一辆 JN150汽车柴油发动机出现水箱中有油污现象。驾驶员反映,出现油污后,发动机无其他异常现象,机油中无冷却水进入,排气烟色也正常。更换气缸盖和气缸垫,油污依旧。根据故障现象和经验,故障很可能是由于气缸上部有裂纹所造成。卸下缸盖,仔细检查气缸垫和缸体、缸盖平面,没有冲缸垫现象。将活塞转到下止点位置,逐缸检查气缸套内表面,无明显裂纹。再将缸套逐一拉出,并用氧—乙炔焰检查(当用氧—乙炔焰加热缸套外圆周面时,如有裂纹,在缸套内表面能很明显地看到缸套 A JN150 car diesel engine oil tank appeared in the phenomenon. The driver reflected that after the oil appeared, the engine did not have any other abnormal phenomenon, the engine oil did not enter into the cooling water and the exhaust smoke color was also normal. Replace the cylinder head and cylinder pad, the oil is still. According to the phenomenon and experience of failure, the failure is likely to be caused by cracks in the upper cylinder. Remove the cylinder head, carefully check the cylinder pad and cylinder block, cylinder head plane, there is no red cylinder pad phenomenon. The piston to the bottom dead center position, by cylinder check cylinder liner inner surface, no obvious cracks. And then the cylinder one by one pulled out and check with oxygen - acetylene flame (when using oxygen - acetylene flame heating cylinder liner on the outer circumferential surface, if cracks in the liner surface can be clearly seen cylinder liner