What are the causes of metal friction noise when a car is driving at low speed?

[DelAndrew]

Here are the reasons why a car produces metal friction noise when driving at low speed: 1. Friction noise between the brake disc and pedal. 2. Damaged brake pads, which are recommended to be replaced. The following are the methods to identify car noises: 1. Correctly distinguish between normal noises and abnormal noises: When a car is working, the vibrations of various mechanisms will produce multiple types of noises, but the presence of noise does not necessarily indicate a fault in the car. To avoid unnecessary disassembly, it is essential to first distinguish between normal noises and abnormal noises. Normal noises include the normal vibration sounds of various system components, the impact sound of gears during gear shifting, the intake and exhaust sounds when using gas as the working source, and gear meshing noise, among others. Abnormal noises can be categorized into minor noises, general noises, and severe noises based on their impact on the car's performance. Minor noises generally have low volume, cause little wear on components, and show no significant changes over a long period. Such faults can still allow the car to operate normally without repair. General noises have a noticeable impact on the car's performance but can maintain its main technical performance in the short term. These noises usually have a higher volume and cause greater wear on components, so they should be repaired promptly. If such noises occur during driving, temporary measures can be taken. Severe noises, such as severe knocking sounds from the crankshaft bearings or connecting rod bearings accompanied by a drop in lubricating oil pressure, significant gear impact sounds from the transmission, and strong vibration sounds from the differential, have a serious impact on the car and may cause or have already caused severe damage to components. Such faults must be taken seriously, and the car should be stopped immediately for inspection. Driving under such conditions is strongly discouraged, as it can easily lead to major mechanical accidents. 2. Diagnostic conditions: When diagnosing abnormal noises in a car, it is important to create good diagnostic conditions and try to eliminate interference from other noises to avoid affecting the accuracy of judgment. It is best to consciously amplify or reduce the sound, and the diagnostic site should be kept quiet to minimize interference from human factors.