal expansion is also greater than that of inlet valve. Therefore, generally, the exhaust valve clearance is larger than the inlet valve clearance.
  • What is the effect of improper adjustment of diesel engine valve clearance?
    Improper adjustment of valve clearance not only affects engine power, fuel consumption, wear, but also has noise.
  • Hazards of excessive valve clearance
  • ① The valve opening decreases, the intake and exhaust resistance increases, the intake volume is insufficient, the power is reduced, and the exhaust is not smooth.
  • ② Increase the impact of the valve drive group on the valve group, resulting in large abnormal noise.
  • ③ There will be a “rebound” phenomenon, that is, the valve will jump up again after it is seated.
  • ④ There will be “flying jump”, that is, the law of valve rise and fall and the opening and closing of valves do not meet the original design requirements, so that the valve timing changes and affects the power and economy.diesel engine
diesel engine
  • Harm of too small valve clearance
  • It will cause the valve to close loosely, resulting in air leakage, easy to ablate the working surface of the valve and valve seat, and also affect the power and economy of the diesel engine.
  • After understanding these, we have compiled various diesel engine adjustment methods and corresponding standard values, including Weichai, Xichai, Cummins, heavy truck, Yuchai and other engines. If you can’t adjust them, you must collect them.
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