Fault performance: There is a narrow space between the inlet and exhaust valve seat of the Cummins QSC Cylinder Head and the cylinder head wall, which is the most prone to cracks in use. When the cylinder head has a slight crack, the exhaust pipe emits smoke. After the crack gradually expands and increases, helium is blown into the water tank to form bubbles. The cooling water seeps into the cylinder, making the engine not start well, white smoke, the sound is not good, and the power is reduced.
Causes and precautions: (1) The Yamz 238 Cylinder Head gasket is not well installed between the cylinder head and the cylinder block. Due to the inaccuracy of the position of the holes, the flow of the cooling water is reduced, which affects the cooling effect and increases the machine temperature. Therefore, when installing the cylinder head gasket, be sure to check the alignment holes carefully. Cylinder mats with too many hole positions can not be used. (2) When the temperature of the machine is high, the cooling water is added. Cracks are caused by sudden heat quenching. Therefore, it is not allowed to add cold water to the water tank when the temperature is high. In the operation method, it is strictly forbidden to start the engine and then add cooling water. (3) Hard water is often used. Since the hard water is easy to generate scale, and the cooling system is not cleaned in time, the cooling capacity of the cooling system is lowered, which is liable to cause cracks in the cylinder head. Therefore, soft water must be used according to technical requirements and the cooling system should be cleaned in time. (4) Always use a decompression mechanism to park. Stopping with this method of operation causes the engine to draw in too much cold air at high temperatures, causing the cylinder head to suddenly cool and crack. Therefore, under normal circumstances, do not use a pressure relief mechanism to stop.
Cylinder cover crack inspection method: commonly used observation method, fluorescence detection method, hydraulic pressure test and magnetic flaw detection method.
Repair of cracks: repair with weld repair or glue. In addition, it can also be repaired by various repair methods and by various techniques such as pliers, welding and bonding. After the cylinder head is repaired, it must pass the hydrostatic test. Under the pressure of 0.3~0. 4 MPa, the leakage is not acceptable for 3 min. Check the warpage of the plane should not exceed 0.15mm. Milling is required when the cylinder head flatness is greater than 0.15 mm. The cylinder head is placed on a flat milling machine, and the plane is milled. The depth of the knife is 0. 25 mm, which is milled at one time.
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