Can't see it; can't hear it. You're in a better position to figure out the cause. A loose or worn belt is common but you didn't say if the engine has to be running, if the car has to be moving, if the noise only occurs when turning the steering wheel, if the noise changes with changes in engine speed, if the noise goes away when you press the brake pedal, if it only occurs when you drive over bumps, etc. You need to find a live person to open the hood, listen to the noise, and inspect likely causes.
Thursday, March 21st, 2013 AT 6:47 PM