Cold Start Noise
WARNING: This page is about a different car, the 2006 Ford Pickup, 2006 Ford F550 Super Duty, 2006 Ford F450 Super Duty, and 2006 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Cold start noise is the airborne noise generated by pump cavitation when hydraulic fluid does not flow freely through the suction hose from the reservoir to pump. Zip is primarily a cold weather start-up phenomenon. Some noise during an extremely cold start (-12.2°C [-10°F]) is normal and should improve as the steering system warms up (usually within 60 seconds).