After the second maintenance of Jiangling Shunda Guo Si, the engine sound became louder and louder. Why?

There are many factors that can make the engine sound louder. First, determine whether there are other abnormal noises or whether the sound is just as loud as the normal working sound (it is best to test multiple speeds). If there are no other abnormal noises, there are several common possibilities, such as psychological effects, excessive carbon deposition in the engine, air intake and throttle. In addition, when the maintenance period is approaching, the engine noise will also increase due to weak oil wear. If there are other abnormal noises, the situation will be more complicated and changeable. When some parts fail, they will make abnormal noise, such as water pump, belt tensioner, high pressure bag leakage, air inlet pipe or exhaust pipe leakage, etc. Some loose screws can also cause abnormal sound. Therefore, if you feel that the engine is getting louder and louder, you'd better go to a professional repair shop for repair. In the case of uncertainty, we should blindly draw conclusions so as not to cause unnecessary losses and waste time and energy.