What's wrong with the loud engine? How to solve it?

First of all, let's talk about the common phenomenon of loud valve sound. What's the reason for loud valve sound? How to solve it?
a. If it is a hydraulic tappet type cylinder head, the loud sound of the valve may be caused by insufficient oil pressure or lack of oil, resulting in poor lubrication of the engine oil, which may cause rattling noises on the valve tappets!
It may also be caused by damage to the hydraulic tappet and excessive clearance caused by its own fault!
How should we address this situation? First, check whether there is a lack of oil, then measure whether the oil pressure is normal, and finally remove the valve cover to check whether each hydraulic tappet has a problem!
b. Another type of valve is gasket or adjustable
If this kind of clicking noise occurs, first of all, it must be ruled out whether it is caused by poor lubrication caused by insufficient oil!
Then comes the clearance issue! The gasket is difficult to adjust, as long as the adjustable valve is adjusted to the normal range!
2. The belt makes abnormal noise! This includes the squeaking of the belt itself, as well as the noises made by compressors, tensioner wheels, generators, booster pumps, water pumps, fall wheels, and so on!
For example, if the tensioner wheel bearing makes a strange noise, it may be that the bearing is broken or out of oil! Is there a sound of iron contacting with iron when the water pump bearing is broken!
3. If there is a problem with the clutch or transmission of a manual transmission car, you may also hear loud engine noise!
4. Another one is the sound generated by engine resonance!
Generally, the sound heard inside the driver's cab is quite obvious and can hardly be heard outside!
This situation is generally a problem with the engine floor mats, and the engine noise is transmitted directly to the cab without being cushioned by the floor mats! This involves directly checking the floor mats and checking to see if any parts on the engine come into direct contact with the vehicle shell!
5. The engine knocking makes a very clear and crisp sound from the engine bearing shells!
This is usually caused by insufficient oil lubrication, which usually requires an overhaul of the engine!