A serviceable engine in working order must necessarily make noise. Everyone has their own noise. A good petrol hums rather quietly. In contrast, a diesel engine has a sharper sound. However, sometimes the engine can make noise with an unusual sound.
There can be several reasons for abnormal engine noise. The most common of these is the presence of a worn-out bearing of the mounted aggregator. To check this, remove the drive belts and check all the pulleys with your hands. The bearing must be replaced if the balls roll freely on the tracks and if the pulley independently makes more than one revolution. If it only makes one revolution, change the lubricant. Another cause of engine noise may be a leak in the exhaust ducts. This can happen as a result of even a small traffic accident. If the air bag was removed from the car when replacing the fender, then the engine noise will be perfectly heard in the cabin. Continuing the topic of tightness and engine noise, it is worth noting that the reason may lie in a leaky exhaust tract. You can check this by the smell characteristic of the exhaust gases, as well as by the presence of smoke and traces of soot near the cracks. You can also just put your hand. If this theory is correct, the palm will burn a little. The reason for the engine noise can also lie in the drive belts, if they deform when they hit the pulley. At idle, they can emit a characteristic creak or squeak. Test this theory as you start the engine and disengage. Pour water onto each of the belts at the same time. If the noise decreases, be sure to replace them. The problem may also lie in the tension of the belts. If the tension is loose, the belt will vibrate and the bearings will slide over the pulley. When the tension is very strong, there is a large load on the bearings, which can also generate noise, or noise can also appear due to a malfunction of the water pump. To check this, remove the toothed belt and rotate the pump gear. It must be replaced if there is jamming during pumping or noise. It is also worth replacing the pump if there is any backlash.
