A 2008 Audi A3 that exhibits a loud cracking or rubbing noise when the steering wheel is turned may have an issue with a front strut shock absorber cap that is chafing on the plastic cap of the strut.
If, when the car is listed on a hoist, the noise disappears, it’s likely that the boot is not properly secured, incorrectly installed or has deformed.
After replacing a damaged boot, if needed, brush silicon grease onto the contact surface of the plastic cap of the strut. Attach the boot correctly on the slots of the upper mount and the bottom of the damper. Slight deformations of the boot can be pressed out at room temperature.