Q: Car has little vibration. I wonder that is problem cause of power steering wheel fluid or other reason.

Hello. If you have a vibration in the steering, it more than likely has nothing to do with the power steering fluid. The pump would make noise if it needed the fluid also. If it vibrates when hitting the brakes, then you more than likely have a warped rotor. If it vibrates at higher speeds, then it is more than likely a tire balance problem. It can also be a worn out steering part or a bad engine mount or axle. All of these parts need to be checked out prior to replacing anything. If you are looking to get this checked, consider YourMechanic, as a certified mechanic can come to your home or office to inspect your brakes, steering, and suspension to detect the cause of the vibration.