Hello - the rhythmic knocking (https://www.yourmechanic.com/article/what-does-it-mean-when-an-engine-knocks) you hear could be something driven by the serpentine belt (i.e. AC compressor) or the belt itself. It is also possible that this an internal noise - like the timing chain (https://www.yourmechanic.com/article/how-long-does-a-timing-chain-last), which is...
