Cold Start Noise
WARNING: This page is about a different car, the 2007 Ford Pickup, 2007 Ford F550 Super Duty, 2007 Ford F450 Super Duty, and 2007 Ford Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
Cold start noise is the air-born 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).