Most common cause is a bad water pump, or harmonic balancer. Other possible causes are bad motor, bad supercharger, cracked flyweel, or in rare instances a bad torque converter.
A little kid in the trunk with a hammer
it could be your valves or your engine
Could be the CV joint is dry or has failed.
u joint
many many things, Loose lug nuts which lets wheel make knocking noise. Engine will make a knocking noise if it is really low on oil. Some timing belts make a knocking, slapping noise just before they break.These are just a few examples . Have someone ride in car with you as you duplcate the noise and see if they can determine which part of the vehicle it is coming from.
knocking noise
It's the spirit of the car knocking on the side saying "HELLO??? TAKE ME TO A MECHANIC!"
rack and pinion
Can be a number of things, the first thing to check would be the Subframe Bushes
tie rods
There could be loosened internal mounts (connecting rods, pistons, pins, crankshafts or other related parts) in the compressor causing the banging or knocking noise. A simple call to a technician should resolve the issue.
Could be the resonator