1. The generator belt had abnormal sound some time ago, which was larger than the abnormal sound that occurred in the previous winter and continued. When going to the 4S shop for maintenance, ask the master to check whether to replace it and see where the problem went.
The master took off the belt and inspected several wheels, but did not point out any special problems. After reinstalling it and using special lubricating oil, there was no abnormality. From July 10 to the present, there has been no abnormal sound after ignition, and there has been no abnormal sound throughout the driving process.
I asked, I need 3K + to replace a set in 4S. It’s more expensive than I expected. I checked the Internet and found that Gates ‘discount at Jingdong’s self-operated store also cost 1100, and Gates’ flagship store on Taobao cost 598. They both asked customer service to adapt them to their own cars.

Ask: What causes this abnormal sound? How many years and mileage can a generator set (one belt, one tensioner, two pulleys) generally last?
Are the parts of my car worn out and need to be replaced? Is it installation or what problem caused it?
What should we do now?

2. Inspection during maintenance pointed out that the rear brake pads are 3mm and the front 4mm, and it is recommended to replace them.
The car is eight years old, but the mileage is only about 40,000 kilometers. Should we replace it until the police call or replace it in advance in the near future? About how much mileage should the brake disc be replaced?
I checked the self-operated area of Jingdong and found that the prices were 960 yuan and 750 yuan respectively. Is it better to buy the original one or use another brand that does not drop black brake powder? The premise is that it will not affect the performance of the brake, nor will it significantly affect the comfort. Being clean and not losing powder is secondary. I hope you will be generous in sharing and advising.

Due to the long age, four tires were replaced. 4K+, exactly the same model as the original tire.